DEPABTMENT OF THE INTEBIOK

BULLETIN

OF THE

GEOLOGICAL SUK VET

TSTo. 159

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1899

UNITED STATES GEOLOGICAL SUEVEY

CHARLES D. WALCOTT, DIRECTOR

THE GEOLOGY

EASTERN BERKSHIRE COUNTY

MASSACHUSETTS

BY

BENJAMIN KENDALL EMERSON

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1899

CONTENTS.

Page.

Introduction................................................................ 13

Topography ................................................................ 14

Historical sketch of the building of the plateau ......................... 17

Geology .................................................................... 18

Section of pre-Cambrian and Paleozoic rocks ............................ 18

Pre-Cambriau rocks..................................................... 19

Introduction........................................................ 19

Hinsdale anticline .................................................. 21

Hiusdale gneiss................................................. 22

Petrographical description .................................. 23

Hinsdale limestone.............................................. 27

Petrographical description.................................. 31

Lee gneiss ...................................................... 33,

Tyringhaui gneiss............................................... 34

Washington gneiss..............'................................ 34

Petrographical description; cause of blue color in quartz.... 37

Daltou anticline ..................................................... 39

Coles Brook limestone............................................... 41

Limestone on the Alderman farm in Becket.......................... 43

Gulf anticline, Dalton .............................................. 43

Lee-Tyringham area ................................................ 44

Distribution.................................................... 44

Boundary....................................................... 45

Structure....................................................... 45

Greenwater Pond anticline.................................. 45

East Lee anticline........................................... 45

Goose Pond anticline.... ..................................... 46

Foxden anticline............................................ 46

Hop Brook anticline .......................................... 46

General petrographical distinctions ............................. 47

Hinsdale gneiss............................................. 47

Hinsdale limestone ......................................... 47

Lee black gneiss ............................................ 48

Tyringharn ligniform, gneiss ................................. 49

Washington blue-quartz gneiss.............................. 49

Limestone areas................................................. 50

East Lee limestone.......................................... 50

Goose Pond limestone ................................... .... 51

Hop Brook limestone ........................ ................ 52

"Mortised rock" of Tyringhaui............................. 52

Metamorphosis of the pre-Cambrian limestone and paragenesis of limestone minerals.................................. 54

Sandisneld area..................................................... 55

Otis area ........................................................... 56

"Snowplow" anticline of Bear Mountain............................ 58

5
6 CONTENTS.

Geology Continued. Page. 

Pre-Cambrian rocks Continued.

Monterey area ...................................................... 60

Southern areas...................................................... 61

NewMarlboro area.............................................. 61

Area southeast of Southfield ..............................:..,.. 62

Harinon Pond area .............................................. 62

Southfield cemetery area........................................ 62

Hotchkiss area.......................................... ........ 62

Cleveland area.................................................. 63

North Canaan and West Norfolk areas............................ 65

Limestone ............................................ ...... 65

Nodular gneiss .............................................. 65

Campbell Falls section ...................................... 66

Nodules in the gneiss ....................................... 67

Southeastern area................................................... 68

Pyroxenites and amphibolites ....................................... 68

Analyses of pre-Cambrian limestones................................ 69

Cambrian system ....................................................... 69

Unconformity at the base of the Cambrian conglomerate............. 70

Conglomerate-gneiss ................................................ 71

Amphibolites in Becket gneiss .................................. 75

Cheshire quartzite ............................................ ...... 78

Kaolin from the quartzite ................................. ...... 79

Quartzite breccia ................................................... 80

Transition of limestone into sandstone .............................. 81

Silurian system ...............................................'...-...... 81

Hoosac schists ...................................................... 81

Windsor mica-schist bed ......................................... 81

Coltsville mica-schist bed ....................................... 82

Daltonbed ..................................................... 82

Mica-schist of Dry Hill in New Marlboro ........................ 82

Eastern baud ............................................. ...... 82

Eowe schist............................................. ............ 84

Stockbridge limestone .............................................. 84

Geology of Ferncliff Eidge, in Lee .............. .................. ...... 85

Cambrian quartzite................................................. 85

Lithology ................................................ ...... 86

Structure................................................. ...... 86

Silurian series ...................................................... 87

Lower limestone................................................ 87

Berkshire schist .'......................... ............ .......... 88

Silurian quartzite............................................... 88

Upper limestone ............................. .................... 88

Faults.......................................................... 88

Signification of northwestern thinning of Silurian quartzite...... 89

Faults.................................................................. 89

Hinsdale fault...................................................... 89

Dalton fault........................................................ 89

Artesian wells upon the Dalton fault............................ 90

South Dalton or Warner Mountain fault............................. 92

Lenox fault. ........................................................ 93

Tyringham fault.................................................... 94

Intrusive rocks ......................................................... 94

Pegmatite.......................................................... 94
CONTENTS. ' 7

 Continued. Page.

Glacial deposits......................................................... 95

Post-Glacial deposits.................................................... 95

Washington Basin .................................. ................ 95

Hinsdale lake........................................................ 96

Dalton kames...............~.................. ...................... 97

High terraces in Becket.................... ........................ 97

High sands at entrance to East Lee Valley .......................... 98

Deflected glacial drainage down the Hinsdale, East Lee, and Tyringham valleys....................................................... 98

Mineral resources........................................................... 98

Limestones............................................................." 98

Granite.....-..-- ....................................................... 99

Flagstones.............................................................. 100

Buhrstones ............................................................. 100

Glass sand.............................................................. 100

Road material.......................................................... 100

Soapstone .............................................................. 100

Iron ores ...................... ...... .......... ...... ...... ...... ....... 100

Graphite ............................................................... 101

Gold and coal............ ....................... ....................... 101

Mineral lexicon of eastern Berkshire County .... .... ....'.......... .......... 103

Albite........................................ .......................... 103

Allanite............................ .................................... 103

Amphibole.... ..............<............................,.............. 104

Apatite................................................................. 106

Aragonite .............................................................. 106

Barite.................................................................. 106

Beryl................................................................... 106

Biotite ................................................................. 106

Calcite ................................................................. 107

Chabasite .............................................................. 107

Chalcopyrite :........................................................... 107

Chondrodite............................................................ 108

Cliuochlore............................................................. 108

Cyanite................................................... .............. 108

Dolomite ............................................................... 108

Epidote ................................................................ 109

Fibrolite ............................................................... 109

Gadolinite.............................................................. liO

Galena ................................................................. 110

Garnet ................................................................. 110

Graphite.,.............................................................. 110

Hematite....... .......... .......... ........ .......... ................... Ill

Henlaudite............................................................. Ill

Ilmenite................................................................ Ill

Jefferisite............................................................... 112

Laumontite............................................................. 112

Limonite................................................................ 112

Magnetite ............................................................... 113

Melanterite............................................................. 113

Microcline.............................................................. 113

Muscovite .............................................................. 113

Natron ................................................................. 113

Oligoclase .............................................................. 114

Orthoclase............................................................. 114
8 -CONTENTS.

Mineral lexicon of eastern Berkshire County Continued. Page.

Opal...........................--...........:.......................-... 115

Phlogopite ............................................................. 115

Pyrite............ ....................................................... 115

Pyrolusite.............................................................. 115

Pyroxene............................................................... 115

Pyrrhotite .............................................................. 118

Quartz ........................................:........................ 118

Rutile.................................................................. 121

Scolecito ............................................................... 121

Serpentine.............................................................. 121

Spinel.................................................................. 122

Staurolite .............................................................. 122

Stilbite................................................................. 122

Sulphur .................... ............................................ 123

Talc................:..............-...............................--... 123

Titanite ................................................................ 124

Tourmaline..........'.....'.............................................. ' 125

Wernerite ................................................................ 1125

Zoisite ................................................................. 127

Bibliography ............................................................... 127

Index.......... .....I................... ..'................................... 136
ILLUSTRATIONS.

PLATE I. Figs. 1-5, sections of pre-Cambrian gneisses; fig. 6, oyanite changing

to muscovite.................................................... 26

II. Mortised rock; quartz pseadomorph after albite, containing cavities

of salite crystals; Tyringham................................... 52

III. Mortised rock; quartz pseudomorph after albite, showing twin 

striation and pearly luster, with cavities from which salite crystals have been removed; Tyringham ............................ 52

IV. Campbell Falls, New Marlboro; looking north......'............... ' 66

V. Norfolk railroad cut............................................... 76

VI. Hydes Falls....................................................... 84

VII. Geological map of Ferncliff and East Lee.......................... 86

VIII. Map of artesian wells on Dalton fault............................. 90

I.. Geological map of eastern half of the Housatonic quadrangle....... 102

FIG. 1. Sectionat iron bridge, Windsor..................................... 29

2. Steatite quarry near Windsor Falls ................................. 30

3. Section at lead mine east of Washington Station.................... 36

4. The Dalton anticline ............................................... 40

5. Section at Coles Brook on the Boston and Albany Eailroad.......... 41

6. The Coles Brook limestone, enlarged from fig. 5...................... 42

7. Hinsdale limestone at Alderman quarry............................. 43

8. Section of contact of Cambrian on pre-Cambrian east of Lenox

Furnace.......................................................... 44

9. Layer of Cambrian slate on vertical Lee gneiss ..................... 45

10. Overthrust of pre-Cambrian on Stockbridge limestone .............. 61

11. Limestone pinched into pre-Cambrian gneiss, Cleveland mine, New

Marlboro......................................................... 64

12. Overturned anticline in Cleveland Mountain, west of Harmon Pond,

New Marlboro.................................................... 65

13. Fault contact of pre-Cambrian on Cambrian, North Canaan .......... 65

14. Campbell Falls section (central part PI. IV), New Marlboro .:....... 66

15. Cambrian gneiss folding over pre-Cambrian limestone unconformably,

Middlefield ...................................................... 71

16. Amphibolite dike in Becket gneiss with pegmatite rim; quarry,

Becket........................................................... 75

'9

LETTER OF TRANSMITTAL.

AMHERST COLLEGE, 

Amherst, Mass., July 6,1898.

SIR : The accompanying work is presented for publication as a bulletin of the United States Geological Survey. It is supplementary to 

the text of the Housatonic folio of the Geologic Atlas of the United 

States, and should be used in connection with the maps and sections of 

the folio.

Very respectfully, your obedient servant,

B. K. EMERSON. 

Hon. CHARLES D. WALCOTT,

Director United States Geological Survey.

11

THE GEOLOGY OF EASTERN BERKSHIRE COUNTY,

MASSACHUSETTS.

By B. K. EMERSON.

INTRODUCTION.

The country here described is represented on the Becket and Sandisfield sheets, and in Bear 1 Mountain extends into the area of the Sheffield sheet, of the topographical map of the State of Massachusetts. 

On the east it adjoins the territory discussed by the author in a recent 

monograph of the United. States Geological.Survey.2 On the north it 

is bounded by the Hoosac Mountain area, which has formed the subject 

of a monograph by Professors Pnmpelly and Woltf.3 It is a section 

across the Green Mountain chain in Massachusetts, a deeply eroded 

region of pure Appalachian type, composed of sharply folded preCambrian and Paleozoic crystallines.

This territory forms part of a deeply trenched plateau, and along 

the western border of the area the ground sinks by a steep scarp to 

the low limestone valley of the Housatonic. Upon the upland the surface is underlain by a series of pre-Oambrian anticlines, more or less 

overturned to the west, which form an almost continuous band across 

the State. They are included in a much broader band of Cambrian 

conglomerate-gneisses. The Cambrian quartzite and the Stockbridge 

limestone rise somewhat onto the upland from the west, and the Cambrian gneisses dip steeply beneath newer sericite-schists along the east 

border of the area.

The axes of the folds strike mainly north and south, but in the 

western-central part of the tract they bend in great curves to the west, 

even into sickle shape, and in extreme form are overturned and at 

the same time bent in curves, producing a complex, fan-like structure.

1 The "United States Board on Geographic Names has decided that the name used for this mountain 

in the publications of the United States Government shall be Bear, and not Bearto,wn. The author 

of this bulletin states that there are other "Bear" mountains, and that this mountain will always be 

known in the region as Beartown Mountain. EDITOR.

2 The geology of Old Hampshire County, Massachusetts, by B. K. Emerson: Mon. TJ. S. Geol. Survey, 

Vol. XXIX.

3 The geology of the Green Mountains in Massachusetts, by K. Pumpelly, J. E. Wolff, T. Nelson 

Dale: Mon. TJ. S. Geol. Survey, Vol. XXHI.

13
14 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

TOPOGRAPHY.

The region under discussion preserves distinctly the form of a plateau. 

A most striking topographical feature of this plateau is its rapid 

sinking on the west to a limestone plain 1,000 feet above sea level. 

Where the limestone penetrates far east into the crystalline area, in 

Dalton, East Lee, and Tyringham, it is sunk to the same low level as 

in the open valley to the west, and that this is due to the solubility of 

the limestone is suggested by the fact that the Cheshire quartzite, 

much more exposed and softer, is preserved across the central part of 

Washington fully as far to the east and at a much higher level.

A low crest line runs N. 10° W. through Peru, in the northeast corner 

of the area considered, rising to 2,295 feet 2 miles south of the center of 

the town and continuing north as the crest line of Hoosac Mountain 

(Spruce Hill, 2,480 feet). From this crest line the plateau sinks slightly 

westward to where its bluffs look down on the Housatonic Valley, with 

the highest peaks rising from 1,740 feet in the northern part of the area 

to 2,075 feet in the central part.

In the southern half of the area the bluff which has formed the western edge of the plateau clear across the State extends westerly in Bear 

Mountain (1,865 feet), facing northward for several miles, and is then 

lower and less pronounced across the southern half of the area, sinking 

to 1,750 feet across New Marlboro.

Also in the southern half of the area another broad crest, replacing 

the first, rises on the west side of the plateau, reaches 2,120 feet in 

Becket Mountain, and broadens to the south across Tyringham and New 

Marlboro. These crests sink gradually toward the south. A broad but 

slight depression, occupied by many ponds, crosses the area between 

the crests, from Hinsdale to the Otis reservoir.

There is also a southeastward sinking of the level from the second 

crest line to 1,450 feet at the southeast corner of the area, so that the 

plateau dips west in its northern half and east in its southern half.

The watershed follows the first crest for several miles, then crosses 

the depression transversely to the west, and continues down the western 

crest. This throws most of the drainage into the Connecticut River, 

though the watershed makes a wide detour to the east around the headwaters of the Housatonic.

This watershed crosses three well-marked wind gaps or valleys, which 

are not occupied by any water course but from which tributaries of the 

Housatonic flow northwest and those of the Connecticut southeast. 

These are (1) the deep canyon between Washington Station and Becket, 

occupied by the Boston and Albany Eailroad; (2) the prolongation of the 

East Lee Valley at Green water Pond; and (3) the less marked upland 

prolongation of the low Tyringham Valley which connects with the Clam 

Eiver Valley. These wind gaps form the centers of the three important 

transverse features of the topography. The deep limestone bay of Dalton is continued in the pre-Cambrian basin of Hinsdale at a higher
EMERSON.] TOPOGRAPHY. 15

level, and this narrows into the Becket Canyon, which is continued in 

the Westfield River Valley across the whole range. Thus is formed 

the only passageway for a railroad across the range.

The Dalton limestone bay was caused by the removal of the Stockbridge limestone, which here penetrates far into the mountain mass. 

Bast of this bay the greater solubility and consequent erosion of the 

gneisses and limestones of the overturned pre-Cambriau anticline has 

caused the broad Hinsdale depression where the anticline is wide; 

and the same anticline narrows and becomes vertical where it bends 

southeastward, making the deep canyon which extends from Washington Station to North Becket.

The divide is now at Washington Station, and the Housatonic, coming down from the Washington Hills, flows north across the low depressions here mentioned and swings around to the south, following the 

larger limestone valley; the Westfield Eiver flows south through the 

canyon and then southeast until it joins the Connecticut.

From Becket eastward the position of the Westfleld is normal, 

depending on the original southeast slope of the plateau and disregarding the geological structure, except that it seems somewhat influenced by faults. Above this point the structure has controlled the 

course of the stream from Washington to Becket and forced it into 

the canyon; and the drainage also seems to have been inverted, that 

from Dalton, Windsor, and Hinsdale, which formerly went into the 

Westfield Eiver at Washington, being now carried westward by the 

Housatonic. If the course of the Housatonic from Dalton south be 

inverted, nearly all the tributaries on the west would then flow southeast in normal relation to it. A similar statement is true of several of 

those on the east in so far as they have not come under the influence 

of the limestone, which has by its solution produced long ponds and 

deflected several streams into them. Indeed, each lobe of the preCambrian has become the bed of a brook.

The present course of the Housatonic across Hinsdale is complicated 

by the extensive glacial lake deposits in that town. When the ice had 

just shrunk away from the uplands and still filled Pittsfield Valley 

and the Dalton bay, the valley of the Westfield became a main outlet 

for the glacial waters, which widened above Becket Canyon into a 

lake across the low ground of Hinsdale and Washington, producing 

the broad sand flats that extend across this area and the great delta 

flat which rises just east of Hinsdale station and extends to the Center. 

Its lobed southward-facing front, swinging in a great loop between 

these two places, is well marked on the map. The extremely sinuous 

course of the Housatonic is due to its passage, with slight fall, across 

these fine sands.

The notch across the mountains seen in the East Lee-Farmington 

Eiver Valley is formed in a similar way. The Stockbridge limestones 

project but little into the East Lee Valley of pre-Cambrian limestones, 

but this valley is prolonged into the Farmington Eiver Valley, which
16 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS, [BULL. 159.

cuts clear across the range. In its lower third, from New Boston south, 

the stream runs in a narrow gorge cut by itself without regard to the 

substructure and controlled by the old surface of the base-level plain 

over which it began its flow. The middle third is controlled in some 

degree by the Otis fault (see map, PL IX). The northwestern third is 

controlled similarly to the Hinsdale area, by the solution and erosion 

of the limestone and the formation of the deep East Lee Valley along 

the long and narrow anticline which sweeps in a broad curve from 

East Lee to West Becket.

South of the southern end of Green water Pond there is a low divide in 

the deep valley bottom. South of this point the waters flow into the 

Farmington Eiver; north of it they flow, by Greenwater Pond Brook, 

into the Housatonic. This brook seems also to indicate a reversed 

drainage, as the tributaries make obtuse angles with the main brook 

and seem to have once been tributary to a southeast stream.

The Dalton phase is lacking here, as the Stockbridge limestone does 

Dot peuetrate the crystallines.

The great Lenox fault at the foot of the mountains cuts across the 

mouth of the valley and gives access to it by dropping the western half 

of the Tyringham pre-Oambrian below the bottom of the Housatonic 

Valley.

In the Tyringham Valley, next south, the limestones once penetrated 

far southwest along the Tyringham fault, but have now- been mostly 

cleared out from the deep, narrow valley, which is abruptly closed at its 

lower end but continues at a much higher level to connect with the 

transverse valley of Clam Eiver, which joins the Farmington Eiver at 

New Boston.

One can dimly discern in the Tyringham Valley a fragment of preCainbrian topography and its explanation. In the Hop Brook gorge, 

at the head of the valley, the pre-Carnbrian limestones appear as the 

core of an anticline, which ends, with sharp southeastern pitch, near the 

mouth of Hayes Pond. This anticline extends. along the axis of the 

valley beneath the Cambrian and appears in its middle at the Brookside mill below the " Cobble," and its erosion in pre-Cambrian times 

can be said, with considerable probability, to have formed a long,-narrow bay, into which the progressive transgression of the Cambrian sea 

brought first the sand beds of Cambrian times and then the deepwater calcareous deposits which formed the Stockbridge marbles that 

once filled the valley. The steep southern pitch of the limestone core 

of the anticline at its south end caused the abrupt termination of the 

valley in that direction.

In a similar way a curious topographical feature was formed in the 

basin of Goose Pond. A long, narrow, curved anticline brought the 

limestone to a level where it could be reached by solution and erosion, 

and this deep linear depression is the result.

In Monterey the limestones extend again far eastward, and their 

solution has produced a broad upland valley and a westerly drainage
EMERSON.] HISTORICAL SKETCH OF PLATEAU. 17

whose limits are quite closely coincident with the former area of 

limestone.

Finally, in the southern portion of the area there are many small 

ponds occupying pre-Cambrian limestone areas and surrounded by 

Cambrian gneisses, where I suspect that the solution of the limestone 

lias caused the caving in of the gneisses, and that their final removal 

by the ice has produced these small and peculiar land-locked ponds.

HISTORICAL SKETCH OF THE BUILDING OF THE PLATEAU.

The country is now a central section of a deeply eroded mountain 

region of Appalachian type, sharply folded, and overturned northwesterly by forces acting from the east.

The pre-Cambrian rocks were folded and eroded no one knows how 

much in pre-Cambrian time, and toward the close of that time a deep 

north-south depression occupied the position of the present Housatonic Valley, extending far westwardly, and lateral valleys branched 

from it to the east up the present Tyringham, East Lee, and Dalton 

valleys.

The great transgression or passage of the waters across the region 

from the west, which introduced the Cambrian era, admitted water into 

this valley system, and as it advanced it deepened them so that limestones were formed in the valleys, while just east sandstones and conglomerates were laid down nearer the shore line, and there are many 

transitions from limestone to sandstone. The waters stretched west to 

the foot of the Adirondacks and continued east across Massachusetts, 

surrounding a large pre-Cambrian area which extends from the southeastern part of Worcester County across Connecticut to the mouth ot 

the Connecticut River, and reaching some large land body east of the 

present coast which furnished the material for the abundant conglomerates that appear in the Cambrian gneiss at Monson and in the 

Hudson arkose in Hudson and Marlboro and in Worcester County, and 

stretch far northeast into Maine, marking perhaps an old shore line 

near which the altered eruptives in the Marlboro region were extruded. 

 The continued sinking of the land, which sent the shore line so far 

east, beyond the region here studied, caused the conglomerates to 

change into sandstones, and these into shales which have now become 

the Eowe hydromica-schists and which are represented in Worcester 

County by the Paxton whetstone-schist.

Shales continued to be deposited in the east after the partial uprise 

of the Stockbridge limestone caused it to be covered by the shales which 

have become the Berkshire schists and which are continued east in 

the Goshen and Conway schists, and by the Brimfield schists east of 

the Connecticut. These may be about on the horizon of the Lower 

Trenton beds. 1

The increased folding brought nearly all this area above the level of 

the sea and produced the Bernardston Upper Devonian basin on the

1 The Washington limestone, by Dr. C. H. Richardson: Proc. Am. Assoc. Adv. Sci., 1898, p. 295.

Bull. 159 2
18 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

Connecticut, and the Worcester late Devonian or Carboniferous basin, 

both apparently opening toward the north.

For the later movement of folding and crushing, the New York horizontal Paleozoic country is the unfolded "foreland" toward which the 

folds advanced; the "rearland," or country from which the pressure 

came, has sunk into the Atlantic off the present east coast; the great 

bands of granite which cross the middle of the State are the eruptives 

on the concavity of the folded ranges melting up in the great synclines. 

Here, in the core of the range and a long way west across the foreland, 

eruptives of the time of the folding are wanting.

The Connecticut and Housatonic valleys are "graben," 1 or long narrow areas sunk between faults. These faults bound the intermediate 

block or "horst" which forms the Green Mountain upland. It is simpler to assign them both to the same pre-Triassic era.

Erosion has since worn the mountain range down to its roots, and 

the "Cretaceous base-level" thus formed may have extended, with some 

approach to horizontality, across the area and westward, touching the 

crests of the Taconics and of Greylock and Mount Washington, to the 

north and south, respectively. If this be true, all the later irregularities would depend upon the unequal capacity for erosion of the two 

areas, especially upon the solubility of the limestone. The alternative 

would be that the great depression of the Housatouic limestone valley 

was in some large part caused by the later downthrow of the limestone 

area between faults already established. The former supposition seems 

to me more probable. It would place the downthrow wholly before the 

Cretaceous base-leveling.

GEOLOGY.

I have distinguished the following subdivisions of the pre-Cambrian 

and Paleozoic rocks in the Becket and Sandisfield quadrangles, which 

are described in this paper.

SECTION OF PRE-CAMBRIAN AND PALEOZOIC HOCKS IN WESTERN

MASSACHUSETTS.

SILURIAN.

West of the pre-Cambrian.

BERKSHIRE SCHIST.

Ckloritic hydromica- or sericite-schist.

STOCKBUIDGK LIMESTONE (upper part).

A white sugary marble, ofteii tremolitic, with included schist and qnart/ite 

beds.

Mast of the pre-Cambrian.

KOWK SCHIST.

Light greenish gray sericite-schiet, 

grading southwardly into a feldspathic 

mica-schist.

HOOSAC SCHIST.

Dark-gray albitic sericite- (hydromica-)

schists.

1 Suess, Das Antlitz der Erde.
EMERSON.] PRE-CAMBRIAN ROCKS. 19

CAMBRIAN.

East of thepre- Cambrian. 

BECKET GNEISS.

A light-gray friable gneiss, often granitoid.

West of the pre-Cambrian,

STOCKBRIDGE LIMESTONE (lower part). 

CHESHIRE QUARTZITE.

White sugary'quartzite, often tourmaline bearing.

BECKET GNEISS.

A light-gray, fine-grained, two-mica- or 

biotite-gneiss, often conglomeratic, with 

subordinate beds of quartzite and schist.

PRE-CAMBRIAN.

WASHINGTON GNEISS.

Rusty, graphitic, and garnetiferous blue-quart^ 'gneiss, becoming fibrolitic toward 

the south.

TYRINGHAM GNEISS.

Coarse, highly stretched biotite-gneiss, barren of accessories.

*.*

LEE GNEISS.

A perfectly banded, medium, black, hornblendic gneiss, sometimes alternating 

with a white, fine-grained, often micaless, gneiss.

HINSDALE LIMESTONE.

Coarse, highly crystalline, chondroditic limestone.

HINSDALE GNEISS.

Coarse, granitoid biqtite-gneiss, often epidotic.

PRE-CAMBRIAN ROCKS. 

INTRODUCTION.

A long series of isolated outcrops of pre-Cambrian rocks occupies 

the western riin of the high ground which extends from north to south 

across the eastern portion of Berkshire County and looks down on the 

limestone valley of the Housatonic. They form the axis of the Green 

Mountains across Massachusetts. (See map, PI. IX.)

The most northerly outcrops of the pre-Cambrian within the limits ofthe State are the area of Stamford gneiss of Oak Hill, north of North 

Adams, and that stretching along the crest of the Hoosac Eauge south 

of the tunnel. These have been described in detail by Professors Pumpelly and Wolflf, and their relations to the inclosing Cambrian gneiss 

have been elucidated in a work which marks an epoch in the investigation of the crystalline rocks of New England. 1

The Hoosac area is described as consisting of " a coarse granitoid 

gneiss which forms the core of Hoosac Mountain proper, occupying the

1 The geology of the Green Mountains in Massachusetts, by K. Pumpelly, J. E. Wolff, and T. Nelson 

Dale: Mon.TJ.S.Geol.Survey,Vol.XXHI.
20 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS.. [BULL. 159.

surface of the mountain for several miles, then disappearing below the 

overlying rock, but cut in the Hoosac tunnel for nearly 5,000 feet." It 

is called the Stamford gneiss. It is u a coarse-banded gneiss, composed 

of long lenticular crystals of pinkish feldspar, flattened lenses of blue 

quartz, and thin, irregular, greenish layers of a micaceous element 

(biotite or muscovite, or both) mixed with small epidote crystals." 1 It 

varies but slightly in microscopic and macroscopic characteristics, and 

Professor Wolff does not attempt to subdivide it in the- field or to 

decide whether it is an eruptive granite or a highly metamorphosed 

member of a detrital series.2 Specimens have been taken from the 

material of this age brought to the surface in the central shaft of the 

Hoosac tunnel to illustrate pre-Cambrian gneissoid granite in the educational series of rocks distributed by the United States Geological 

Survey.

All the other outcrops of the series are described in this bulletin, 

beginning with the Hinsdale area in the Becket quadrangle, which is 

traversed by the north and south portion of the Boston and Albany 

Railroad, and extending south across that and the Sandisfield quadrangle. The series continues southwest across Connecticut and New 

York to the Highlands. Several of these areas extend a little way 

over into the Sheffield quadrangle on the west, and Professor Hobbs 

thinks that the Cambrian gneisses are worn through, exposing small 

areas of the pre-Cambrian, on Warner Mountain in Great Barrington 

and on Brush Hill in Sheffield. The Canaan Mountain pre-Cambrian 

enters the Sheffield quadrangle, but not the State of Massachusetts. 

There are thus twenty-three pre-Cambrian areas in the western part 

of the State.

These areas change progressively as they cross the State. The 

Hoosac Mountain area is a monotonous mass of coarse porphyritic, 

granitoid gneiss of doubtful, but probably eruptive, origin.

The Hinsdale area is a closely appressed and slightly overturned 

anticline, exposing a nucleus of ancient epidotic gneiss surrounded by 

a thick bed of highly crystalline, chondrodite-limestone, and this by a 

band of dark gneisses, while the series is closed by a rusty graphitic 

blue-quartz gneiss. The whole is in apparent conformity, and no striking unconformity marks its contact with the surrounding Cambrian 

gneisses. On the west of this anticline the blue-quartz gneiss alone is 

exposed in the Dalton anticline as the core of a normal fold, in sharpest unconformity to the Cambrian conglomerate.

Widely separated on the east, the Coles Brook limestone baud is 

thrust up irregularly through the Cambrian gneisses. It is extremely 

long and narrow, and the dark East Lee gneiss accompanies it at its 

southern end.

To the south of these the broad Tyringham area shows extensive 

bands of a barren and monotonous coarse biotite-gneiss (the Tyring1 Loo. cit., p. 45. 2 Loo. cit., pp. 47,48.
BMHRsoN.1 HINSDALE ANTICLINE. 21

liain gneiss) characterized by such extreme stretching that the biotite 

masses are drawn out into long pencils, and foliation surfaces of the 

rock appear as if lingers had been dipped in ink and drawn across 

them. This is bordered by the Washington blue-quartz gneiss, the 

upper member of the series, and strips of this rusty blue-quartz rock 

are infolded as synclines in it, while the East Lee dark-banded gneiss 

appears as anticlines. When the latter is worn through, the limestone, or the pyroxene-wernerite or actinolite rock which represents it, 

appears. In the northern part of the Tyringham area the pre-Cambrian 

is in apparent conformity with the Cambrian gneisses above, but in the 

southern part it is in plain unconformity with them. In the latitude of 

Otis village the blue-quartz gneiss begins to be fibrolitic, and this character becomes more and more pronounced toward the south. The 

broad Sandisfield area is a low dome which scarcely exposes anything 

except the Washington gneiss there a rusty fibrolite-gueiss rarely 

showing blue quartz and allanite, which extends into Connecticut and 

carries small beds of choudrodite-limestone.

Finally, in the small areas to the southwest, which are exposed by 

the solution of the limestone and the sinking and removal of the 

Cambrian gneisses, the rock is still more strongly ferruginous than 

farther north, and much magnetite, pyrite, and pyrrhotite appear.

From Campbell Falls south long bands of a dark schistose biotitegueiss occur, which are full of rounded nodules of microcline largely 

changed to inuscovite and full of fibrolite. The same occur, in the 

southern part of the Sandisfield band.

This change in the character and arrangement of the pre-Cambrian 

rocks has had a marked influence upon the topography of the range 

throughout its course across the State of Massachusetts.

In the solid block of the Stamford gneiss the pre-Cambrian composes 

the crest of the mountain range, while farther south its limestones 

have by their solution formed all the passes across the mountains and 

many rock-bordered ponds.

HINSDALE ANTICLINE.

A large portion of the towns of Hinsdale and Washington is occupied by this area of pre-Cambrian rocks, which form an anticline closely 

appressed and slightly overturned to the west. It is 12 miles long and 

4 miles wide. For the greater portion of its length its axis is north 

and south, but it narrows at its southern end and bends southeastward 

in sympathy with the Tyringham anticline, ending in the river bed a 

mile below North Becket station. It also sends an irregular fold southwestward past Washington Center. To the north it ends in several 

lobes projected far into the town of Windsor.

The east-west fault which limits the Dalton anticline on the south 

extends far into the center of this anticline and nearly bisects it. As 

a result, it is much more sharply folded to the south of this fault,
22 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BOLL. 159.

forming a compensation for the fold of the Dalton anticline, which is 

only partly continued in a slight fold south of the east-west fault.

The Hiusdale anticline is taken as the type of the pre:Cambrian 

areas, since it is the only one which exposes a gneiss older than the 

Hinsdale limestone and the one which shows the pre-Cambrian rock 

series in the fullest way. For this reason the names of the different 

subdivisions have been mainly drawn from this tract.

HINSDALE GNEISS.

This rock emerges from-beneath the Hinsdale limestone and lies in 

the bottom of the Hinsdale Basin. The upper pre-Cambrian gneisses 

and, in an even more marked way, the Cambrian gneisses form an 

unbroken line of high hills around it on every side.

The great area of deeply rotted rock which surrounds the Washington 

station and which was sheltered from the erosive action of the ice 

suggests that the whole basin was deeply decomposed at the beginning 

of the Glacial period and was thus in part excavated by the ice.

The only place where it can be studied in considerable outcrops is on 

both sides of the roads forming a square a mile north of Hinsdale 

Center. The commonest rock along the western road of the square is 

a light-colored, well and coarsely bedded, epidote-biotite-gneiss (see 

detailed description, page 23, and fig. 1 of PI. I, p. 26). The large, 

curved-faced feldspars are mostly crushed to a granular mass, and the 

result is a rock somewhat like the white Cambrian gneiss, but much 

firmer and coarser and often showing muscovite of secondary origin 

on the foliation faces. Other beds are compact and massive and show 

some blue quartz, which is rare in the Hinsdale gneiss.

Farther north along this road the rock is a coarse granitoid feldsparquartz mass, rudely foliated fey distant biotite-epidote films, and in 

places strongly stretched. Eocks of this type extend north into a 

great double-topped hill and make up its western crest.

A peculiar altered limestone bed about a rod thick can be followed 

from north to south along the top of this western crest. It is mostly 

changed to silicates, among which tremolite in coarse blades forms 

beautiful cabinet specimens, and a green clinochlore in coarse plates is 

very abundant. It is in places broken up into a series of great lenses 

which run along the strike. This is plainly a result of the solution 

of part of the limestone and the compression of the gneiss around the 

remnants. One of these lenses is a mass of hornblende-pyroxeneepidote-calcite rock with eozob'n structure.

This limestone appears north of the road running southeast from the 

center of Hinsdale, near the creamery. The rock is a rusty thin-bedded 

gneiss, with traces of a layer of limestone, now almost wholly changed 

to a coarse salite-actinolite-graphite-calcite rock. A shaft was sunk 16 

feet deep on this rock in 1885, in search of graphite, and later, in 1895,
KMBBSOK.] HINSDALE ANTICLINE. 23

more digging was done at the same spot in search of iron. The adjacent rock is exceptional on this horizon, and resembles the Washington 

gneiss which surrounds the basin as the newest member of the preCambrian series. It lies in the middle of the anticline.

On the eastern road of the square, layers of very dark gneiss carrying 

much biotite and hornblende alternate many times with the common 

gray biotite-gneiss and are shot through by small pegmatite veins.

This structure is very characteristic across the eastern peak of the 

double hill already mentioned. Bands of the two rocks only 3 to 10 

inches thick and preserving their widths for long distances, alternate 

regularly, and the lighter rock weathers more easily into deep grooves, 

bringing out strongly the continuous strike or in places the great contortions of the bed. This bed can be followed south about 2 miles.

The most interesting type of the Hinsdale gneiss and the most 

accessible outcrops are 50 rods north of Hinsdale station, on the west 

side of the railroad. The gneiss rests directly upon the limestone, the 

rocks being there overturned, and dips 35° SE. It is a peculiar, fresh, 

coarse gneiss of very white color, although it contains a jet-black biotite 

in considerable quantity. (See detailed description below.)

These rocks seem characteristic of the horizon just under the limestone, and there is a similar curious rock developed on a similar horizon 

at the northwest corner of the square of roads mentioned above. It is 

a coarse flesh-colored gneiss made up almost wholly of feldspar, with a 

foliated structure imparted by widely separated streaks and flat 

blotches, all stretched in a common direction and containing a darkgreen fibrous hornblende, epidote, and dark-brown titanite.

Structure. There is a marked prevalence of northerly strikes and 

moderate easterly dips in the structure places of the coarse gneisses, 

and when separate beds can be traced they take the same direction. 

This agrees with the posture of the limestone bed which surrounds the 

Hinsdale gneiss.

If the limestone bed at the creamery is an integral part of the series, 

it is not improbable that the whole may be of sedimentary origin. It 

makes, however, the impression of a very coarse and not greatly 

altered granite.

PETEOGBAPHICAL DESCRIPTION.

Biotite-microcline-gneiss. Fifty rods north of the railroad station at 

Hinsdale is a coarse, white, biotite-epidote-microcline-gneiss of granular texture. In its lower layers the fresh black biotite is in widely 

separated films mingled with epidote grains. In its upper layers the 

biotite is aggregated into flattened lenticular biotite-epidote masses, 

placed an inch apart in the foliation planes. The mass of the rock is a 

dull white mixture of much feldspar and a little pale bluish quartz. It 

contains pyrite in small pentagonal dodecahedrons and submicroscopic 

zircons of a dark clove-brown color. The feldspar which forms nearly 

the whole mass of the rock is uniformly microcline in large cleavage
24 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. FBULL. 159.

pieces, which are granulated at the border and included in broad patches 

of the granulation mosaic. The remaining fragments are strongly and 

regularly curved in the cleavage faces, but show no trace of the intergrowth of albitic bands. Sections parallel to OP (001) show with 

the lens small, rounded, opaque spots, which on examination prove 

to be bodies placed in the intersection of the two twinning systems. 

They are cylindrical, with rounded ends, and seem to be muscovite crystals elongated parallel to the c axis and slightly twisted; often a slight, 

lateral pressure has changed them into a pile of overlapping scales. 

An immense number of epidote grains, small crystals, and microlites, 

and many minute-lobed plates of biotite are evenly distributed. This 

multitude of inclusions causes the opaque-white look, but there does 

not seem to be any trace of kaoliuization or weathering. It is epidotization due to metamorphism proper.

The feldspar has the complete microcline structure and pronounced 

prismatic cleavage, and large patches are still untwinned microcline.

The quartz contains a few short, straight, black microlites unlike the 

long rutile trichites of the granites. The trains of cavities are very 

abundant, and often run through several grains of quartz, suggesting 

crushing. They are made up of very small cavities with motionless 

bubbles unaffected by heat.

Biotite-gneiss and granulite. Following the railroad a few rods north 

from the outcrop of the white gneiss described above, one finds in the 

wall of the railroad cut an outcrop of a dark-gray, stretched, granitoid 

gneiss of more normal texture and somewhat finer grain than that last 

described, which abounds in minute garnets, so that as the mica disappears from some layers they become a light-colored granulite.

Under the microscope it is very unlike the former rock. Microcline is 

almost wanting, and the mass of the rock is a quartz mosaic of irregular grain, with little microcline and orthoclase, with very wavy extinction, and with a triclinic feldspar near albite. The dark olive biotite 

is raveled out at the edges and changed to chlorite. The small, round, 

red-brown garnet grains are generally without inclusion and are nonpolarizing. The only remarkable peculiarity of the rock is that large 

grains of quartz and plagioclase have their centers full of blebs of garnet, quartz, and biotite, while there is entire freedom from nodules or 

water bubbles. There is every sign of rapid crystallization.

JEpidote-gneiss. Next above the preceding rock is a coarser gneiss, in 

which greenish layers of biotite, mixed with much green epidote and 

secondary chlorite in broad, distinct sheets, inclose a fine granular 

mosaic.

In sections cut across the foliation the microscope shows this mosaic 

to be made up of elongate-opaque patches, with intervening transparent 

portions. The latter are a quartz mosaic; the former are portions of a 

feldspar so filled with minute pale-green epidote that the character of 

the feldspar can not be determined. The frequency of crushing is
PLATE I.

25
PLATE I.

FIG. 1. Hinsdale gneiss, from near N. B. Whitman's house, in the northern part of 

Hinsdale. The lighter quartz bands are drawn with polarized light to obtain the 

boundaries of the grains in the mosaic. The darker bands of plagioclase are drawn 

with common light to obtain a clear view of the minute epidote, biotite, and chlorite 

crystals. X 14.

FIG. 2. Washington gneiss, Peru; H. A. Messinger farm. (Slide F.). The granular bands represent a fine quartz-feldspar mosaic, in which much newly formed 

muscovite is regularly disseminated in fine scales. The intervening bands are of 

limpid quartz, which is little fissured. The slide is drawn with polarized light and 

the strong undulose extinction of the quartz bands is represented by shading, x 14.

FIG. 3. Washington gneiss, Washington, north line of Pittsfield road. Three 

bands of a quartz-feldspar-muscovite mosaic (F) and a central biotite-inuscovite 

band (B) are separated by three bands of blue quartz (Q) in the dotted portion of 

which (Q') the blue color has been discharged. A well-defined rhombohedral cleavage appears in part of the quartz, x 3, natural light.

FIG. 4. A portion of the lower part of the upper-quartz baud of Jig. 3. The 

dotted portions (Q/) do not show the blue color, but are not otherwise distinguishable,'and the cleavage lines run through both portions. X 14, natural light.

FIG. 5. The above slide (fig. 4) seen with polarized light, showing the coincidence 

of the crushed and colorless portions (Q') and of the parts with undulose extinction 

and those with the blue color (Q). The cleavage lines make an angle of 74° instead 

of 94°, and the oblique position of the axial cross agrees with this decrease of the 

cleavage angle.

FIG. 6. Cyanite (K) changing to muscovite (M) with included garnets (G). 

Becket, p. 84. 

26
U. S. GEOLOGICAL SURVE ULLETIN NO. 159 PL.

THIN SECTIONS OF GNEISSES AND CYANITE.
EMKHSON.] HINSDALE ANTICLINE. 27

/>

shown by the sheets of cavities passing through the quartz grains. 

These cavities rarely show bubbles, and only the smaller show motion, 

When heated to 70° 0. they are not changed.

Blue-quartz gneiss. At N. B. Whitman's house, in the north part of 

Hinsdale, is a granitoid gneiss (PI. I, tig. 1) in which the small distant 

aggregates of black biotite and epidote do not much aid the foliation. 

Pyrite is abundant. Bands of blue quartz, about 1 to 3 millimeters 

wide and about twice that distance apart, run interruptedly through 

the rock; they have crushed borders or dissolve entirely into a white 

mosaic. Between these is an opaque white mosaic of feldspar crowded 

full of minute epidotes.

The quartz mosaic represented in the figure by the two broad light 

bands is very fresh. Sheets of minute pores or solid particles pass 

from grain to grain. Many of the grains have a delicate wavy extinction. The feldspar, which crosses the figure in three bands, is much 

coarser, and the feldspars are uniformly a plagioclase with extinction 2 

degrees to 12 degrees, generally very low, indicating an acid plagioclase. It is very fresh, and the small sharp epidote, biotite, and chlorite 

crystals are spread evenly over the field, like the small crystals in a 

micro chemical experiment, giving the band a glistening, satiny look in 

the thin section. There is no indication of decomposition, but rather 

of an original formation of the feldspar mass made up of large allotriomorphic grains, a fissuring of it, a subsequent formation of blue 

quartz in the fissures, and a later inylonitic effect upon the whole. It 

is interesting that there is here no trace of microcliue or orthoclase, 

but that the abundant growth of the small, sharp epidote, biotite, and 

chlorite crystals appears equally well in the plagioclastic as in the 

microcline-bearing rock, and seems in both to be a result of intercrystallization rather than a secondary alteration of the feldspar.

HINSDALE LIMESTONE.

In the more regular portion of the syncline across Hinsdale so many 

outcrops of the rock have been found that it is quite certain that a 

heavy band of limestone, often changed in whole or in part to amphibolite, steatite, or serpentine, encircles or did once encircle the lowest 

gneisses. It is marked by a series of abandoned limekilns, and before 

the opening of the " Western Railroad " was of economic value. Several 

of its outcrops were mentioned by President Hitchcock, and Professor 

Dana 1 called attention to the locality at Hinsdale Station as containing 

cliondrodite, and from this fact assigned these rocks to the Archean 

that is, to the pre-Cambrian.

As exposed in the railroad 50 rods north of the Hinsdale station the 

limestone is a very coarse, wholly crystalline rock a white coccolitelimestone containing graphite, chondrodite, phlogopite, and coccolite

i Am. Jour. Sci., Vol. XXXIII, 1887, p. 275.
28 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BOLL. 159.

in grains, and hornblende in larger masses, some of which are a foot 

across. Only 25 feet is exposed, and it is covered by the coarse Hinsdale 

biotite-gneiss. A mile south, where the highway crosses the railroad 

near a bridge, the bed reappears and continues for a long distance southward by the roadside, more than 100 feet in thickness being exposed. 

It is here a very coarse crystalline limestone, the grains often 50 to 100 

mm. across and multiple twinned, with crystals of bronzy and pink 

phlogopite 20 to 30 mm. across, and black to pale-green hornblende, 

clove-brown pyroxene, green coccolite, graphite, and pyrite. It is in 

places changed into great masses of matted pale-green tremolite. and 

this can be followed a long way southward as a very impure tremolitic 

limestone. It appears as a phlogopite-limestone farther south, at the 

E. Cheesman place, a half mile west of the next railroad crossing. From 

this point the bed is covered for a long way south, and I have located 

it approximately on the map by fixing the boundary between the coarse 

Hinsdale gneisses and the upper rusty gneisses and also by the fact that 

its course is marked by abandoned limekilns and ponds and swampy 

areas where it has been deeply dissolved. In the second cut south of 

the Hinsdale station are great bowlders of serpentine which came from 

some portion of the bed.

Just east of Muddy Pond, north of Washington Station, the band is 

represented by the old graphite mine of Washington (see fig. 3, p, 36), 

which reminds one, except for the size of some constituents, of the 

graphite vein at Ticonderoga. It contains very coarse calcite, graphite 

in broad hexagonal plates, coarse white salite, coarse green pyroxene 

and hornblende masses, groups of finely terminated pistachio-green 

pyroxene, brown sphene, pericline, adularia, and garnets, followed paragenetically by coarse calcite with phlogopite, and this by quartz. This 

has been opened 6 rods along the strike and a shaft sunk 25 feet.

A hundred yards of a fine-grained compact gneiss containing much 

ilmenite, which I associate with the older gneiss, separates this deposit 

from a thin bed of limestone on the east; these two beds can be traced 

south, and cross the road, beneath the two most easterly houses on it, 

as two beds of amphibolite. South of the pond the outcrops are good, 

and but a single bed of a pyroxene-hornblende rock can be found as 

the representative of the united beds, and this swells and contracts in 

a series of great bunches, due to the removal of most of the limestone 

by solution.

A remarkable outcrop occurs in the eastern band, 50 rods west of the 

house of O. Bills and 150 rods east of the southernmost railroad crossing in Hinsdale. Here great layers 3 feet thick are made up almost 

exclusively of red chondrodite and bright green clinochlore, the latter 

in plates up to an inch across, and the change into serpentine and talc 

has taken place on a large scale.

Farther north, at Eiver Bend Farm, below the mill pond on the 

Housatonic branch, the limestone is exposed at the sawmill with a
EMERSON.] HINSDALE LIMESTONE. 29

thickness of 600 feet and the base is not seen. At top the bed is 

changed into a compact, firm, granular, apple-green talc for a thickness 

of 50 feet, and dark-gray slaty serpentine appears here also in bowlders. 

It is divided by a narrow band of gneiss. The limestone is marked by 

distant partings of phlogopite and much of it is a fine white marble, 

faintly banded by dark interrupted streaks. Other extensive outcrops 

occur farther north, but add nothing to the petrographical characteristic of the rock.

The bed can be traced up to the southern end of the Ashmere reservoir, and the long, deep depression occupied by this pond may be taken 

as its continuation, and the ruins of an old kiln may be found just 

beyond the north end of the pond, on a rusty calcite-garnet-hornblende 

rock.

A mile and a half north, on the northern branch of the Housatonic, 

is E. Cady's lime pit. Extensive excavations have been made in a bed

FIG. 1. Section at iron bridge, Windsor. LG-, Lee gneiss; HL, Hinsdale limestone; HG, Hinadale

of coarse limestone which has strike, N. 20° E., dip, 45° E. at its south 

end, and strike, N. 10° W., dip, 65° E. at the north end, where the bed 

is 83 feet thick, including one rod of coarse hornblende-gneiss. The 

limestone contains much hornblende and phlogopite. One layer of a 

dark amphibolite is two inches thick with the bedding.

A most interesting outcrop occurs farther north on the HinsdaleWindsor road at the iron bridge. This is at the apex of the northeastern lobe of the limestone. (Fig. 1.) A sharp fold of the overlying 

gneisses exposes the limestone in a narrow band which runs up from 

the last locality, and whose apex is exposed here on the bank of the 

brook. The older gneiss upon which the limestone rests appears beneath 

the latter at the level of the brook and the newer gneiss (the dark Lee 

gneiss) arches with many faults over the coarse white limestone, and 

it is very clear that there has been much solution of the latter and 

adjustment during the folding of the rocks. The Lee gneiss is a white 

crushed gneiss with large blotches of hornblende and allanite. The
30 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

allanite is especially abundant beneath the bridge, and the hornblendic 

rock appears as a thick bed of a massive black, heavy, white-spotted 

gneiss in the fine cliff across the road to the west.

To the west of this outcrop is the high hill of black, crumpled, 

fine-grained mica-schist (phyllite). The lobe of pre-Cambrian rocks 

which runs up the east side of this hill is matched by a similar lobe 

running up the west side, and the curved reservoir pond seems to lie in 

the continuation of the limestone.

The dam at the outlet of the pond is a wavy bed of dark-green 

amphibolite, which still contains a central band, 1 to 5 feet thick, of 

coarse crystalline limestone.

A little farther down the brook, and easily reached by a footpath from 

the Windsor or Wakonah Falls, is an extensive bed of steatite. Here 

the limestone bed has changed through actinolite into steatite (fig. 2), 

and the influence of the removal of the limestone is clear. The steatite 

has been worked out of great chambers, the back walls of which are 

composed chiefly of gneiss. The gneiss layers can be seen to be

Fia. 2. Steatite quarry near Windsor Falls, Hinsdale. Gneiss folding round a bed of steatite.

very complexly corrugated in the immediate vicinity of the steatite, 

and at the left of the figure they bend at right angles and run, with 

many corrugations, down the whole end of the steatite bed, cutting it 

off completely. The strike here is K. 30° E. with the plane of the figure, 

and the dip is 50° Ev or from the observer. The gneiss is the white andblack banded Lee gneiss. Its position plainly indicates that it has 

been crushed in around the remnant of the limestone bed spared from 

solution and sharply faulted.

Upon following the limestone S. 30° W. a half mile, to the point where 

it runs into Dalton and crosses the east-and-west road south of P. Mitchel's, it is seen that the boundary line soon begins to be marked by a great 

number of serpentine bowlders. Thirty rods north of the residence of 

D. J. Pratt a great bed of serpentine 3£ rods wide has been quarried and 

is exposed. It is very dolomitic and slaty; much of it is still matted 

tremolite and actinolite. It sometimes shows a rich nickel-green color, 

but is much fissured and worthless.

From this point the limestone bed is concealed, and I have followed
BMBBSON.] HINSDALE LIMESTONE. 31

it, by bowlders and by the strike of the adjacent rocks, for a long distance southeast. It occupies and its removal has, I think, caused 

the deep depression at the north and east foot of the high, rocky hill a 

mile north by east from Hinsdale Center.

The bed appears beside the western road of the square mentioned in 

describing the gneiss, 1 in a deep excavation several rods long, with an 

exposed thickness of 20 feet. The black Lee gneiss is in place just 

west, and to the east is the peculiar titanite gneiss mentioned on page 

23. The limestone is a very pure white, coarse crystalline rock, with 

small bright coccolite grains and much shining black mica. It is 

peculiar that this mica is arranged in long streaks and blotches in distant plaues and exactly simulating the white, stretched gneiss which 

occurs so commonly just below the limestone.

It is not until we reach the blind road which runs up onto the hill 

from near the cemetery at the center of Hinsdale that we again come 

to ledges showing traces of the limestone band; but the Lee gneiss, 

which is its constant associate, can be followed almost continuously in 

the high ground of the hill. In the head of the brook bed east of the 

second house on this road appear great bowlders, apparently almost in 

place, of an actinolite-limestone which fixes the position of the bed.

PETROGRAPHICAL DESCRIPTION.

Chondrodite-limestone. At Hinsdale, north of the railroad station, is a 

limestone which ranges in color from white to pink, a rather coarse 

(grains 3-5 mm.), highly crystalline rock, with a certain translucency 

in the grains which immediately distinguishes it from all the other 

limestones of western Massachusetts and allies it to the limestones of 

the Adirondacks.

It carries coccolite, phlogopite, biotite, actinolite, chondrodite, 

pyrite, and magnetite. Generally the coccolite or the chondrodite, or 

both, are so abundantly and evenly scattered through the mass that it 

deserves the name coccolite-limestone or chondrodite-limestone, and 

the accessory minerals are so arranged as to give the mass a distinct 

foliation, especially where the chondrodite and biotite predominate.

The chondrodite is disseminated through the rock in yellow patches, 

elongate and parallel to each other, and as in places it changes into 

black patches, by the admixture of a green mica and magnetite, the 

resemblance to the boltonite from Bolton, Massachusetts, is striking, 

especially in specimens of the latter which are changing to serpentine. In large masses it is a rich deep red, like the chondrodite from 

the Tilly Foster mine. Under the microscope the patches of the mineral are seen to be composed of crystalline grains, fresh and free from 

inclusions and wrapped around by scales of a pale-green micaceous 

mineral, without any indication that the one mineral has been derived 

from the other. The mineral shows strong dichroism, honey-yellow to

1 Lat. 42° 28'; loug. 73° 6'.
32 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

deep red-brown. Toward the surface of the ledge the choudrodite 

weathers to a honey-yellow, opaque, serpentinous mass.

The phlogopite is in small, thick crystals with rounded borders, and 

has exactly the same bronzy color as the phlogopite from Teuipleton, 

Canada. Its crystals are generally surrounded by a band of scales of 

greenish-gray biotite. Both minerals are fresh, and there is no indication of a transition of one into the other. It has often a beautiful peach - 

blossom color.

The biotite is often in black scales, at times in isolated crystals with 

rounded contours, at times bordering the phlogopite in greenish-gray 

matted scales.

The pyroxene occurs in dark-green grains of coccolite scattered 

through the limestone, and in small, stout, limpid, emerald-green prisms 

in the pink variety of the rock.

The-magnetite occurs in small crystals and crystalline grains, often 

associated with thechondrodite; the pyrite is always in small complex 

crystals.

An analysis of a specimen of this limestone, made in the laboratory 

of Amherst College by Mr. F. H. Fitts, is here given:

Analysis of chondrodite-limestone from Hinsdale Station.

CaO-. ..............................................................

MgO....... ........................................................

FeO................................................................

CO.................................................................

Total........................................................

Per cent.

21.96

41.31

1.87

.68

34 71

100. 53

Actinolite-limestone. Forty rods north of Hinsdale station, in the 

canal beside the stone mill, there is a green massive rock of medium 

grain, showing a paler green massive pyroxene, a darker green fibrous 

hornblende, and much pyrite.

With the lens the slide shows little chlorite and much epidote, and 

in a few places the colorless ground appears. Under the microscope this 

colorless ground proves to be a much-twinned calcite, into which the 

terminations of the epidote crystals project. Large colorless areas of 

pyroxene are intergrown with the hornblendic mineral, which varies 

in appearance from actinolite to tremolite.

In the Massachusetts survey collection No. XV, 168, is a vein or layer 

of siliceous calc.ite in gneiss, labeled "Augitic gneiss, Washington, 

NW. part." It contains a dark-green fibrous hornblende in large 

blades, derived apparently from a light-green pyroxene which exists 

in remnants, and also from crystals of a dark-brown titanite.
EMERSON.] PRE-CAMBRIAN ROCKS. 33

T,EE GNEISS.

The type of the Lee gneiss is found in the hill overlooking East Lee 

on the northeast, where the rock is a heavy-bedded black gneiss. It is 

often a flat-banded black gneiss, alternating in thin layers with a white, 

sugary granulite.

The most accessible outcrops of this rock along the western side of 

the area are in the bed of the river near the stone mill just north of 

the Hinsdale station. The light and dark banded gneisses are tough 

and granitoid, and abound in epidote to an unusual degree. Several 

varieties of the rock can be studied at this locality:

1. A light-gray, flat, and thin foliated biotite-gneiss, so much like 

the newer, friable Becket gneiss that one is surprised at its toughness.

2. A coarser gneiss, with the greenish biotite segregated into broad, 

distant sheets and containing thin, lenticular layers of a coarse, reddish 

granite. Under the microscope the bands of granular quartz are separated by bands of granular epidote, which seem to have wholly 

replaced the feldspar. The biotite layers often contain much epidote 

and a secondary green chloritic mineral. The trains of pores run 

through several quartz grains and rarely show bubbles; only the 

smaller bubbles show motion.

3. A flesh-colored, thin-foliated gneiss, with greenish films and membranes of biotite, breaking with much difficulty and with little regard 

to the foliation. This grades, by the entire change of the feldspar, into 

a quartz-epidote rock.

The Lee gneiss occurs in fine and typical development in the high 

ridge that extends 2 miles north from Hinsdale cemetery. It includes 

heavy amphibolite beds and alternating bands of a white granulitic 

gneiss, with distant blotches of hornblende.

By following the main road north from the cemetery a little way past 

the top of a small hill, 1,040 feet high, large outcrops may be seen in the 

open field to the left, and here the coarse, white, greatly crushed granitoid beds are distinctly blotched by biotite, and by stretching the biotite 

is extended in long bands. The rock abounds in blue quartz, while one 

large amphibolite layer sends off apophyses into the gneiss like an 

eruptive. Northward, on the crest of the hill 1,720 feet high, the 

exposures are abundant and the true sedimentary structure is found, 

together with the secondary foliation produced by pressure. The two 

have uniformly the same strike, and the latter has generally a lower 

dip to the west than the former. At the quarry opposite the entrance 

to Windsor Falls the rock is extremely thin and fissile and superficially 

resembles the quartzite,«but it is really a very feldspathic crushed rock, 

and carries the dark-green amphibolite beds which are common in the 

Lee gneiss.

On the Hinsdale-Windsor road, along the east side of the schist area, 

the rock is greatly rotted in ledges by the roadside, and a little beyond, 

at the iron bridge, it contains beds of a curious white granulitic rock 

Bull. 159 3
S4 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

with coarse, distant hornblende blotches, while the same rock appears 

in picturesque ledges in the bluffs to the west.

In contrast with the broad area in the western limb of the anticline 

north of the Warner Mountain fault, south of this fault the Lee gneiss 

has a thickness of only 20 rods on the surface, and is concealed from 

this point south to the hill three-fourths of a mile southeast of Muddy 

Pond (see fig. 3, p. 36), where it is typically developed, and runs around 

south of Washington Station and the swampy ground, extending 

north therefrom in such a way as to render probable the presence of 

the Hinsdale limestone to the north.

TYRINGHAM GNEISS.

Along the west of the Hinsdale anticline the higher beds are faulted 

out of sight; along the east they are so covered that the Tyringham 

gneiss can not be mapped or found with certainty. At the south end 

of the area it comes in with great force and in most interesting and 

typical development.

At the deep cutting south of Washington Station the rock is a garnetiferous zircon-bearing biotite-gneiss of coarse fibrous or woody texture, 

rarely containing great blotches of a shining black hornblende. The biotite scales are wrapped around long quartz pencils, so that it is easy to 

note the dip and yet difficult to detect any planes of bedding. This peculiar structure of the rocks seems to be an extreme of the stretching common in the gneiss of the Cambrian series, especially east of the Connecticut. It was deformed under the influence of cornpressive forces which 

permitted flow in a single direction only. It weathers into a mass of 

quartz-feldspar rods, which are sometimes several inches long. This 

weathering is in itself quite exceptional. On the hillside above the 

cutting and along the road going south, large outcrops of the rock 

appear; it is crumbling into a mass of coarse granitic sand, and in the 

long cutting, which is in many places 10 to 12 feet deep, the decomposition extends everywhere below the bottom. This is a protected portion of the pre-Glacial weathering.

The wind blows the decomposed rock away like sand, exposing quartz 

veins and leaving large, rounded nuclei on the surface. The decomposition brings out in strong relief the peculiar structure of the rock as 

it falls apart into a pile of quartz-feldspar pencils, or long, flat rods the 

expression of the perfect stretching of the fresh rock.

WASHINGTON GNEISS.

The broad outer zone of this large anticline is formed by a rusty 

graphitic blue-quartz gneiss. It is in the main a biotite-gneiss, rusty 

from the decomposition of pyrite, pyrrhotite, ankerite, and hornblende.

It has associated beds of a heavy, black hornblende-garnet-gneiss 

which have been taken for emery, and in the whole circuit graphite is 

a never-failing accessory, especially in the upper portion, and it is occasionally so abundant as to tempt mining. o
EMEBSON.] WASHINGTON GNEISS. 35

Another equally persistent and very curious constituent of these 

gneisses is a blue quartz in flat laminae, 1 to 2 millimeters in thickness, 

which has often a deep tint of rich, purplish blue. It is so abundant as 

to form more than three-fourths of the mass, and furnishes very attractive cabinet specimens. Allauite is also a characteristic and abundant 

constituent of the rock, especially in its upper portion, and the puckering surrounding its black or red cross sections constantly calls attention to its presence in the rock.

In every part of the circuit of this anticline, and along the broken 

crest of the Dalton anticline, I have never failed to find beneath the 

next succeeding Cambrian conglomerate-gneisses all these characteristics of the top of the older series. Especially down the eastern side, 

the area above the limestone is marked by several broad bands of the 

rusty rocks, with intervening bands of biotite-gneiss. The latter rock 

is often so crushed that it is with difficulty distinguished from the 

Becket gneiss above, but there is not such a complete transition from 

the older gneisses into the white gneiss 1 as that described in the 

Hoosac area. The rusty blue-quartz gneiss is generally a membranous 

(" flaserig ") rock. Nearly continuous sheets of mica scales wind in and 

out and inclose the blue-quartz lenses and laminae. When this rock is 

involved in a crushing later than the formation of the blue quartz, 

the latter becomes gradually disintegrated at the edges and at last 

changes to a mosaic of small grains, and the pale-blue tint is lost in the 

reflections from the many fissures. By a careful search one can usually 

detect nuclei which show the color, and in this search the pocket lens 

is a great aid, as the blue color is thus easily distinguished from the 

blue grays of the quartz from the granites and Cambrian gneisses.

The Washington graphite-gneiss is absent along the whole western 

side of the syncline, being concealed by the fault and by the westward 

thrust of the body of the syncliue against the resistant mass of the 

Dalton syncline, until the south boundary of the latter the Warner 

Mountain fault is reached. South of this fault, at the Plunkett reservoir, the Washington gneiss appears, with a width of 2 miles, extending from the top of Warner Mountain, where the Becket conglomerategneiss can be seen dipping beneath it, to the top of the low hill which 

overlooks the great limestone bed 30 rods south of the bridge a mile 

south of Hinsdale. Its great width is attributable to its low dip eastward and its many undulations. It gradually narrows southward, and 

in the high hill three-fourths of a mile west of Washington Station 

it bends westward and forms the great loop which extends west past 

Washington Center, where it can be conveniently studied.

It is everywhere a coarse muscovite-gneiss, with some biotite, and so 

abounding in pyrite that it rots into a mass of rusty fragments, and is 

usually rusty externally. The content of graphite in clear crystalline

1 Puinpelly and Wolff: Mon. U. S. Geol. Survey, Vol. XXIII, pp. 72,85.
36 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

scales is nearly constant, and its amount increases with the increase in 

the rustiness. When not crushed it abounds in bauds of blue quartz, 

sometimes 2 to 3 inches thick, which disappear with increasing granu 

lation. This granulation gives a peculiar sandy look to the rock, 

different parallel layers of crushed quartz being now white, now rusty, 

as the crushed mass was influenced by the rusting of the pyrite. Small 

bands of impure limestone, now mostly changed to a pale-green saliteactinolite rock, appear, and the graphite is often so concentrated in 

them that they have been mined.

Such a bed appears in the brook crossing the road a few rods west 

of the overhead bridge on the railroad a mile south of Hinsdale, and, 

as a line of big salite-actinolite bowlders, can be followed a mile farther 

south along the crest of the hill above the big limestone bed.

The contact on the Becket gneiss is very clear at the signal station 

on the apex of Warner Mountain, the highest point west of Hinsdale 

village, but across Washington and Becket to North Becket the Washington gneiss is much of the way wholly crushed and the blue quartz 

destroyed, and in. many beds the content of pyrite is small. Where

'M ' A* "4

Fit). 3. Section at lead rnino east of Washington Station. b, white friable biotite-gneiss (Becket 

gneiss); Aw1 , white hornblende spotted gneiss (Washington gneiss); Aw2, granulite (garnet-gneiss); 

Aw3, rusty graphite-gneiss; At, stretched biotite-gneiss (Tyringham gneiss); Al, light-gray biotitegneiss (Lee gneiss); L, limestone; A, amphibolite.

this is the case the graphite is rare, for graphite and pyrite go together. 

Along this line the Becke't gneiss is exceptionally crystalline and coarse 

grained, so that it is with difficulty distinguished from the Washington 

gneiss. The Becket gneiss is, however, a pure biotite-gneiss carrying 

many large garnets, which are absent in the Washington gneiss, and 

it is rare that a ledge of the latter will not furnish considerable graphite. Along the east side of the area the country is covered by surficial 

deposits, and the last place for study is east of Washington Station, 

where the outcrops are abundant.

FSllowing the road from the station a mile east, to a point where it 

runs north and south, north of a small pond we find the road to be the 

boundary between the Becket on the east and the pre Cambrian on 

the west. Going over the great bare hill we have the following section 

ending with the lead mine and giving the whole thickness of the Washington gneiss (PI. I, fig. 3). The great beds of white gneiss'are quite 

exceptional and are exceedingly like the Cambrian at first view. They 

are, however, more feldspathic, and their scanty black constituent is 

mainly hornblende.
EMEESON.] WASHINGTON GNEISS. 37

PETROGRAPHICAL DESCRIPTION CAUSE OP THE BLUE COLOR IN THE QUATITZ.

Blue-quartz gneiss. At Peru, near the residence of H. A. Messinger, 

a mile northeast of the bridge over Ashmere reservoir, there is a rusty, 

fine-grained gneiss (PI. I, fig. 2), with little mica (biotite) in distant flat 

sheets of small scales, and with greasy blue quartz in grains and flat 

plates 1 to 3 millimeters thick, which often coalesce into parallel layers 

of considerable extent. These layers are plainly secondary infiltrations 

in a fine granular ground which has the aspect of a fine sandstone or 

quartzite, while they have much the position of the quartz blades in a 

graphic granite. In a plane at right angles to the dip they appear as 

rounded or slightly flattened ends of blades, which have their flat sides 

in the foliation plane and are often greatly elongated parallel to the 

dip. Under the microscope this ground proves to be an exceedingly 

fine-grained mixture of quartz, orthoclase, microcline, and abundant 

minute scales of muscovite; and it is such a structure as may have 

been produced by the crushing of granite and the change of most of its 

feldspar into muscovite. It is .shown in three bauds, of varying width, 

running across the slide. The darker shading in these bands represents a concentration of rust which permeates the whole layer.

The blue quartz, which crosses the slide in four bands, contains lew 

minute broken rutile needles, rarely cavities containing small, rapidly 

moving bubbles, and many rudely parallel sheets of very fine cavities 

or grains of some unknown mineral. There are a few distant fissures. 

It shows strong undulose polarization, which appears in broad patches 

of deep shade elongated with the length of the bands and moving 

across them. This is indicated by the shading of the bands in the figure. 

The whole of each of the bands of the blue quartz polarizes as a single 

individual, however large it may be. The sections were cut at right 

angles to the foliation and about parallel with the dip or stretching of 

the rock. It is interesting that in each case they are cut at right angles 

to the optical axis, and the slide can be moved from one end to another 

of the blue quartz bands, 1 to 2 millimeters wide and 15 millimeters long, 

and the optical figure remains sharply defined, regular, and unchanged.

A fragment heated for a long time with the bellows blowpipe retained 

its color without perceptible change. Even in the thin section the 

quartz shows a rich blue, like a fluorescence, when examined by transmit! ed light and without a lens.

At Washington, on the north line of the road to Pittsfield, there is 

a coarse membranous biotite-muscovite-blue-quartz-gneiss (PI. I, figs. 

3-5). Broad continuous films or membranes of fine scales of biotite 

and muscovite, one of which runs through the middle of the figure 

(which represents a transverse section of the rock), wrap around layers or lenses, from a half inch to an inch wide, of a fine granular buffcolored mass, or around feldspar augen. This granular mass, which is 

shaded in the figure, is a quartz mosaic with very many regularly distributed muscovite crystals replacing most of the feldspar.
38 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

The blue quartz, in grains or flat lenses, shows a preference for a position between the membranes of mica and the fine granular groundmass, and seems to be a late addition to a crushed biotite-gneiss. In 

the figure the blue quartz separates the mica film from the granular 

mass on both sides. It contains broad sheets of small grains and pores, 

with moving refractile bubbles and few cracks. It shows undulose 

extinction, which is represented by the soft shading upon PI. I, fig. 3. 

Each band is a single crystal, at least for a long distance, and in the 

broad band at the bottom of the figure the slide was moved 8 mm. 

without any movement of the axial cross.

The most striking and instructive things about the slide are, first, 

that the blue quartz shows, in spite of its great thinness, an opalescent 

blue color almost as clear as in the hand specimen, and, second, that 

the blue color is absent in irregular spaces, mostly along the borders, 

though the quartz does not show any other distinguishing feature and 

is only rarely separated from the rest by a visible fissure.

In fig. 4 of the plate, which is an enlargement of the lower portion of 

the upper quartz band in fig. 3, the colorless portions are distinguished 

from the rest by being dotted and by a dotted boundary. In fig. 5 of 

the plate the same is drawn with crossed nicols, and it is seen that the 

portions which were colorless appear, in polarized light, broken into a 

mosaic whose grains, being relieved from tension, polarize with sharp 

uniformity, while the blue portions show strong undulose extinction, as 

is indicated by the central shading. It is thus quite evident that the 

blue color is due to strain, which is effective in a very thin layer, and 

that the strain is relieved and the color discharged by the crushing ot 

the mass to a mosaic.

It is curious that a double series of rhombohedral cleavage lines runs 

through the broadly crushed portion figured and extends beyond it into 

the uncrushed portion without relieving the tension. The quartz is 

often crushed at the border and even clear into the center, but with the 

lens the blue color can be seen until the crushing is complete.

I first found these blue quartzes as grains in the gneissoid Upper 

Devonian conglomerates of the Bernardston series in West Northfield. 

Soon after beginning the study of the pre-Cambrian around Hinsdale 

I remarked the constancy of the blue quartz as a characteristic of the 

pre-Cambriah rocks of the region. On visiting Professor Wolif I found 

that he had noted the same thing and had made microscopical examinations of the rocks, and thought that the structure might be caused 

by strain 5 but he does not discuss the matter in the final report.1

Later, on examining crystalline rock from the southern Appalachians 

at the Survey office in Washington, I was struck by the prevalence of 

the same lavender color in the quartz; and finally, in a collection of 

rocks from Smiths Sound, in the Arctic region, obtained by Hayes and 

presented to Amherst College, I found a large specimen of the finest 

blue-quartz gneiss I have ever seen. It is a rich deep blue, like the

1 Geology of the Green Mountains in Massachusetts, Mon. U. S. Geol. Survey, Vol. XXIII, p. 46.
EMERSON.] DALTON ANTICLINE. 39

finest cordierite, and is in a layer more than an iucli thick extending 

across a large specimen. I have observed the same thing in the 

Archeau gneiss at Gutwagen in Norway, in porphyries in Finland, and 

in the granites and quartz-porphyries which extend from Marlboro, 

Massachusetts, to Providence, Rhode Island.

It is a peculiarity of this coloring that it is best observed with a 

lens, which detects immediately if it is the true color of the quartz and 

not a grayish blue depending upon impurities or some fine corrugation 

of the surface.

The foregoing facts concerning the crystalline continuity of the blue 

quartz layers and lenses for considerable distances, their strained 

appearance, and their tendency to form on one side of the mica films, 

or, as in the center of PI. I, fig. 4, on both sides, make it probable that 

they have entered into the composition of the rock at a somewhat late 

stage, and have since been only partly crushed and incorporated into 

the general mylonitic mosaic.

An antecedent state of many of these rocks may have been a wellcrushed biotite-gneiss, and it is interesting to see how diverse the 

crushed masses are in the preceding examples.

In one case the rock is a large-grained plagioclase niass, regularly 

crowde.d with small sharp epidotes; in another it is almost all microcline, similarly but not so abundantly filled with epidote; in another 

case the epidotizatiou is carried so far that little feldspar remains; in 

still another the crushing has changed the larger portion of the feldspar into a mass of small, stout, muscovite crystals.

Except when the large and strongly warped cleavage faces of the 

feldspar appear still uncrushed, this ground has a very clastic appearance and the blue quartz seems to be connecting thin bands of a firm 

quartz-sandstone.

This structure in the gneiss illustrates a tendency of the quartz to 

undergo torsion, or bending, rather than to become granulated under a 

pressure which would completely crush the other constituents.

DALTON ANTICLINE.

This is- a normal flat arch with the Cambrian conglomerate-gneiss 

worn oft' from the crest, exposing the upper portions of the pre-Cambrian. (See fig. 4, p. 40.) The crest of the arch runs south from Dalton 

along the top of Warner Mountain, the north end of which is in Dalton called Day Mountain, and near the line between Dalton and Hinsclale;

The site of the Dalton clubhouse, a mountain house on the top of 

the high flat hill overlooking the Dalton railroad station, 1,840 feet 

above sea level and three-fourths of a mile south of Dalton, is a convenient landmark by which to find this most interesting contact of the 

conglomerate upon the older gneisses. 1 The clubhouse, locally called

1 For description of tlio conglomerate contact see page 75,
40. GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

"the Chalet," is now removed, but the foundations still remain, and 

the road can be followed from the station, the clearing making a notch 

in the woods at the top of the mountain visible from Dalton.

The pre-Cambrian, at the contact a few rods southeast of the clubhouse, is a fine-grained crushed granulitic gneiss, but abundant beds 

of the rusty blue-quartz gneiss come in just east of this. Farther 

south the blue quartz is everywhere abundant.

Along the boundary, going southwest to the brook which runs through 

the pasture south of the clubhouse, allanite is an exceedingly abundant accessory in the gneiss, a dozen crystals often appearing in a 

single hand specimen. It is especially abundant near a large tree at 

the middle outcrop of the brook bed, indicated in the figure.

A little farther up the brook bed is a very peculiar granular quartz 

rock containing considerable feldspar and calcite in large, rounded 

balls, often 3 to 4 inches across, which consist of one or a few crystals

FIQ. 4. Dalton anticline: The Dalton clubhouse section on Day Mountain south of Daltoii. Cambrian 

conglomerate-gneisses arch over the pre-Cambrian uncomformably.

and show very large cleavage surfaces, presenting the finest twin striation. These balls are sometimes blended into masses of very coarse 

marble as large as a man's head. There is much pyrrhotite developed, 

especially along the borders between calcite and quartzite, and biotite 

also occurs in the calcite.

At the south end of the mountain ridge the pre-Cambrian terminates 

in a fine bluff overlooking the Warner Mountain or South Dalton fault. 

At the southwest corner it dips under well-marked Cambrian conglomerate-gneiss and shows heavy hornblende-gneiss beds in graphitic bluequartz gneiss. The southeast corner is three-fourths of a mile IsT. 20° 

W. of the signal house on the top of Warner Mountain, and the sudden 

ending of the blue quartz gneiss against the fault is clearly exposed.

The schist upthrusts in the Stockbridge limestones, which are prominent farther north and disappear in the latitude of Pittsfield, opposite 

the Dalton anticline, the lesser folding of these limestones compensating 

for the Dalton anticline.
EMEHSON.] PBE-CAMBEIAN ROCKS. 41

COLES BROOK LIMESTONE.

A remarkable linear outcrop of the Hinsdale limestone 7 miles long has cut through the Cambrian 

gneisses like a knife, from Factory Hollow, in Middlefield, to the south part of Becket. It is bounded 

everywhere by faults, is accompanied by only narrow 

selvages of the pre-Cambrian gneisses, and, unlike all 

the other outcrops of the limestone, forms a series of 

high, steep ridges. It is best exposed a mile northwest of Bancroft Station, in Middlefield, where the 

Boston and Albany Eailroad cuts off a loop of the 

Westfield Eiver and Coles Brook enters this loop from 

the north. The Cambrian gneiss overlaps the preCambrian unconformably on either side. 1

The white Cambrian con glomerate-gneiss in synclinal posture mounts unconformably on the older Lee 

gneiss, which consists of a great thickness of a wavy 

bedded gneiss of fine grain and almost black from the 

abundance of black biotite.

The Lee gneiss abuts, apparently by a fault, certainly by a wholly abrupt transition, upon a band of 

the coarse, white, almost micaless Hinsdale gneiss, 

with iridescent feldspar, which is 23 feet wide below 

but narrows above.

This is followed by a bed of white, thin-bedded, 

highly crystalline limestone 50 feet wide, with thin 

films of serpentine, which is separated, by 108 feet of 

the same dark Lee gneiss, from a second band of similar limestone, of which only 29£ feet are exposed. 

The partial serpentinization of the chondrodite has 

here produced a yellowish verclantique which furnishes very beautiful hand specimens and might be 

useful for ornamental work.

Following tliis, in the brook bed at bridge 142 and 

in the railroad cut, is a large mass of the dark gneisscarrying beds of hornblende-schists, until we come to 

the fourth telegraph pole from bridge 142, upon the 

fine unconformity where the conglomerate-gneisses 

mount the dark pre-Cambrian gneiss.

Between this point and Middlefield Station the cuttings expose a long extent of contorted and twisted 

rocks, mostly of Cambrian age, the beds swinging 

round from horizontal to vertical within a few feet.

Gradually a low dip eastward predominates, which 

becomes steeper, and a baud of hornblende-gneiss 10

wsr

1 The whole section is figured and described by the author in Mou. TJ. S. Geol. Survey, Vol. XXIX, 

pp. 21-24.
42 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

 feet wide sets in, while at the signal house a boss of coarse Hinsdale 

gneiss and calcareous salite actinolite-schist protrudes. East of the 

unconformity all is Becket gneiss, except the few hornblende-gneiss 

masses and the last-mentioned fross of Hinsdale gneiss, which are 

brought just above the railroad level by the undulations of the Becket 

gneiss.

The limestone can be followed a considerable distance north along 

the brook, and it gradually passes to the east bank. Its most northern 

outcrops are south of the schoolhouse at Factory Village, in Middlefield, 

and the long depression, occupied by the pond, which extends north from 

this point has been formed by its solution. To the west are heavy 

hornblende-gneiss beds (Lee gneiss).

South from Coles Brook the limestone rises in a great hill south of 

the Middlefield railroad station, where it is 330 feet thick and is inclosed 

in a fine granulite.

Westward, toward Becket Center, a ragged, castle-like ledge of calcareous actinolite-gneiss, much contorted, forms the bi.re crest of the hill 

south of the road, and just east of this ledge is a bed, 75 feet thick, of a

FIG. 6. The Colea Brook limestone, enlarged from fig. 5.

coarse, well-bedded chondroditic limestone standing vertically. It is 

full of nodules, often 15 inches across, consisting of salite, tremolite, 

titanite, and chondrodite. Other nodules are wholly of pale-green 

bladed tremolite. On the south of this hill the limestone is exposed 

with a thickness of 250 feet, aud-farther south, where it crosses the road 

(at the house of Ellsworth and son), it is 660 feet wide. Where it crosses 

Walker Brook and the last road on the quadrangle, the limestone is 

exposed to a thickness of 100 feet, and can be followed south across a 

blind road, turning south from the main road to a house known locally as 

"the old Conn place." Just south of this house great masses of the bluequartz graphite-gneiss accompany the limestone, which can be traced 

but a little way farther south, as the Becket gneiss closes in on it.

The limestones Of this locality are first noted by President Hitchcock 

in his final report 1 as occurring in the west part of Middlefield on Pontoosuc turnpike, on the railroad at the mouth of Coles Brook, and 1 

mile east, in the southeastern part of Becket. The first two localities 

are on the Coles Brook bed; the third was a line of great bowlders 

from this bed. The description of the Hinsdale Station limestones

1 1841, pp. 81, 85, and 567.
EMERSON.] GULF ANTICLINE, DALTON. 43

FIG. 7. Hinsdale limestone at Alderman quarry, 

Lower section 10 rods south of upper one.

Becket.

given on pages 27-28 will apply wholly to those of this locality, and the 

change of chrondrodite into serpentine may be better followed here. 

The former rock is, however, coarser, and the included minerals are in 

larger individuals and therefore better fitted for mineralogical study.

LIMESTONE ON THE ALDERMAN FARM IN BECKET.

A mile east of Center Pond, in Becket, a thick bed of pre-Cambrian 

limestone has been opened. It has a width of 82 feet, and is a coarse 

chondrodite-phlogopite 

marble. At its eastern 

contact is a selvage, 4 

feet wide, of pale-green 

or partly olive-green 

actiiiolite pyroxene rock, 

which consists for the 

most part of a loose network of coarse actinolite 

blades, with some large 

masses of pale-green pyroxene and pyrite. It 

contains amethyst, much 

titauite in the usual flat 

crystals, and orthoclase 

in small well-formed crystals with simple forms, rounded edges, and 

blue opalescence. The bed is bordered on the east by 3 to 4 feet of 

a dark-banded gneiss of the type of the Lee gneiss, and the whole is 

inclosed in the Becket gneiss. About 8 rods south (see lower section of 

fig. 7),in the line of the strike, appears a great bed of a black hornblendeschist, which rests against the vertical Becket gneiss on the east, while 

the same gneiss appears in its proper place on the west, the intervening space being low covered ground. This hornblende-schist seems 

clearly to be the continuation of the limestone. It was prospected 

quite extensively, first for copper and then for emery. A study of thin 

sections showed it to be a hornblende-biotite-garnet-gueiss, with little 

black ore and much leucoxene and plagioclase.

GULF ANTICLINE, DALTON.

North and northwest of Dalton the country rock seems to be entirely 

the massive quartzite, but going north by the second wood road, 

after passing the highest point on the "Gulf road," 30 rods from the 

highway, one finds outcrops of the gray Becket gneiss. Twenty-five 

rods above is the coarse, flesh-colored, pre Cambrian biotite-gneiss, with 

blue quartz. This can be followed a long way up the brook, to the 

point where the main wood road crosses the brook, near an old cellar and 

80 rods from the "Gulf road." The pre Cambrian here extends west 

beyond the woods into the open pasture, and continues in that direction
44 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

across 40 rods of Becket gneiss, to the long, bare ridge of quartzite 

which overlooks the railroad on the west. It can be followed still 

farther north, to its apex on the high, bare hill, at an altitude of 1,720 

feet. Here is a broad, bare hilltop .of the Becket gneiss, and at the 

southwest portion of the flat is the northern apex of the pre-Cambrian 

a green, calcareous, highly feldspathic gneiss carrying dark-green 

fibrous hornblende, titanite, and blue quartz. The Becket gneiss wraps 

around it, and the contact is perfectly exposed. The Becket gneiss is 

conglomeratic at the south. A band of Becket gneiss about 40 rods 

wide surrounds the entire pre-Cambrian area, and the quartzite surrounds the whole. The axis of the anticline runs northeast, and the 

di'ps are a'll southeast, the anticline being overturned to the west. 

Mr. Benjamin Newell sent me specimens of the fresh rock from a point 

about 2 miles northeast of Daltou, and a specimen of coarse feldspathic 

pre-Cambrian gneiss, full of half-inch spots of a biotite-garnet aggregate. This is directly on the line of the axis of the gulf area of 

pre-Cambrian described above, and indicates a small pre-Cambrian 

area on the south border of the Greylock quadrangle.

LEE-TYRINGHAM AREA.

DISTRIBUTION.

This is the largest pre Cambrian territory in western Massachusetts. 

It begins in a lobe overlooking Sackett Brook, in the south part of

FIG. 8. Section of contact of Cambrian on pre-Cambrian east of Lenox Fnruaco.

Dalton, where it is a slightly overturned anticline. It expands between 

Ashley Brook and Roaring Brook as a normal anticline, with axis running north and south. '1 his is connected by a narrow isthmus with the 

larger and more important area, which begins on a fault in the high 

ground southwest of New Lenox, expands rapidly across Washington, 

occupies all the high ground in Lee and Tyringham, and ends in the 

great mass of Kingsbury Mountain, against the Tyringham fault.

It is convenient to treat separately the further extension south of this 

fault as the Sandisfield area (see page 55).
EMERSON.] LEE-TYRINGHAM AREA. 45

The eastern boundary of this area is nearly everywhere normal, being 

formed by the Cambrian gneisses, which are often conglomeratic. It 

extends southeastward across Washington, with several great lobes 

running northward to a point south of Becket Center, where it turns 

south westward, becomes an unconformable boundary, and, crossing into 

Otis, east of where the Tyringham Kiver enters the town, extends southwestward to West Otis, where it meets the Tyringham fault.

Between New Leuox and East Lee the western boundary runs at the 

foot of the bluff overlooking the 

Housatonic Valley, and is a line 

of fault, with downthrow on the 

west and some westward overthrust. (Seefigs.Sand9.) Along 

this line the western half of the 

Lee-Tyringhain pre Cambrian 

dome is absent, and the Cambrian white gneiss and the lower 

part of the quartzite are carried 

down and concealed, the differ 

eutbeds of the pre-Cambrian on 

the east coming successively 

into contact with the quartzite 

on the west. (See PI. VII, p. 86, 

and section D E.) East of East Lee the fault bends sharply, influenced 

by the northward thrust of the country to the south, and in the hill 

south of East Lee the boundary changes from an overturned and faulted 

contact to a normal contact, the Cambrian gneiss mounting unconformably over the pre-Cambrian gneisses.

TIG. 9. Layer of Cambrian slate on vertical Lee gneiss 

(at B, iig. 8), Lenox Furnace.

STRUCTURE.

Greenwater Pond anticline. Along its northeastern border the Washington gneiss includes a wide band of Becket gneiss in a normal 

syncline which extends across Washington and Becket. West of this 

the Tyringham gneiss crops out over a broad area of great monotony. 

Still farther west is the curved axis of the important anticline of Greenwater Pond.

Limestones lie along the bottom of the deep valley. The steep walls 

are composed of the heavy black Lee gneiss, above which the barren 

Tyringham gneiss extends in low undulations a long way north and 

south, and finally sinks below the Washington blue-quartz gneiss. 

The axis of the Greenwater Pond anticline is continued beyond Shaw 

Pond and ends in the middle of the area, where it is covered by the 

uncomformable Cambrian gneisses.

East Lee anticline. A mile east by south of East Lee another small 

but very interesting anticline, with eastward pitch, exposes the limestone bordered by the Lee gneiss.
46 GEOLOGY OF EASTERN BERKSHIRE COQNTY, MASS. [BULL. 159.

Goose Pond anticline. A mile farther on, Goose Pond lies in the 

bottom of a curved anticline, with axis pitching south and east at either 

end, which also exposes the pyroxenic limestones.

The deep' valley in which lie Goose Pond, Long Pond, and its tributary brook has been formed by solution of the-limestone. It overflowed for a long time into the Tyringham Yalley, wearing a deep 

trench down the mountain side. This valley seems to have been tapped 

by the wearing back, along the axis, of the Bast Lee anticline.

The Goose Pond anticline is symmetrical with the Lee-Becket anticline in its Long Pond portion, and bends around in sympathy with 

the East Lee and Tyringham anticlines in its western portion. It has 

thus a curved shape like the Bear Mountain anticline (see p. 58).

The axes of these folds end abruptly on the west against the important fault that runs at the foot of the bluff from New Lenox to East 

Lee, which may be called the Lenox fault. The western prolongation 

of each of these anticlines was thus dropped below the level of the sea, 

in Cambrian times, and covered by the Cheshire quartzite and the 

Stockbridge limestone.

Foxden anticline. The next interruption to the expanse of the 

Tyringham gneiss is a broad anticline of the banded Lee gneisses, 

which begins a mile and a half east of the outlet of Goose Pond, 

crosses the next road south, with a width of nearly a half mile, and 

ends unconformably a mile south of this road at'a large ruined house, 

locally called Eoxden, overlooking the Tyringham Valley.

The exposures here show perfectly the anticlinal position of the 

white-and-black banded gneisses in the stretched Tyringham gneiss, 

and the unconformable overlap of the white Becket gneiss upon the 

denuded anticline. Only a trace of limestone was found in the core of 

this anticline.

Hop Brook anticline. The last interruption to the Tyringham gneiss 

before reaching the Tyringham fault is the Hop Brook anticline, 

at the foot of the Tyringham Valley. It is very interesting, both 

because of the abundance of fine minerals from the limestones of its 

core which have been found by Mr. Daniel Clark, of Tyringham, and 

from the light it throws upon the blocking out of the pre-Cambrian 

^valley, into which the deep waters of the Cambro-Silurian sea penetrated, 

for the deposition of the calcareous beds now altered to the Stockbridge 

marble.

At the mouth of Hayes Pond, southeast of the valley, is a bed of 

green pyroxene-actinolite rock 40 feet wide, which, with the associated 

gneiss, represents the east end of the core of a long, narrow limestone 

anticline. .The white-and-black banded gneisses wrap round the core 

and pitch steeply east, and can be followed across the pond and up the 

hill a half mile northwest, where they run under the Cambrian gneiss. 

They can be seen bending around from a south to a west strike at the 

house a little way south of the pond, and thence extend west to the
LEE-TYRINGHAM AREA.- 47

Tyringhain fault. The last green actinolite beds of the core are near this 

house, and the deep erosion of Hop Brook has exposed the core, with 

many impure limestone beds, still farther west, to a point about 20 rods 

from the small settlement called Sodom, in Tyringham. They here go 

under the Cambrian gneiss, reappearing 4 miles down the valley at the 

Brookside mill, in the village of Tyringham, where, below the dam, the 

inipurepre-Carnbrian limestone, with chondrodite, wernerite, and titauite, appears beneath a low arch of Cambrian tourmaline-bearing gneiss, 

and is continued westward in a small isolated area of blue-quartz 

gneiss, which is exposed along the road running west down the Tyringham Valley from the mill to the town line. On the hillside above is a 

thin veneering of Becket gneiss, which has been worn off in the bottom 

of the valley. Blue quartz occurs in the striking cliffs by the roadside 

near the town line.

GENERAL PETROGRAPHIOAL DISTINCTIONS.

Beneath the white Cambrian gneisses which border the area the 

Washington blue-quartz gneiss appears everywhere. Below this is a 

coarse biotite-gneiss, which is. quite uniformly free from all accessory 

minerals and from beds of any different rock type. It is so highly 

stretched that it Shows a ligniform, or small columnar, rather than a 

common foliated structure. I have called it the Tyringham gneiss.

It rests on a thick bed consisting of well-banded alternations of white 

granular gneiss and heavy black hornblende-gneiss or hornblendebiotite-gneiss, which I have called the Lee gneiss, and this rests upon 

the impure limestones which appear in the core of the anticlines.

The Lee gneiss is practically a calcareous facies of the gneiss in the 

neighborhood of the heavy limestone beds, and it sometimes seems to 

pass laterally into the Tyringham gneiss.

Hinsdale gneiss. This rock is absent in the Sandisfield area, as the 

limestone is nowhere cut through to show the rocks which underlie it. On the road from Lenox Furnace to Washington occur bowlders 

of a coarse, zircon-bearing biotite-gneiss which closely resembles it 

but which could not be found in place.

Hinsdale limestone. The fact, first suggested by Professor Dana,1 

that the removal of the limestone has formed many of the lake basins 

and valleys in this beautiful lake region, is of great value in the study 

of the distribution of this rock. The two valleys at East Lee, and the 

continuation of the more northern across the low col into the Farmington Eiver Valley, Goose Pond, and several ponds in Sandisfield, are 

illustrations.

Observation is difficult, as the rock is covered by drift and water in 

bottoms of the valleys and must be studied mostly in bowlders. It 

is never exposed in beds so great as those in the Hiusdale area and 

is never so pure as there.

'The South Lee, the Hinsdale, and the Tyringham valleys are instanced as showing the influence 

on the outline of the Stockbridge limestone areas exerted by preexisting Archean channels or bays. 

J. D. Dana, Am. Jour. Sci., Vol. XXXIII, p. 276.
48 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

It is a coarse-grained, greatly gnarled and twisted rock, deeply 

weathered in the great bowlders which cover the surface where it 

occurs. It contains pyroxene and hornblende varying in color from 

deep green to white, phlogopite, muscovite, biotite, chondrodite, wernerite, titanite, chlinoclore, orthoclase, graphite, quartz, pyrite, and 

pyrrhotite.

Several of these minerals are always present in large amount, in 

varied and often quite characteristic groupings in different parts of 

the area; For instance, chondrodite is found most abundantly in masses 

larger than the two fists on the hill southeast of East Lee, wernerite 

north of Otis and in the bottom of the Tyringham Yalley, and titanite 

in the northeast corner of Saudisfield, etc.

One mineral common in similar limestones is absent in this region. 

This is spinel, which is, however, found just south of this district, in 

Norfolk, Connecticut.

Lee blade gneiss. In the bluffs which border the East Lee Valley on 

the north and its continuation across Becket occur thick beds of a 

black, very heavy hornblende-magnetite-biotite-gneiss, which occupies 

a very constant position above the Hinsdale limestone and becomes a 

horizon of great value.

It represents a calcareous transition band above the limestone. A 

thin bed of a rusty graphite-pyrite quartzite seems to separate it from 

the limestone on both flanks of the East Lee Valley, but could not be 

found in place.

Along the south side of the valley and on both sides of the next 

valley to the south, by which runs the road to Goose Pond, the rock is 

still more strongly magnetitic, so that it is often prospected for iron, 

especially' on the high hill a mile southeast of East Lee. It also 

abounds in large iron garnets, and this peculiarity can be traced along 

the north side of the East Lee Valley into Becket. Along both sides an 

upper bed is leek green and pyroxenic.

This rock also appears in considerable force in the crest of the high 

ridge north of East Lee, and may be studied by going up the hill road, 

starting 30 rods east of the East Lee Hotel. At the 1,400-foot contour 

the woods begin, and at the'northwest corner of the clearing, are two 

apparent ledges, which I assigned to the Becket gneiss but found to be 

great bowlders of the same. From this point a wood road runs up over 

the black hornblendic gneiss for 30 rods, and the rock ends where this 

road emerges in a clearing on the crest of a hill. Here it is a black, 

medium-grained rock, thin splitting and flat bedded. It is an anorthiteamphibolite, and a thin section (No. VI, 131a, National Museum Collection) of the black foliated rock cut transversely showed only a trace 

of quartz, little partly bleached biotite and magnetite, and no titanite. 

The green, moderately dichroic hornblende is not fibrous, but is in 

stout, ragged blades appearing in all directions in the slide. The 

centers of the blades contain many impurities.
EMERSON.] LEE-TYRINGHAM AREA. 49

The pleochroism is: a = yellow, b = yellow-green, c = blue.

The mosaic of anorthite occupies half the surface; about half shows 

multiple twinning with large angle of extinction; half the remainder 

shows concentric extinction, but no twinning. It incloses much hornblende in small plates and in minute straight needles.

The feldspars have very generally a common orientation, so that in the 

field they show a positive obtuse axis eccentric, with the axial plane 

about parallel to the twin striation.

There was nothing in the section that would lead one to think it an 

eruptive, and all its associations connect it with the calcareous gneisses.

A little west of the wood road before mentioned, the rock is white-andblack banded and is greatly twisted in its bedding. Farther west the 

quantity of hornblende diminishes, and north of the before-mentioned 

Becket gneiss bowlders it disappears and the rock graduates, with the 

strike, into the stretched Tyringham gneiss. It can be followed east as 

far as the limestone ledge, and here also it becomes a light-colored 

slightly hornblendic gneiss.

It is subordinate to the Tyringham gneiss, but as it borders the 

limestone areas in the different valleys for so long a distance it seemed 

well to maintain its distinctness within the area.

Where the band crosses the blind road on the mountain, a mile farther east, at the point where this road runs most northerly, it is a ribbon gneiss of many small hornblende bands interleaved with white 

gneiss bands.

On the southern side of the valley it can be best studied in the hill 

south of the hotel in East Lee, and is described in connection with the 

Hinsdale limestone. (See p. 33.)

It is well exposed along the desolate road which runs from Tyringham 

Valley over the mountain to West Becket as a series of markedly flatbedded gneisses, of fine grain, which for nearly a mile across their strike 

present a continuous alternation of black and white beds from a fraction of an inch to 12 feet in thickness. The white beds have the appearance of quartzite, but are a compact quartz-feldspar mixture which 

looks as if it had been thoroughly crushed and recemented. The black 

layers are black from the great quantity of biotite and hornblende, and 

some beds are a heavy, black granular hornblende rock which resembles crushed tourmaline.

Tyringham ligniform gneiss. This gneiss is, in perfect development, 

composed of bundles of quartz-feldspar pencils wrapped round' with 

biotite. The dip is easily obtained but the strike often with difficulty. 

The rock is best developed across the center of Tyringham on both 

sides of Goose Pond. It is a coarse biotite-gneiss of very uniform 

character, barren of all accessories. Its biotite is gathered in elongate 

films more or less wrapped round the other constituents, and is generally rather dull black. The rock is very prone to decomposition.

Washington blue-quartz gneiss. The.peculiar lavender quartz so charBull. 159 4
50 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. '[BULL. 159.

acteristic of the pre-Caiubriaii in the Appalachians is found in all the 

members except the limestone, but in the upper horizon it becomes 

extremely abundant and characteristic, so that it is the most constant 

guide to the settlement of the boundary between pre-Oambrian and 

Cambrian.

The rock is a coarse biotite- or biotite-muscovite-gueiss. Pyrite is a 

uniform and often abundant constituent, and the rock is always rusty. 

Graphite, so uniformly abundant and characteristic of the rock in tbe 

Hinsdale area, is found in quantities only part of the way across Washington, but reappears much farther south, in Saudisfield and New 

Marlboro.

Allanite, which is also abundant in Hinsdale, appears frequently in 

Becket and Tyringham.

The blue quartz appears in scattered nodular masses, often nearly an 

inch thick and fusing together into films on the foliation plane, and 

when the rock contains also large garnets and allauite, with the peculiar 

puckering around the crystals, it is beautiful and striking. The quartz 

is often granulated by crushing till only a small center remains, and 

the color is then wholly discharged. This crushing into a white sugary 

sand is very characteristic of the rock.

Where it crosses the road north of Ashley Brook it is a very coarse 

granite gneiss, like that of Hoosac Mountain. The feldspars are often 

4 inches across, at times resembling pebbles and having broad, curved 

cleavage faces. The blue quartz bauds are sometimes 2 inches thick. 

Other beds are crushed to a fine granulitic rock, with flat, elongate, 

blue quartz seams.

The gradual granulation, by crushing, of the blue-quartz grains and 

bands, accompanied by an apparent discharge of the blue color, is very 

clearly exhibited here in all its stages.

The gneiss along the road from the outlet of Ashley Lake to Few 

Lenox is a coarse to very coarse, granitoid, highly feldspathic, bluequartz gneiss. Many layers are full of large manganesian garnets, often 

an inch across. The biotite is in distant membranes, branching out 

into masses an inch across. It winds in and 'out among feldspar or 

feldspar-quartz nodules 1 to 4 inches across. There is often much 

coarse tourmaline.

LIMESTONE AREAS.

East Lee limestone. The deep valley which starts at East Lee and 

runs-in a great curve southwest to Otis, containing Greenwater and 

Shaw ponds, is underlain by Hinsdale limestone and owes its position 

and shape mainly to the solution and removal of the same.

It is deeply covered by drift, which fills the valley, and can be best 

studied upon the high, bare hill between the two roads running east 

from East Lee. It is a coarse, white, highly crystalline limestone, 

coarser and of more translucent grain than the adjacent Stockbridge 

limestone, very impure, and coarsely warty upon the surface, from the 

solution of the purer parts.
EMERSON.] LIMESTONE AREAS. 51

It contains actinolite, pale-green and black pyroxene, phlogopite, 

aud, most important, chondrodite, and in the hill above mentioned this 

mineral occurs in granular masses of the pure substance as large as 

one's fist and in rude crystals an inch long. Wernerite does not appear 

in this band, as it is not common in the limestone except near faults.

The mouth of the valley is greatly clogged by thick drift deposits, in 

which immeuselimestone bowlders are common, and by later post-Glacial 

sands, so that the relations of the Hinsdale limestones to the Cambrian 

deposits to the west can not be determined

The most westerly outcrop of the Hinsdale limestone is the great 

mass on the south side of the brook just east of the hotel. This is not 

certainly in place, but the great size of the outcrop and the direction of 

the glacial movements make it probable that it is in place here or still 

farther west.

Thirty rods farther west is an occurrence of the limestone in the 

fouiidation of a dam. Under the building and near the water wheel it 

is associated with great masses of the Stockbridge limestone, and this 

is probably the locality cited by Professor Dana 1 as a place where the 

two limestones could be seen in contact.

As the Stockbridge limestones dip in three different ways, they are 

probably bowlders, and from the outcrops to the west it is more probable that the Cheshire quartzite intervenes across the valley mouth, 

separating the two limestones from each other, as is represented upon 

the map.

Thirty rods east of the hotel a road runs north onto the mountain, 

and beyond the single house by the field road leading to the top of the 

clearing mauy outcrops appear in the wall at about the 1,400-foot contour. Above the northeastern corner of the east field is a cliff with a 

fine spring at its foot. For several feet from the base of the cliff the 

rock is the warty, impure limestone carrying chondrodite and green 

actinolite. It grades above into zigzagged strata of white, coarse, 

micaless, granitoid gneiss containing layers and wisps of green actiuolite. These beds are together about 15 feet thick and grade upward 

into a fine-grained, flat-bedded gneiss much like the Cambrian gneiss. 

It is the transition to the Lee gneiss.

The great bowlders of the coarse limestone are very abundant for 2 

miles up the Bast Lee Valley, to the point where the brook crosses the 

road to run north, but outcrops rarely appear.

The presence of these bowlders, the continuance of the bordering 

Lee gneiss in. the hillside north and south, and the deep, continuous 

valley form the ground for believing that the limestone continues along 

the bottom of the valley.

Qnose Pond limestone. The limestone is almost wholly buried beneath 

the waters of the ponds, and the barren, stretched Tyringham gneiss 

appears in the heavily wooded and till-covered banks. In several

1 On Toconic Books and Stratigraphy: Am. Jour. Soi., 3d series, Vol. XXIX, 1885, p! 205.
52 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

places the coarse chondrodite-limestones and the coarse pyroxene rock 

which replaces them form the shore, notably at Elwells Kocks, on the 

south side of Long Pond toward its eastern end. The superjacent 

hornblendic Lee gneisses appear in force at the end of the blind road 

south of Greenwater Pond.

Sop Broolc limestone. Starting 20 rods above the dam, at the 

small village of Sodom at the head of the Tyringham Valley, the bottom and steep banks of the brook show ledges and large bowlders of a 

coarse limestone which is more often a coarse-grained aggregate of 

silicates, both anhydrous and hydrous. Around the village of Sodom 

itself and at the .foot of the steep cliffs farther east many large blocks 

of the same rock appear, which seem to have been brought down by 

the torrents of the brook, as they lie far north of the pre-Cambrian 

outcrops in a direction opposite to the trend of the ice in this region.

At the entrance to the road that leads to Sodom stands the house of 

Mr. Daniel Clark, whose splendid collection of minerals from the valley 

and large store of knowledge of the mineralogy of the country will be 

placed at the service of any student.

The outcrops are mostly concealed in the steep, moss-covered banks 

of the mountain brook, and they have been exploited at much expense 

by Mr. Clark. I spent several days studying his collections, and the 

special peculiarities of the minerals which occur here are described in 

the mineral lexicon appended (pp. 103-127).

The masses of white, granular quartz - calcite mixture, with small 

amount of green pyroxene, titanite, and tourmaline from the altered 

limestone, are catalogued by President Hitchcock as "augitic gneiss 

from Lee and Washington," in catalogue of Massachusetts collection, 

under gneiss, 92 to 95. 1

"Mortised rocfc" of Tyringham. At Tyringham quartz pseudomorph 

after plagioclase is found, penetrated by square- cavities from which 

salite has been removed. (See Pis. II, III.) In these most remarkable specimens great masses of clear, vein quartz are penetrated by 

square cavities from which large crystals of salite have been dissolved, 

while the quartz proves to be pseudomorph after large masses of 

plagioclase, presumably albite.

The replacement is so delicately perfect that the twin structure is 

perfectly-preserved, exactly as in cleavage surfaces of albite. This 

twin striation appears over large areas and is absent over other large 

areas, and the alternation occurs both in the direction of and at right 

angles to the striation.

Moreover, the pearly luster of the 0 (001) face is perfectly reproduced 

in the fractured surface of the quartz, showing that the replacement 

has preserved the structure of the albite, on which the pearly. luster 

depends; that is, repeated separation along the cleavage planes and

1 Kept, of Mass. Board of Agric., Appendix, 1856, p. 51.
U S GEOLOGICAL SURVEY BULLETIN NO. 159 PL. U

MORTISED ROCK; QUARTZ PSEUDOMORPH AFTER ALBITE, CONTAINING CAVITIES OF 

SAUTE CRYSTALS; TYRINGHAM.
U S. GEOLOGICAL SURVEY

MORTISED ROCK; QUARTZ PSEUDOMORPH AFTER ALBITE, SHOWING TWIN 

STRIATION AND PEARLY LUSTER, WITH CAVITIES FROM WHICH SALITE 

CRYSTALS HAVE BEEN REMOVED; TYRINGHAM.
"MORTISED ROCK" OF TYRINGHAM. 53

the formation of air-filled interspaces which have the effect of Newton's 

rings.

Many of the quartz fragments split into large, acute, wedge-shaped 

pieces, which are aggregated in alternate arrangement of the separate 

wedges exactly like the Clevelandite variety of albite from the tourmaline-pegmatite veins.

The Tyringham specimens present an interesting and complete series, 

showing the alteration and disappearance of the pyroxeue. There are, 

first, masses in which the long, white, four-sided prisms of salite, sometimes slightly truncated at the edge and distinctly striated on some 

faces, are from a half to a quarter inch in thickness and several inches 

long, loosely aggregated, and passing into a compact salite rock.

There, are other specimens in which the same white prisms are inclosed 

in white or smoky quartz. They show the very strong basal parting of 

salite, and are often an inch across. They can be seen to be in some 

places wholly or partly replaced by a secondary tremolite or pale-green 

actinolite, and the quartz shows distinct traces of the tabular form 

and the twin striation of albite.

In other specimens the whole or almost the whole of the salite is dissolved, and the cavities take sharp casts of the longitudinal striation 

of the crystals as well as of the transverse partings which cross the 

cavity with the proper obliquity of the basal section of salite.

These specimens were found at Sodom, in the upper end of the Tyringham Valley, in the pre-Oambrian limestone. I was therefore greatly 

surprised to receive from a student a large specimen of the same 

cavernous quartz, which was found by his father, Mr. Charles T. Barker, 

during the digging of the cellar under the Berkshire Life Insurance 

Building in. Pittsfield. It is a wholly unworn block 6 inches on a side. 

The angular faces look as if they might have been broken artificially, 

and the weathered surface of the block suggested that it had been 

buried many years. It is full of cavities, some of which are an inch 

across and 6 inches long. A. 6-inch surface shows over half its area a 

fine representation of the albite cleavage, and half the rest has the 

appearance of the pearly feldspar cleavage; yet the whole is a clear, 

translucent quartz, from colorless to smoky, and splinters broken off 

from the surface snowing striation displayed the perfect optical figure 

of quartz very obliquely placed. I can not imagine that the specimen 

was brought to its present place by ice, for the proof of its pre-Cambrian origin is quite complete and there is no pre-Cambrian limestone 

area to the northwest.

From the interest which these mortised stones have created in the past 

I imagine that the specimen may have come from the Tyringham Valley 

and have been at some time a part of a collection in Pittsfield, as the 

place where it was found adjoins the former habitation of the Berkshire 

Historical Society. This is the specimen figured in PI. III. Mr. Daniel 

Clark, who has collected most of the specimens upon which the fore-
54 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BOLL. 159.

going description was based, has written me as follows concerning the 

Pittsfield specimen:

The specimens have never been found except as drift. I have never seen any 

ledge, but they occur in numerous specimens from small size to several tons. They 

could not have drifted far, for they were angular and showed no signs of erosion, 

and were found on a few acres in Sodom.

The specimen which Mr. Barker found in Pittsfield I believe to be from this 

locality. Over forty years ago Mr. Stephen Reed, of Pittsfield, who was interested 

in minerals, visited my place, and I gave him several1 specimens of what we then 

called mortised rock, and I believe your specimen from Pittsfield is one of those 

Mr. Reed carried from here at that time. I have never known of any specimens 

being found in Berkshire County except in this locality.

Metamorphosis of the pre-Cambrian limestone and paragenesis of the 

limestone minerals. The following tabular statement, derived from 

study of the Hop Brook and Otis limestones, may make clear the probable steps by which the rich mineral beds along Hop Brook have been 

formed. That this has been along a line of faulting has had much to 

do with the complexity of the result. A detailed description of all the 

minerals mentioned is given later:

First stage: A fragmental limestone.

Result of vital forces and transportation. The bed was at first presumably an 

accumulation of animal remains ................................ First calcite

Second stage: A crystalline limestone.

Result of circulating carbonated waters with heat and pressure. In its leastchanged state the bed is now always highly crystalline has recrystallized 

many times in every part . ......-.-*..... ........... ..^....... ....Second calcite

Third stage:

(a) East Lee facies. Chondrodite-phlogopite-limestone, with much clinochlore,

coccolite, and graphite.

Result of circulation of heated waters carrying silica and fluorine. Characterized by very basic magnesian fluosilicates. 

(fc) Otis facies. Pyroxene-wernerite-titanite limestone.

Result of more intense dynamic and thermal activity along fault planes and 

the circulation through the limestone of heated waters containing fluorine, 

chlorine, and titanium compounds.

Characterized by graphite, green and white pyroxene, stout black hornblende, great blocks of wernerite and chalcedony, opalescent orthoclase 

(loxoclase), albite in great masses inclosing salite and calcite-, and pink, 

white, and gray calcite in coarse crystals ...... .............Third calcite

(o) New Marlboro-Norfolk facies. A limestone containing the minerals of b with

wernerite replaced by spinel and nickeliferoua pyrrhotite. 

Characterized by abundant aluminous silicates/ which may perhaps be 

derived, from clayey limestones, while the chlorine may come from the 

ancient sea in which the sediments gathered, and the graphite from the 

organic remains. The abundant titanite was probably brought into the 

limestone from without, and this makes it possible that the^same may be 

true of the alumina silicates. 

Fourth stage: The mortised rock (a). .

Extensivepseudomorphic replacement of albite by quartz (see Pis. II, III) without affecting the inclosed salite; resorption of salite for the formation of 

actinolite, which incrusts the remnant of the salite.

Result of continued action of silica solutions nnder changing conditions of heat 

and pressure.
KMBRBON.] SANDISFIELD AilEA. 55

Fifth stage: Quartz inclosing actinolite.

Extensive development of large biotite crystals in veins in which the crystals 

are greatly crumpled by later movements on the fault. Result of silica solutions at lower temperature. 

Sixth stage: Zeolitization.

Formation of acolecite by the decomposition of wernerite. The formation of

actinolite continues. 

Seventh stage: Zeolitization, continued.

Development on the earlier scolecite of heulaiidite, stilbite, scolecite, laumontite, 

and calcite. Formation of jasper inclosing fragments of earlier silicates. 

Kesult of warm waters and long time.......................... Fourth calcite

Eighth stage: Decomposition and hydration.

Jefferisite from biotite, kaolin from feldspar; solution of calcite and etching of 

crystal faces. Formation of chalcedony inclosing jasper. Effect of atmospheric waters and moderate temperature.

SANDISFIELD AREA.

The long and peculiarly shaped area of pre-Oambrian rocks lying 

south of the Otis area and the extension of the Tyringhain fault down 

the valley of Clam River and across Sandisfield and Colebrook, is composed almost wholly of the upper member of the series the Washington gneiss.

In the center of the southern lobe only, where it is widest, is there a 

trace of the green pyroxene-hornblende rocks, usually associated with 

the Hinsdale limestone. The most striking occurrence within the area 

denned above is found at the northwest corner, in the pasture opposite 

the house of the mineralogist, Mr. D. Clark, at the head of the Tyringhain Valley. In the western part of the pasture the white Cambrian 

gneiss abuts uuconformably against the pre-Cainbrian gneiss. The 

blue-quartz gneiss near the house is so full of allanite and its decomposition products that often a dozen crystals appear in a single hand 

specimen. In tracing these gneisses down from the north this has been 

found to be characteristic for a long distance. Allanite does not appear 

much farther south, but is replaced by fibrolite.

Along the west boundary, 2 miles south of Mr. D. Clark's, at a point 

a mile west of West Otis, just where the boundary line cuts the line of 

long. 73° 10', is a beautiful unconformable contact of the Becket gneiss 

on heavy beds of chondrodite-clinochlore-limestone, which is very pyroxenic and has a broad border of green pyroxenite. It is a mediumgrained white marble, banded in places by black ore, and occurs in 

sufficient quantity to suggest a possible quarry stone.

The hill 1£ miles south by west of Sandisfield, which forms the apex 

of the pre-Cambrian lobe extending northwest from South Sandisfield, 

presents peculiar conditions. In the hollow of the north foot of the hill 

(south of the road) is a typical Cambrian quartzite, at first massive, 

then, three rods south, banded granular, with magnetite grains, which 

further south grades into typical Becket gneiss. Two or t'hree rods south 

of this, in the north foot of the hill, is a 6-foot band of white fibrolitegneiss, which is continuous with the coarse, crushed Washington gneiss
56 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BULU 159.

and impregnated with a coarse feldspathic pegmatite in veins and 

irregular masses.

All along the tortuous boundary the limit of the Washington gneiss 

can be fixed by the presence of graphite and fibrolite in a two:mica 

rusty gneiss, and over the whole area the same characteristics exist, 

although there are many bands from which pieces much like the Becket 

gneiss can be taken.

A mile south of South Sandisfield, near a watering trough, a black 

pyritous quartzite occurs, which is like that above the limestone in the 

East Lee Yalley.

At the southern apex of this area a pale-pink garnet is abundant and 

of large size. The regular intergrowth of inuscovite and biotite is quite 

characteristic.

Bands of black hornblende-gneiss and green pyroxenite occur just 

north of the State line in Sandisfield, south of A. Ducharne's house. 

This rock is rather bright-green, finely granular, and passes into a light 

granular quartzite made up almost wholly of cuboidal grains of brightgreen pyroxene, with distinct dichroism to pale-brown in basal sections 

and with very "coarse prismatic or pinacoidal cleavage. Some grains are 

centrally darker in color and full of dark ore grains. There are a few 

grains of orthoclase, plagioclase, biotite, a green mineral like epidote, 

and a deep-green actinolite. This rock contains no calcite, but it is 

clearly one of the derivatives of the limestone and is changing into an 

amphibolite.

In one instance, in the neck that connects Seymour Mountain with a 

rocky spur projecting southwest, distinct pseudoconglomerate structure appears in the graphitic gneiss. The same rock composes the 

whole top of the hill west of Seymour Mountain.

Above the 1,600-foot contour the entire hill is composed of coarse, 

warty, very micaceous gneiss, with rusty, coarse, sandy grained mass. 

The nodules are about the size and shape of pecan nuts and consist 

of coarse blades of overlapping inuscovite arid biotite, often with more 

or less dark gray from spots of radiated fibrolite. They are first orthoclase, then muscovite, then fibrolite.

The contacts can be well seen at the bridge over Buck River, a mile 

above West New Boston. The first reefs below the bridge are of 

Washington graphitic gneiss. Six rods farther is the contact with the 

thin:banded Cambrian gneiss. The contact is exposed again where 

the rock crosses the two roads northwest of Seymour Mountain, on 

the mountain itself and on its southeast spur, as given above, and 

where it crosses the brook east of Mount Pisgah, on the south line of 

the quadrangle.

OTIS AREA.

This area is cut off on the south side by the Tyringham Valley fault, 

which is continued down the valley of Clam River; on the north side 

it is bounded by the East Lee Yalley fault, which follows the bed of
EMERSON.] « OTIS AREA. 57

Farmington Eiver. Between these two faults there is a central band 

of Hinsdale limestone and its derivatives, flanked on either side by the 

rusty blue-quartz gneiss.

On the west, at the north foot of Filley Mountain, fibrolite begins to 

appear, and ultimately replaces the blue quartz farther south. Ou the 

top of the mountain the two occur together, but the blue quartz can 

not be traced much farther south as an important constituent.

The eastern boundary seems to coincide with the Farrnington Eiver, 

and the first outcrops to the east, in the high banks, are of the Cambrian white gneiss, until, in the bluffs across the brook south of the 

blind road at P. Davison's, there is, at an old mine said to have been 

worked to a depth of 10 to 15 feet, an apparent outcrop of a pyritous 

weruerite rock of pre-Oainbrian age. It seems to lie a little west of the 

bluffs of white gneiss.

The boundary then runs southwest into Sandisfield, and at the south 

foot of the hill, 40 rods west of H. S. Hawley's, the last house before 

turning off to Cold Spring, is another old mine. A deep trench runs into 

the hill where the white gneiss on the east and the rusty, graphitic, 

.pyritous gneiss full of garnets and black hornblende (this is the ore) 

on the west are closely approximated.

The next point where the two can be seen to approach each other is 

on the hill west of the south end of Spectacle Pond, in Sandisfield. 

The apex of the hill north of an abandoned house is of the white gneiss, 

standing nearly vertical, with the strike shifting from north around to 

west, in great folds, from the influence of the fault to the south.

The western boundary is normal. The rusty gneiss rests against the 

white gneiss and is overturned to the west.

The boundary of the pre-Cambrian on the Cambrian is carried, both 

on the northwest and on the southeast, directly across the strike of the 

two, while whenever the two are found in immediate contact they are 

squeezed into superficial conformity. This is because of the lack of 

sufficient outcrop. If one could trace the whole boundary, I have no 

doubt it would run northeast in general direction, but with many sharp 

serratures directed northwest and southeast.

The bottom of the Farmiugton Eiver Valley in Otis abounds in 

large bowlders containing, in great abundance and often in very fine 

crystallization, the following minerals: wernerite in white stout crystals 

and large lavender masses, pale-green pyroxene in cleavage masses 

several inches across, titanite, hornblende, emerald-green actinolite, 

pyrite, and graphite.

On the hill a half mile south of the hotel is an outcrop of coarse, 

granular, scarcely cemented limestone, carrying red-brown titanite and 

grains of wernerite and coccolite, deeply excavated by weathering, 

from which, tradition says, two cart loads were once blown out by a 

mysterious explosion while the owner of the farm was in close proximity 

to the place.
58 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BULL. 150.

Along the river in Otis Center there are also found many large 

bowlders of a fine chalcedony, a very characteristic fault rock which 

gives evidence of the special activity of circulating solutions along the 

fault plane. There are, among others, very large masses of fine, white 

to pale sky-blue bowlders, which are drusy and botryoidal in cavities. 

They represent the last stage of deposition, since they inclose many 

angular fragments of a deep-yellow jasper, showing that this jasper had 

been an earlier filling of the fissure, made, doubtless, by waters at a 

higher temperature, which were able to dissolve iron as well as silica 

from the gneiss.

Both these chalcedonies contain fragments of the wernerite, proving 

that still earlier movements had shattered the wernerite limestone, 

that a solution of the calcite had followed, and that, later, a. cementation of the residual silicates by silica had taken place.

"SNOWPLOW" ANTICLINE OF BEAR 1 MOUNTAIN.

"Beartown Mountain. The vast pile of mountains that bears this 

frightful name lies southeast of Stockbridge." (Hitchcock's Final 

Report, p. 235.)

The great anticline of Sky Hill and Bear Mountain has been closely 

folded, with north-south axis, has been strongly overturned to the 

westward, and has then been bent around into a sharp V (with apex 

directed northwesterly), by .the movement of the north limb of the anticline around through the east quadrant so as to point southeast. It is, 

of course, not intimated that these events happened successively, 

though it does not seem to me wholly impossible that such may have 

been to some extent the case. It- is certainly most probable that they 

were nearly contemporaneous.

As a result of this posture of the rocks, the high ground, consisting 

of older rocks, encroaches on the limestone valley to the west by 

exactly the full width of this anticline. The general structure of the 

anticline can well be compared to one of the large double railroad 

snowplows formed of two vertical concave surfaces which diverge from 

a central prow. If the Cambrian gneiss on the north and west of the 

pre-Carnbrian could be removed, the north and west surface of the preCambrian would have the shape of such a snowplow. In other words, 

northeast and southwest sections across the mass present a gradually 

widening fan-structure as they are drawn along lines more and more 

distant from the apex at the northwest.

The same structure is continued for many miles to the southeast, and 

1 mile south of Monterey the Cambrian conglomerate-gneiss mounts 

over the Stockbridge limestone in a similar suowplow anticline and is 

itself surmounted in the same way by the pre-Cainbrian of Morley Hill.

The area of exposure of the pre-Cambrian in Bear Mountain is 

lunate; a narrow band extends from the apex down the crest of the

1 See footnote on p. 13.
EMERSON.] "SNOWPLOW" ANTICLINE OF BEAR MOUNTAIN. 59

mountain from its northern end for 4 miles south, bends east, with 

an easy sickle-shape, and ends just across the road north of Livermore 

Hill.

The west lobe has an average width of less than a half mile. From 

its northern part it sends a broad lobe, a mile wide, east for 3 miles into 

the Sandisfield quadrangle. The western lobe is composed of the Washington blue-quartz gneiss, often strongly banded, graphitic, and very 

rusty. The eastern lobe, excepting its eastern end on Sky Hill, which 

is described below, is composed of the coarse, white, liguiform Tyringham gneiss.

A band of black amphibolite, of fine grain and well bedded, which 

occurs at or near the contact but within the Becket gneiss, aids in 

fixing the limits of the older bed.

The structure of the western lobe is that of a closely compressed anticline overturned to the west. Its axial plane strikes a little west -of 

north for three-fourths of its length and bends around to strike southeast in its southern fourth; it dips 75° to 80° E. The best places tostudy the beds are where the road crosses Bear Mountain on its south 

end a mile nortli of Livermore Hill, and on the top of Sky Hill. At 

the former place the axis of the fold is exposed in a heavy bluff on 

the east of the road south of a coal-burner's hut, and is a coarse, very 

qnartzose biotite gneiss, quite rusty and well banded, and composed 

almost wholly of blue quartz.

Fifty rods to the south the amphibolite crosses the road and fixes the 

boundary. Fifty rods north, at the highest ground south of the last 

bridge over the brook, the white Cambrian gneiss can be seen in contact with the blue-quartz gneiss, dipping away from it, with many 

convolutions, to the northeast.

The bed of amphibolite crosses the brook opposite the schoolhouse a 

mile east of Bear Mountain peak, and appears in great force threefourths of a mile southwest of that point and 100 rods southeast of the 

peak, where it has a width of 40 rods. From the schoolhouse it bends 

east and runs down the Monterey road to the boundary of that town.

The boundary of the bed continues along near the road, often marked 

by small hornbleudic bands.

At the isolated home of Mr. Beebe, the well-known weather prophet 

of the inountain;. the amphibolite again appears, while south of that 

point, in a section a mile long crossing the whole band from north to 

south and emerging near the beginning of the Monterey road, only the 

monotonous Tyringham gneiss is visible.

At the east end of the syncliue is Sky Hill, rising above the former 

settlement of the Shakers, at Fernside, and noted as the burial place 

of Mother Ann, queen of the Shakers.

An area nearly a mile long and a third of a mile wide, upon the crest 

of the hill, is occupied by the rusty graphitic Washington gneiss, while 

the white Cambrian gneiss wraps round the two kinds of pre-Cambrian 

rocks, showing unconformity.
60 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

A bed of coarse gneiss, with a band rich in hornblende and titanite, 

is the southeastern apex of the pre-Cambrian rocks. Everything indicates an overturned anticline of the older rocks included in the Cambrian Becket gneiss.

The Becket gneiss is abundantly exposed over broad areas to the 

east and north, and strikes K 20 to 30° W. aud dips 30 to 40° W. 

under the pre-Oambrian. On the eastern slope of the east spur of Sky 

Hill the Becket gneiss rests, wavy and irregular, on the older rock, 

which is a stretched gneiss of light color with large grains of magnetite.

At the top and at the east aspect of this hill the typical rusty, bluequartz, graphitic gneiss is in great force a ragged-surfaced, wellbanded, rusty-brown rock.

The bedding is expressed by bands almost an inch apart, which, 

being more quartzose, stand at a regular uniform level, while the intervening micaceous layers are deeply excavated by weathering, making 

a very rough surface. The rock is always very rusty, and at times 

. shows an abundance of lavender quartz, but is usually so crushed that 

only a blue core can be seen here and there.

The boundary is beautifully exposed around the north slope of this 

east spur, and runs 5 rods south of two great dead trees which are visible from the whole length of Tyringham Valley below. It then runs 

northwest, past a large cellar of the abandoned Shaker settlement at 

the 1,700-foot contour northwest of the summit of Sky Hill.

All of Sky Hill for 100 feet down is of the same rusty rock. A 

great band of black, heavy, hornblende rock runs across the crest of the 

hill, and west of it is a micaless gneiss with the aspect of a quartzite. 

A hundred feet down the slope on the west is a very rusty, extremely 

graphitic schistose gneiss. All these beds are pre-Cambrian.'

Going down the mountain to Fernside we pass over the whole Cambrian and Silurian series inverted, and then over the Silurian and Cambrian in normal order, and come upon the pre Cambrian in the bottom 

of the valley. In order to understand this complex syncline one should 

consult the sections of Bear Mountain in the Housatonic folio.

MONTEREY AREA.

As a result of strong overthrusts to the west a small pre-Cambrian 

area appears on the south line of Monterey, between two brooks. Its 

south end is in New Marlboro, at the brook which crosses near the 

house formerly occupied by E. R. Smith, 2£ miles south of Monterey. 

. Here the section in fig.'10 is exposed. Beneath the dam the Becket 

gneiss is in place, with traces of pebbles 1 to 5 inches long. This 

gneiss is continuous in the field northeast of the house, and contains the 

beds of amphibolite which mark the neighborhood of the Cambrian 

contact. The rock dips northeast and seems conformable with graphitic gneiss, which appears in the yard of the house and can be traced 

into the great hill of pre-Cambrian rocks to the north. It is o verthrust
EMERSON.] MONTEREY AREA. 61

onto the Stockbridge limestone, which appears in great force west of 

the house and to the south grades into mica-schist.

On the hill to the north the blue-quartz gneiss is abundant, associated with coarse graphitic gneiss. Coarse black hornblende in large 

cleavage pieces, rusting to red in the center, and a dark-green pyroxenic rock with remnant of limestone, also occur here.

All along 'the northwestern border is a sugary crushed rock, almost 

wholly fine granular plagioclase, with a uniform small amount of magnetite, and at times minute garnets, a little biotite^ and films of muscovite. 

It carries also lenses of deep-green to black coarse hornblende, with 

centers of the coarse calcite from which the silicate has been derived. 

The whole is a crushed fades of the pre-Cambrian limestone on the fault.

-Cb Ss Aw -Cb 

.FlG. 10. Overtlirust of pre-Carnbrian on Stockbridgo limestone; north line of Now Alarlboro. 

Gb, Becket gneiss; Ss, Stockbridge limestone; Aw, Washington gneiss.

SOUTHERN AREAS.

The small pre-Cambrian outcrops which run south from New Marlboro 

village to the southern line of the town are everywhere very rusty and 

have often tempted the landowners to unremuuerative mining, as at 

the Cleveland, Hotchkiss, and Wads worth mines. Bands of impure 

limestone are abundant and have often been changed, more or less, to 

silicates. Calcareous amphibolites and pyroxenites are as a result 

common, and often carry a nickeliferous pyrrhotite, which at the Hotchkiss mine has furnished fine crystals.

The limestones are characterized by the abundance of sulphides of 

iron and by the absence of the finely crystallized silicates, of wernerite, 

and of various forms of chalcedony, which appear farther north, where 

the beds are cut by great faults.

The pre-Cambrian rocks lie in whole or in part in deep landlocked 

depressions, which seem to have been formed by the removal of the 

limestone by solution, the sinking in of the thin, flat Cambrian cover 

and the later removal of its fragments. The last stages of this work 

of removal we may ascribe to the action of the Glacial ice.

NEW MARLBORO AKKA.

A mile southwest by south of Southfield, at the house of G. Lawrence, the Becket gneiss, with a band of black hornblende-gneiss, 

crosses the road.

A few rods north are large cliffs of the rusty, very graphitic gneiss,
62 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

with pale-green hornblende, and the boundary can be followed from 

there N. 60° W., making a sharp loop where it crosses the border of 

the quadrangle and then going northwest over the north flank of the hill, 

passing thus into the Sheffield quadrangle. It again enters the Sandisfield quadrangle on Oollins Hill, where the Cambrian gneiss is beautifully conglomeratic, 1 and runs along just south of the road into New 

Marlboro and through the village to a point near a smalKdarn east of 

the town.

On Collins Hill the pre-Oambrian gneiss contains the blue quartz 

which is so characteristic farther north.

AREA SOUTHEAST OF SOUTHFIELD.

High bluffs of the light Becket gneiss rise north of the house of J. 

Wade and occupy the hill to the south of it, and between emerges a 

small pre-Cambrian area, mainly in the valley bottom, but rising a little 

above it a short distance west of the house. This area is a flat triangle 

about 100 rods long and 40 rods wide, and along its northeast border 

rises a band of coarse, impure limestone and pale-green hornblendegneiss.

HARMON POND AREA.

The banks on the east side of this pond descend almost vertically 

into deep water, and 3 feet above the water's edge the pre-Cainbrian 

emerges from beneath the Becket gneiss as a band of green amphibolite 

with a thin baud of coarse, loose, granular, coccolite-chondrodite-limestone, and a micaless gneiss with titanite and chlorite pseudomorph, 

apparently after titanite. Bowlders of the pre-Cambrian rocks are found 

around the pond, but the first outcrops in the bluffs back from the 

water are Cambrian. (See section of Cleveland Mountain shown in 

fig. 11, p. 64.)

SOUTHFIELD CEMETERY AREA.

A little way up the hill from the Southfield cemetery, a mile south of 

the village, is a ledge by the roadside where the extremely rusty character of the rock has tempted somebody to waste time in blasting, and 

the ledge has been so undermined that the rock can be seen to form alow dome. Outcrops of the Becket gneiss are near at hand on all sides, 

showing that it is a very limited area domed up through the newer 

rock, which is an exceedingly rusty dark-green pyroxenite, largely 

horublendic.

HOTCHK1SS AREA.

Northwest of East Pond in New Marlboro, a few rods north of the 

house of Mr. I. Hotchkiss, a bed of massive, white, coarse limestone 

emerges from beneath the Becket gneiss, which is at this point a fine 

quarry granite, and a limekiln has been erected here. The limestone 

dips 25° N. on the north side of the quarry and 20° S. on the south side.

1 My attention was called to the locality by Prof. William H. Hobbs.
RMERSON.] SOUTHERN AREA. 63

It is exposed with a thickness of 10 feet, and no bottom appears. It 

is exceptionally pure; a few small cbrondrodite grains and pale-green 

chlorite flakes occur.

At the edge of the brook, a half mile below the house, a shaft has 

. been sunk about 12 feet upon a group of small pyrite veins in the 

coarse, rusty, dark-green pyroxenite. Crystals of pyroxene an inch 

across can be found, generally eight-sided prisms, terminated by imperfect and rounded O faces. A coarse bladed green hornblende also 

occurs. Two veins of the pyrite are 3 to 4 inches wide, bunching to a 

foot and showing rude cubes of pyrite 1 to 1£ inches.across, and pyrrhotite in cubical masses up to an inch on a side and in fine crystals 

an inch long three-sided, slightly tapering prisms with edges truncated. These crystals weather to a liver brown; a basal cleavage 

develops, and the layers warp apart and spoil the crystals.

Albite occurs in druses of many-faced crystals, with beautiful play 

of color on the o> P oo (010) faces. On. the dumps everything is coated 

with a crust of a colorless sulphate.

CLEVELAND AREA.

This is a triangular area 1 mile long from east to west, a half mile 

wide from north to south, half on the Sheffield quadrangle and half on 

the Sandisfield quadrangle.

At its northern apex is the Cleveland iron mine, about 100 rods northeast of the house of J. Cleveland. The Becket gneiss, somewhat granitoid, rests nearly horizontally upon the Hinsdale limestone, which is 

4 or 5 feet thick, and below this, in the hillside, is a great thickness of 

the coarse, light-colored Hinsdale gneiss, in which is an irregular vein 

of magnetite, bunching in places to a foot in width.

The limestone is a white, firm, coarse-grained rock, in most of its 

thickness showing only a few pale-green mica scales. Some layers 

are filled with green mica, buff phlogopite, deep-red chondrodite, and 

colorless tremolite in fine needles.

Commencing about 10 feet below the limestone the gneiss is extensively trenched to open the iron ore. The most abundant variety is a 

clear gray gneiss, much resembling at first sight the Becket gneiss 

above the limestone. It is darker gray, firmer, and the black mineral 

is sometimes wholly black granular hornblende in rounded separate 

grains with fused surfaces, very different from the same mineral in the 

black Cambrian gneisses. In other places the black mineral is wholly 

magnetite. Much of the gneiss is highly stretched, the very scanty 

dark mineral being a dark-green hornb]endev or epidote and hornblende.'

Along the magnetite vein the rock is greatly crushed. The purest 

magnetite is mixed with hornblende, and the folia of the Avhite gneiss 

inclose rows of large hornblende nodules and masses of epidote and 

contain druses of albite crystals in cavities.

Coarse, friable, granular limestone, containing many small grains of
64 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BOTJ.. 159

dark-green hornblende and pistachio-green pyroxene, are caught up in 

the crumpled rock (see fig. 11) or intergrown with the white hornblendic gneiss. This is very different in texture and accessories from 

the compact thick-bedded chondrodite-limestone above. It can best be 

looked upon as a calcareous vein stone derived from the normal interbedded chondrodite-limestoue.

The contact may b.e seen in the edge of the woods north of the house 

of J. Oanfield, nearly 1 mile southeast of the Cleveland house, just at 

the west edge of the long bluffs of contorted Becket gneiss which 

border the road on the north for a long way east of this house. The 

biotite-gneiss changes suddenly into the coarse hornblendic gneiss. 

The boundary turns sharply west at this point and must closely follow 

the road west,'as the outcrops of the biotite-gneiss are abundant on the 

south side of the road past the southern end of the Cleveland road to 

the vicinity of the Wadsworth mine, 100 rods north and 10° east of the 

house of Mrs. J. P. Wadsworth. Here are two openings, 10 feet deep, 

upon a rusting bed of calcareous actinolite-schist. A former limestone 

bed has been almost wholly changed into balls of a granular grassgreen hornblendebiotite mixture. The 

limestone is pinched 

into the gneiss in a 

remarkable way, and 

where it is changed 

into hornblende 

rock it could be mistaken for an altered 

dike.

In the center of the area is the Cleveland mine proper a shaft about 

20 feet deep. The rock is a deep-green massive pyroxene-hornblende, 

carrying much pyrrhotite and a little chalcopyrite, considerable coarse 

granular calcite, and graphite. The mine was first opened as a gold 

mine, and I was shown a nugget of gold half as large as a pea and one 

of silver as large, as a dollar, which were said by the owner of the 

mine to have been obtained from a barrel of the ore (500 pounds). The 

assay was made by a Boston firm. An assay made by Arno & Co., 

Cedar street, New York, gave $5.50 gold and $0.75 in silver for 500 

pounds. Later assays have shown no precious metals but varying 

quantities of nickel from 3 to 26 per cent. This information was 

given me by Mr. Cleveland. The bed was being worked in 1891 by a 

New York firm as a nickel mine.

The structure of the Cleveland area is anticlinal. The axis is N. 35° 

W., and the whole is overturned to the west, so that at the northern 

end, where the overturn is complete, the Becket gneiss rests almost 

horizontally on the Hinsdale limestone and gneiss. On the southern 

end they stand almost vertically. Along the southwestern side the

FIG. 11. Limestone pinched into pro-Cambrian gneiss, Cleveland 

mine, New Marlboro.
EMERSON.] NORTH CANAAN AND WEST NORFOLK AREAS. 65

FIG. 12. Overturned anticline in Cleveland Mountain, west of HarmonPond, NewMarlboro. Cb, Becket gneiss; Aw, Washington 

gneiss; Ss, Stockbridge limestone.

Becket gneiss dips low beneath the older rock and is inverted. Still 

farther west and lower down the Cheshire quartzite rests on the Stockbridge limestone in the beautiful dome cited by Professor Dana; ! so that 

going west from the Cleveland mine one has the whole' series, from the 

pre-Cambrian to the 

limestone inverted, 

as indicated by fig. 

12, showing section 

through the Cleveland

mine and through Harmon Pond.

NORTH CANAAN AND WEST 

NORFOLK AREAS.

Limestone. On the 

road from Norfolk that 

enters North Canaan 

at its extreme northeast corner are fine 

ledges of the white 

Cambrian gneiss. 

Crossing the brook 

and going southwest up the hill we find a small wooded [ knoll just 

southeast of the road, which consists of the characteristic schistose 

nodular gneiss of the region, and shows on it* eastern aspect the single 

outcrop of limestone which is found in\the pre-Cambriau of this area.

> It is in the east edge of the 

woods and 10 rods from the 

road, and is exposed only 30 

feet from north to south and a 

few feet in width. Prof. William H. Hobbs blasted into it 

for 8 feet and found it a true 

outcrop. The limestone dips 

50° W. underneath the nodular 

gneiss, while a few feet to the 

east the Cambrian gneiss outcrops in the pasture, striking N. 

20° E. and dipping 70° W. It 

is a coarse granular limestone 

of translucent grains, with 

rotted chondrodite, phlogopite, and large blue orthoclase nodules.

Nodular gneiss. The coarse, rusty, highly micaceous inuscovitebiotite-gneiss adjacent to the limestone described above is full of large 

pebble-like nodules, which represent ancient porphyritic feldspars, now

3.13. Fault contact of pre-Cambrian (Aw) on Cambrian Becket gneiss (Gb) containing granite (g) and 

amphibolite (a); northwest corner of North Canaan.

1 On Taconic Hocks, etc.: Am. Jour. Sci., 3d series, "Vol. XXIX, p. 222. (Locality 14 on Dnna's map.)

Bull. 159- 5
66 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

largely changed to matted masses of coarse muscovite which is filled 

in varying degrees with fibrolite. It also contains large garnets, and 

weathers to a very rough surface.

The rock contains graphite regularly, and is exactly like the rock of 

Seymour Mountain iu Sandisfield, into which I have traced the preCambrian blue-quartz gneiss of Tyringham and Otis. (See p. 56.)

Following the road a half mile southwest, to near its end orfe Tobey 

Hill, we find, south of the red house at the end of the- road, the best 

exposure for the study of these nodular gneisses and their posture 

against the fault by which they touch the; Cambrian on the south (see 

fig. 13).

The white gneiss (Gb), with beds Of amphibolite and garnets, abuts 

against the nodular gneiss, and this rock continues with a monotonous 

regularity for a mile southeast, to the west foot of Ball Mountain, where 

it often carries a little tourmaline.

FIG. 14. Campbell Falls section (central part given in PI.IV), New Marlboro. 6b, Becket gneiss;*

Aw, Washington gneiss.

Campbell Falls section. Following the schistose gneiss a half mile 

northwest from the limestone, to the point where the next road 

north crosses Whiting River (the brook coming from East Pond) at a 

fine waterfall, we find clearly shown the contact of the Cambrian gneiss 

on the east with the older gneiss. Fig. 14 gives the relations of the 

two rocks and PI. IV shows them represented in the central portion 

of the diagram. All to the right or east of the water is Cambrian 

gneiss, which continues a little way to the left, to the foot of the vertical 

bluff of the older nodular gneiss which rises above the upper level of 

the water. The strong shear planes run in the white gneiss parallel 

with the falling waters, and west of the pool, at the bottom, the white 

gneiss can be seen dipping beneath the older rock.

South of the fault the same nodular gneisses appear in force, and one 

of the best places to study them is south of the road running northwest 

onto Tobey Hill from the point mapped in fig. 13 (p. 65) and south 

of the western house in the figure. Specimens from this place have
U. S. GEOLOGICAL SURVEY BULLETIN NO. 159 PL. IV

CAMPBELL FALLS, NEW MARLBORO; LOOKING NORTH.
EMEBSON.] " CAMPBELL FALLS SECTION. 67

been described by Professor Hobbs l as illustrations of the change of 

orthoclase to muscovite.

These rocks cross the railroad at the west end of the long West Norfolk cut. (See P-l. V, p. 76.) Here there is first a rusty, spangled muscovite-gneiss, containing graphite, pyrite, and fibrolite, dipping east 

beneath a light actinolite-garnet-gneiss, which also dips east against a 

granite-filled fault plane near the third telegraph pole from the entrance 

of the cut. It abuts against the black quartzite common at the' base 

of the Cambrian.

The same nodular schist makes up the high ground south of the 

river at West Norfolk and is well represented in the ledges south of 

the hotel in Norfolk.

On the brow of the hill iii West Norfolk, near the south line of the 

Sandisfield quadrangle, iron ore is found around the house of H. M. 

Jones, near the upper end of Lake Wungum.

Nodules in the gneiss. The rock at Campbell Falls is a coarse muscovite-biotite-gneiss, very micaceous, with nodules, about an inch long, 

of coarse peginatitic feldspar, bordered by a band of black biotite and 

brown hornblende. Another form is in its central part made up of a 

single crystalline grain of quartz, with a partial border of coarse, muchtwisted muscovite, both full of fibrolite. Another form is composed of 

a single large crystalline grain of muscovite, full of fibrolite; and still 

another is of coarse granular microcline, without fibrolite.

The groundmass of the rock is a finely foliated mixture of muscovite and biotite, often intergrowu, often much twisted by pressure and 

finely foliated, but without fibrolite.

The rock, as found in the ledge west of the limestone on Tobey Hill 

and in bowlders southeast of Ball Mountain, coming from the same 

.area contains nodules of muscovite full of tufted fibrolite, and large 

grains of orthoclase also containing fibrolite. The nodules are separated by a finer grained, confused rauscovite-biotite groundinass; A 

quartz-feldspar mosaic often surrounds the nodules, being formed by 

their partial crushing.

The fibrolite is found in quartz, feldspar, and muscovite, and not in 

biotite. It is often in a sort of sagenitic network on the C face of the 

mica, arranged parallel to its prism faces.

Prof. William H.Hobbs has described these nodules from the bowlders 

and found the cleavage and Carlsbad twinning suture of the feldspar 

retained in the mica. 1 He gives the following analysis made by Dr. 

W. F. Hillebrand, of the United States Geological Survey.

1 Pseudomorphs after feldspar from Norfolk Township, Connecticut: Am. Geologist, Vol. X, p. 46.
68 GEOLOGY OF EASTERN BERKSHIRE COUNTY, "MASS. [BULL. 159. 

'. Analysix of nodules from Norfolk Township, Connecticut.

'cur*

AlA ...------ .- --- - . -------- --- ------ 

Fe203 ....'..................-...............................'.........

FeO............. .................................................

CaO.... ...................................................... .....

KiO. ..............................................................

Na20 ..............................................................

H20 at 100° .............'.............................."...........'..

TiO, ...............................................................

SrO.- ..............................................................

'Li/) .............'..................................................

p f\

Per cent.

76.32

15.87

.53

.36

.26

4.55

.20

2.01

100.00

We examined the locality together and then considered the nodules 

to have been pebbles, as mentioned in his article, an opinion which I 

have since abandoned.

. . SOUTHEASTERN AREA.

Above Eiverton, on the Farmington River below the Sandisfleld 

quadrangle, is a large outcrop of the Hinsdale limestone and the associated hornblendic and pyroxenic rocks, rising in the center of a broad 

area which may be associated with the Washington gneiss through the 

Sandisfleld area just described, though the blue quartz is absent, being 

replaced by fibrolite, while the presence of graphite and of both micas, 

the rustiness, and the coarse, ragged, somewhat schistose texture of 

the gneisses distinguish them from the Cambrian above.

A characteristic rock in this area is a dull-black biotite-gneiss, highly 

fibrolitic and rusty, spangled with large flakes of muscovite and often 

abounding in large, irregular garnets. The band extends far northeast 

and southwest, but nearly its full width is found in the Sandisfield 

quadrangle. Where it enters the quadrangle, east of Mount Pisgah, 

it is a sugary-crushed, rusty, graphitic hornblende-gneiss.

PYROXENITES AND AMPHIBOLITES.

The passage of the limestone into a coarse-granular leek-green 

pyroxenite is very common; a large bed of this kind appears at A. 

Ducharne's, at the south apex of the Sandisfield pre-Cambrian area. 

(See p. 56.) ' . A knob of a similar rock projects above the level of the track at the 

signal house west of the Middletield station. It is a calcareous diopside 

rock derived from the pre Cambrian limestone and projecting into the 

Becket gneiss. Other similar projections appear in the cut nearer the 

limestone. It has disseminated crystals of a black hornblende, lustermottled (poikilitic) by the earlier diopside, and changes into a green 

amphibolite which contains little plagioclase and no ore.
PYROXENITES AND AMPHIBOLITES. 69

Because of the interest which attaches to the origin of amphibolites, 

special attention is called to the change of the limestone in Hinsdale 

into black, massive amphibolite and hornbleudic gneiss, both by the 

formation of interstratified beds of various dimensions, and by an 

alteration progressing from both the top and the bottom until only a few 

feet of limestone remain at the center, and also to the Cleveland area, 

where the limestone is pinched into the gneiss like a dike and then 

partly changed to amphibolite (fig. 11).

The amphibolite which occurs in continuation of the limestone at 

the Alderman farm at Becket Center and which has been quarried as 

emery and copper ore, and the exactly similar rock found adjacent to 

the Coles Brook limestone 1 mile east of the Alderman farm, are more 

difficult of assignment. This is a black, massive, granular rock quite 

like the altered Cambrian dikes described below. It carries garnet, 

and the black ore which it contains is associated with titanite (leucoxene); the colorless ground is largely quartz. The rock is much like the 

Lee gneiss above East Lee, described on page 33, and I have associated 

it with the Lee gneiss, as a derivative of the calcareous transition beds 

above the Hiusdale limestone.

ANALYSES OP PRE-CAMBRIAN LIMESTONES.

The following analyses of pre-Canibrian limestones are taken from 

Hitchcock's Final Eeport of the Geology of Massachusetts, page 80. 

The other Berkshire analyses in this table are of the Stockbridge 

limestone:

Analyses of pre-Cambrian limestones.

CaC03 .. ...................

MgCO, ....................

Fe2 03 ...... ................

1.

54.80

44.98

.22

100. 00

2.77

2.

56.25

31.56

1.12

11.07

100. 00

2.78

3.

51.66

39.48

.91

7.96

100. 01

2.77

4.

58.31

28.61

.1.24

11.84

100. 00

2.84

1. Lee, 1 mile east of village; burned for lime. This is from the hill above East 

Lee.

2. Middlefield; Coles Brook; white.

3. Blandford; white. This is a great bowlder from the Coles Brook bed, found 

south of the village of North Blandford.

4. Becket, southeast part; magnesian.

CAMBRIAN SYSTEM.

An inspection of the map will show that the Cambrian gneisses and 

quartzites cover more of the surface than do the rocks of any other 

system.

In the area between the pre-Cambrian and the Stockbridge limestone 

it is helpful to carry out the distinction between the lower portion of the 

system the Becket gneiss, which was originally largely conglomeratic 

and is now chiefly a muscovite-gneiss with some quartzite and an
70 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. (BOLL. 159.

upper portion which was 'originally largely a quartz sand and is now 

changed to a more or less micaceous quartzite the Cheshire quartzite, 

very generally characterized by the presence of minute crystals of darkbrown tourmaline, although the quartzite sometimes extends to the 

base of the system.

This quartzite is locally replaced by a mica-schist, which is often 

greatly corrugated. On the east side of the pre-Cambrian the Cambrian 

is largely a biotite-gneiss and is completely gneissoid up to the hydromica-schists and lacking in tourmaline.

UNCONFORMITY AT 'THE BASE OF THE CAMBRIAN CONGLOMERATE.

Five rods east from the mountain cottage on the hill high above Dalton Station the conglomerates, themselves nearly horizontal, can be 

seen resting upon thev vertical beds of the older gneisses which strike 

N. 80° E. One can follow the junction in the cliffs south and then 

for a mile southwest down the mountain side, to the brook above J. S. 

Barton's, with excellent exposure, as indicated in fig. 4, page 40. It continues up the side of Warner (or Day) Mountain, and on south through 

the woods for 2 miles to the great fault described hereafter (p. 92). 

On the opposite side of the anticline, along the east slope of the same 

hill, the same unconformity can be seen, though the outcrops are poorer. 

Everywhere the old gneisses strike N. 80° E. and are nearly or quite 

vertical, while the conglomerates, nearly horizontal at the top, take a 

low dip westward down the west side and eastward down the east side 

of the long hill, and before it was cut through along the crest of the 

hill they mounted over it symmetrically.

The unconformity is thus striking, abundantly exposed, and extends 

for a long distance. The same unconformity clearly exists along the 

west flank of the West Washington anticline (shown well at P. Conroy's house), a mile northwest of the Becket reservoir.

Around the great Hinsdale anticline there is everywhere a general 

apparent conformity, but there is very commonly a discrepancy of 10° 

to 30° in the strike, while the dips uniformly agree in being low to the 

east; but the whole anticline is so forcibly pushed over westwardly and 

flattened, and the outcrops on the exact junction are so few, that it gives 

little important evidence on the subject.

The pre Cambrian at the Coles Brook anticline is thrust very irregularly through the Cambrian, and the unconformity is well shown in the 

description of the section at the mouth of the brook (see p. 41), and 

is apparent in the whole length of the band from the contact of the 

Cambrian gneisses with the different members of the older series. It 

is more beautifully shown a mile north of the railroad cutting, where 

the road comes down off the mountain and crosses the limestone near 

the site of the burned house of H. Hawes. As seen in the figure (fig. 

15), the Cambrian gneiss wraps in easy folds over the vertical preCambrian limestone, which is accompanied by a rusty biotite-muscovite-
EMERSON.] CAMBRIAN SYSTEM. 71

gneiss, with tourmaline aud coarse graphite, and on the top of the hill, 

where the gneiss is worn through, the limestone appears.

A nearly vertical secondary schistose structure is present in much of 

the gneiss. It is a typical Becket gneiss, with many striated octahedra 

of magnetite, aud at the sharp bend in the road it contains an 8-foot 

bed of a fissile black amphibolite with films of biotite. This makes a 

very beautiful slide under the microscope. Around the many grains of 

magnetite an abundant growth of titanite (leucoxene) appears, swelling 

into larger crystals in a limpid ground of untwinned plagioclase grains. 

It is probably an altered eruptive rock.

FIG. 15. Cambrian gneiss folding over pre-Cambrian limestone unconfocmably; Middlefteld. 

CONGLOMERATE.-GNEISS (BEOKET GNEISS).

In the northwestern part of the area the broad band of light-colored 

gneisses which encircle the old blue-quartz gneiss of the Dalton anticline is as uniformly characterized by the abundance of muscovite as 

the older series is by that of biotite. . The latter mineral is not always 

absent in the newer rock, but when it does occur it is in small, scattered flakes, not in connected films.

All the other characteristics of the older series are conspicuously 

absent, except that the blue quartz occurs in grains and pebbles, plainly 

secondary. It passes gradually upward into the Cheshire tourmalinebearing quartzite.

The base of these gneisses is often a heavy bed of the most clearly 

developed conglomerate of quartz pebbles white, black, and blue, 

commonly white, with rarely a pebble of feldspar or gneiss from 5 mm. 

to 100 mm. in length, uniformly well rounded, and all arranged parallel 

to a common plane. They are sometimes apparently flattened parallel to that plane to quite broad sheets, in one case to round-edged plates 

of quartz 150 mm. by 100 mm. by 10 mm. These pebbles are generally 

inclosed in a large quantity of groundmass, which is changed into a
72 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

mica-schist or a micaceous quartzite by the development of more or 

less muscovite, and many tourmaline crystals encrust the surface of the 

pebbles, often in radiating groups.

This conglomerate bed is continuous and can be traced for miles 

across Hinsdale and into Washington. It is best studied at the Daltou 

clubhouse and across to tie south in the open pasture, represented in 

fig. 4 on page 40. The conglomerate is here so beautifully distinct, the 

ground so completely changed to a rnuscovite-schist, and the complete 

unconformity to the underlying pre-Cambrian so well exposed, that this 

is the best locality in Massachusetts for the study of all the relations 

of the two formations.

The growth of rosettes of tourmaline on the pebbles and the shearing of the conglomerate into a complete gneiss along narrow bands, 6 

inches wide and at right angles to the bedding, on either side of which 

the pebbles are but slightly flattened, is especially notable. From the 

clubhouse flat one will do well to follow the contact down the slope to 

the brook (see fig. 4), where the Cambrian and the pre-Cambrian can be 

seen in contact, and also to go across to the east of the pasture, to the 

point indicated in the right-hand part of the figure, where the gneissoid 

development is more complete, although the pebbles are in places quite 

distinct.

From the Hinsdale station one may go a mile north along the railroad, to the long rock cutting, and see the same gneiss entangled -in a 

warped and overturned syncline and more highly metamorphosed and 

contorted.

One of the be§t places to study the series from the blue-quartz gneiss 

up to the Cheshire quartzite, and especially the relations of the conglomerate to the pre-Cambrian gneiss and the transition of the conglomerate gneiss into the sugary tourmaline-quartzite, is in the northwest 

corner of Washington, where a blind road, not on the Survey map, 

runs north from a schoolhouse to the house of H. C. Congdon.

The blue quartz is extremely abundant and ,of rich color. Allauite 

is present, and.parts of the ledges hear the barn and spring are crushed 

into a granulite, which can only be distinguished as pre-Cainbrian by its 

association with other pre-Cambrian rocks and by its position below the 

Cambrian. On the west it is covered unconformably by a fine muscovitic conglomerate-gneiss, which is more gneissoid farther up from the 

base, and where a wood road crosses the brook it becomes a tourmalinebearing quartzite, slightly muscpvitic. Next west, and thus higher up 

in the series, it is a fine, white, massive quartzite, forming the first range 

of hills and becoming schistose as one goes down into the limestone 

valley.

It is in places a very feldspathic quartzite, and by the decomposition 

of the feldspar becomes quite regularly porous, having formerly found 

some use as a buhrstone.

While through all the western halt' of the Becket quadrangle the
EMERSON] ' CAMBRIAN SYSTEM. 73

lower part of the Cambrian is everywhere more or less conglomeratic 

near the older rocks and more or less a quartzite in its upper part, in 

the broad eastern band the inetamorphisin is more severe, and this 

division can not be carried out.

Down the east border of the area across Windsor and Peru halfobliterated traces of pebbles occur here and there in the lower half, but 

the whole upper portion is mainly muscovite-gneiss. The gneisses are 

marked by a deficiency of feldspar, by the friable, granular character 

of the mass, and by the absence of all accessories except tourmaline and 

magnetite.

A mile northwest of Peru Center the true dip is marked by sandy 

layers an inch thick interposed between 2-inch schist, layers, though 

in much of the area the structure is probably secondary. Around 

Peru Center the rock is a gneiss in thin flaggy beds, with the mica 

mostly biotite. The degree of metamorphosis increases steadily southward.

Across Becket the rock is a friable, well-banded but often thickbedded biotite-gneiss, like that of the Monson quarries but even more 

massive and granitoid, and this quarry granite borders the Coles Brook 

and the Alderman pre-Cambrian limestone beds, the regular granitic 

texture seeming to depend on greater dynamic inetamorphisni accompanying the sharp upfoldiug of the limestone. Where it occurs along 

the railroad from North Becket to Coles Brook it is a good building 

stone, and in the quarries by the railroad the passage from the flaggy 

to the massive varieties can be clearly seen. Just west of the Coles 

Brook crossing the rock beside the railroad is flaggy and in flat undulations. In the quarry above, it is massive, thick-bedded, and granitoid, 

and is somewhat mixed with pegmatite in small veins.

In the south part of Becket the gneiss becomes a thick-banked, completely granitoid, light-gray gneiss, which furnishes the fine quarry stone 

of the Chester Company's quarries in the extreme southeast corner of 

the town, and the same rock extends south into'Otis. A thin section 

of the rock appeared highly crystalline, very fresh, and of completely 

gneissoid structure. The large plagioclases were full of small crystals 

of biotite and of black rods some stout and straight, some minute and 

curved. The quartz grains were full of sheets of cavities with large 

moving bubbles. The biotite was everywhere intergrowu with muscovite, though to the eye the rock seemed purely biotitic. It gave no 

indications of strain, but rather showed signs of complete recrystallizatiou.

In Monterey and in the area south of New Marlboro bordering the 

pre-Cambrian the Becket gneiss is quite normal across the whole length 

of the quadrangle to the south. It is much of the way a massive, white, 

granitoid quarry gneiss; the biotite is jet black. Very small garnets are 

numerous, and the rook is characterized by minute magnetite octal)edra. 

These seem to be dissolved through the influence of lichens, and the
74 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

rock then weathers white. After rains they accumulate by the roadside 

as iron sands.

One or two bands of a jet-black, fine-grained biotite-hornblendegneiss occur about one-fourth of a mile east of the boundary with the 

older rocks. There is rarely any trace of pebbles in the gneiss along 

the boundary or elsewhere

The amount of quarry gneiss is inexhaustible, and the rock from the 

large quarry on Ball Mountain, Norfolk, can not be distinguished from 

the Becket and Monsou quarry rock. In Otis the white gneiss branches 

.on the pre-Cambrian, and its western lobe runs down west of Filley 

Mountain to the Tyringhain fault, while its border portion continues 

down the eastern part of the quadrangle inclosing Great Pond and the 

Otis reservoir. It is a very uniform biotite-gneiss. The jet-black 

biotite is generally disseminated through the rock, at times concentrated in rounded or elongated blotches or in distinct banding. It 

generally bleaches at the surface to a dead white, but always contains 

much magnetite in minute octahedra. At. times it is strongly muscovitic, as where the East Granville road crosses the east line of .the quadrangle, and at the northeast slope of Noyes Mountain. Where it enters 

the Sandisfield quadrangle it is largely garnetiferous, but this characteristic disappears to the south. Only one small hornblendic bed 

occurs in it. This is east of D. Goddard's, a mile east of Otis Center.

Considerable excavation for iron has been made west of T. Fay's, a 

mile farther east, beginning more than fifty years ago. The gray gneiss 

is here a little more impregnated with magnetite than usual and carries 

hornblende.

In Otis the rock generally occurs in smooth, white ledges, with a 

fine-grained granitoid structure, very free from fissures, and breaking 

in large blocks, or, while breaking in equally large and firm blocks, 

showing a flat or wavy contorted banding from the arrangement of the 

biotite. It at times weathers into a ragged and deeply pitted and 

seamed rock, as in the remarkable bare ledge which starts from the 

southeast lobe of Otis reservoir and runs over the top of Noyes 

Mountain, a famous fox run. It nowhere shows any trace of conglomerate structure, and I have at times tried to refer portions of it to a 

certain wholly crushed facies of the Washington gneiss, but on comparison, especially under the microscope, it seemed plainly not to belong 

to that type. The Becket gneiss at its junction with the pre-Cambrian 

across Sandisfield and Tolland has been quite fully described in tracing 

the upper boundary of the latter (see p. 55) from the apex of this 

South Sandisfield lobe, to the north of which it is greatly corrugated, 

around to that village. Typical quartzite and a black pyritons quartzjite accompany the boundary and lie well down toward the base of the 

Cambrian, where the rock is usually gneissoid, so that in the southern 

part of this area I have not tried to carry out the distinction between 

the basal gneiss and the quartzite above, which is so well developed in
EMEfeSON.] CAMBRIAN SYSTEM. 75

the Becket region. All across Sandisfield the Becket gneiss is very 

generally a fine-grained, gray, quarry gneiss, of good quality for building purposes.

AMPHIBOLITES IN BECKET GNEISS.

On page 68 reference is made to pyroxenites and amphibolites derived 

from pre-Cainbrian limestones.

East of the Connecticut the Becket gneiss is often black, from excess 

of the shining black biotite and fine granular hornblende, assuming 

the aspect and relations of a crystalline schist, and seeming to have 

the same origin as the conglomerate-gneiss itself, into which it passes 

and of which it is, in my opinion, a mere ferruginous and calcareous 

variant.

In tracing the Becket gneiss of the western region south from Hoosac 

Mountain I did not find any hornblendic beds until the locality at 

H. Hawes's, in Middlefield (see p. 70), and the Chester Company's 

quarry in Becket were reached.

FIG. 16. Ampbibolite dike (a) in white granitoid Becket gneiss (Gb) with pegmatite contact rim (p);

quarry, Becket.

At the latter place a great mass of a fine, jet-black, massive and friable 

biotite-amphibolite extends, with a width of 12 to 15 feet, across the east 

wall of the great quarry (see fig. 16). It tapers to a point at the north 

end, and a separate or faulted portion of the main dike appears at the 

south end. It contains blocks of the white gneiss and, what is very 

peculiar, is separated from the inclosing white, massive biotite-gneiss 

by a quite continuous band of a coarse muscovite granite or pegmatite 

a foot wide, a phenomenon which is repeated several times farther 

south, as at the Ball Mountain quarry and at the West Norfolk cut.

Under the microscope the rock shows in a fresh, limpid ground of 

granular quart/ and-plagioclase-feldspar (the latter gave in plates parallel to M, the optical figure of oligoclase), and abundant grains of hornblende, biotite, and magnetite. In many of the occurrences farther 

south the grains of each mineral have nearly a common size, giving the 

slide a very regular look. Here many smaller flakes of the same minerals are inclosed in the feldspars.

Some of the black ore grains are surrounded by titanite (leucoxene). 

It is not, however, nearly so abundant as in the Middlefield bed 

described on page 70. Titanite generally characterizes the amphibolites
76 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

in the Cambrian beds, which I have considered to be derived from gabbros or diabases, and is absent in the similar beds which I have supposed to be altere'd calcareous deposits.

From this point on, going south, the hornblendic beds grow more 

abundant in the white gneiss and come to be quite characteristic of 

the basal beds of the Cambrian near the contact with the underlying 

pre-Cambrian. This is so uniformly the case in the region surrounding the Bear Mountain anticline that it gives a safe indication of the 

position of the boundary where it is concealed. The beds are generally 

without structural indications of eruptive origin, are often more biotitic 

thanhorublendic, and, as they are always interbedded with the gneisses, 

have probably had a similar sedimentary origin. They are too small to 

be represented on the map.

The hornblendic rocks are even more abundant in Norfolk, and 

both the sedimentary and the intrusive kinds are represented. Haystack Mountain, Ball Mountain, and the high hill to the east are 

largely composed of arnphibolite and seem to owe their height to its 

durability. In the quarry on the east face of Ball Mountain is a 

black dike exactly like the Becket dike previously mentioned. The 

country rock is the granitoid white Becket muscovite biotite-gneiss. 

It contains inclusions of a black rock much like the dike. The dike is 

wholly inclosed in the gneiss, is 8 feet wide, and extends 5 rods south 

before being covered. It is cut by a dike of pegmatite a foot wide a 

clear, gray rock with idiomorphic quartz, much .plagioclase, and shining, black biotite which is coarser than the biotite of the gneiss.

The rock is the same black granular rock, suggesting tine-granular 

tourmaline, but slides cut from different parts of the mass vary materially, while the hornblende and the black ore surrounded by titanite are 

the same. In one slide the biotite is of even size with the hornblende 

grains and free from inclusions, and the abundant colorless ground is 

largely granular quartz; in the other slide the large porphyritic biotite 

scales inclose all constituents except hornblende, and the ground is a 

fresh, granular, mostly untwinued feldspar, with the border of each 

grain differing sharply from the center.

The whole top and west slope of Ball Mountain are composed of the 

same black, massive, hornblende-biotite rock.

In the southeast wall of Ball Mountain the light gray gneiss wraps 

round the rectangular south end of the black, massive ainphibolite 

exactly as if that had been a more massive foreign body in the conglomerate-gneiss at the time of the folding. This is like a diabase 

dike, but it is also like a displaced limestone bed, and either one may 

be changed into an amphibolite. (See p. 64.)

Haystack Mountain, on the contrary, is made up of a highly contorted hornblendic, gneiss, generally biotitic, pyritous, or garnetiferous, 

thin foliated ami carrying intervening thin bands of a white gneiss a 

foot or so in widtu, which look like dikes in the black rock.
U. S. BE OLD GI GAL SURVEY. BULLETIN NO. 159 PL.Y.

DETAIL AT 1 ON SECTION

Scale

SILURIAN CAMBRIAN

SECTION ON I1.R.AT A-B ON MAP

EDO O

Scale

Ip^U^fXtiBMlC^, N^ V

^fe^ ,^% Ak

LEGEND

PRE-CAMBRIAN

Aw

DETAIL AT 2 O-N SECTFOIT

Scale

ERUPTIVE

Stockbrid^e limestone Becket gneiss HoTnbleiulp-schist ^VashingtDn gneiss HiiisdaLe liiaestoite Pegmatite White

NORFOLK RAILROAD CUT AND MAP SHOWING LOCATION, WITH DETAILS.

Ampliibolite

A.HoeiiA-Co.Idth.Balttj,
BMEESON.] . CAMBRIAN SYSTEM. 77

The great railroad cut west of West Norfolk Station shows all the 

relations of these rocks to the best advantage. It is illustrated by the 

section on PI. V. Entering the cut from the west the rusty preCambrian gneisses (Aw) occupy the first 28 rods. At first they are 

granitoid and carry graphite. They are succeeded by light actinolitegneisses carrying garnet. Both minerals are indicative of the near 

presence of limestone in the rock. These are all characteristic preCambrian peculiarities. Then comes a fault marked by a pegmatite 

(p) layer, and this is followed by the light biotite:gneisses ( b), which 

carry near the base a heavy baud of thin-bedded micaceous quartzite.

On passing an interruption in the cut we again come to the same 

gneisses, in which is a great dike-like mass of ainphibolite (a), or what 

may be taken to be a wholly altered basic eruptive.

This is immediately followed by another entirely similar bed, which 

includes great masses of the gneiss and has a sharp but irregular 

boundary against the inclosing hornblende-gneiss ( bh), which latter, 

from the analogy of the similar bed described below, seems to be older 

than the two dikes described above and to be of sedimentary origin. 

Then follows the foliated and finely twisted amphibolite bed (at 1 in the 

section), which is given in detail on PI. V. The contorted foliation of 

the inclosing schist runs parallel with the walls of the black bed; and 

both are partially sheared asunder and quartz veins occupy the distant 

shear planes.

Near the east end of the cut is a broad bed of a fine-grained white 

granite (g), which on the east abuts against the foliated amphibolite 

(at 2; see detail figure) and includes great angular blocks of it, together 

with the common gneiss, thus showing that both these rocks are older 

than the granite. At the east end this granite is cut by two dikes of 

the black massive amphibolite, into which it sends tongues, thus showing 

that this massive amphibolite is newer than the foliated amphibolite. 

The granite has produced a marked rnetarnorphic effect upon the black 

rock. An outer layer of the latter a half inch wide has lost its banding 

and is of much coarser grain.

In both cases a selvage of pegmatite separates the amphibolite from 

the white granite. These foliated amphibolites lack some of the peculiarities of the amphibolites derived from eruptives and resemble those 

derived from limestone described on page 69.

The two dikes just mentioned share all the properties of those 

described above from near the west end of the cut, but differ considerably in minor matters.

The dike, with inclosures, at the twenty-first telegraph pole from the 

west end of the cut is the normal type of the Cambrian eruptive amphibolites or metadiabases. It is a blackish gray, massive, fine-grained 

rock, made of shining hornblende needles, biotite .scales, and a small 

amount of white interstitial matter just visible to the eye.

Under the microscope plagioclase-appears, rarely twinned and with
78 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

small angle of extinction. Many large grains, which seem exactly 

like quartz, are biaxial and positive, and so are plagioclase. The hornblende is in jagged angular cuboidal grains, with strong absorption 

and deep colors a, bright yellow; 6, yellow to greenish yellow; c, blue 

green; 6>c>a Ex. 23° 29°. Meiiaccanite occurs and leucoxene is 

abundant.

The garnet-ainphibolite from the dike at the east end of the railroad 

cut is with the lens not distinguishable from the other metadiabases of 

the region. It is a massive, fresh-black, fine-grained rock, mostly black 

granular hornblende and white granular plagioclase.

Under the microscope it is quite peculiar. The hornblende has rather 

less absorption and is composed of large aggregations of small scales, 

sometimes polarizing together and grading into large grains which are 

centrally filled with large needles placed parallel to the cleavage.

The garnet grains are free from inclosures and are surrounded by a 

beautiful radiated aggregate of plagioclase blades which expels all the 

colored constituents and has exactly the aspect of the secondary waterdeposited albite filling cavities in the Triassic diabase from Greenfield.1 

The resemblance is so exact that one may feel sure that this limpid 

plagioclase is also water deposited. The plagioclase molds the garnet 

grains and radiates from them. The two minerals occupy angular 

spaces, as if they replaced a porphyritic mineral.

The magnetite is surrounded by a very ferruginous biotite, but never 

by titanite (leucoxene). There is a little quartz pres6nt.

CHESHIRE QUARTZITE.

The basal conglomerate of the Cambrian originally passed up into a 

sandstone which is now represented by a white quartzite, often largely 

muscovitic, always deficient in feldspar, and quite regularly characterized by small black or dark-brown tourmalines. It is at times simply 

a white friable quartz-sandstone, often dug for glass making; at times 

a thin fissile rauscovite-quartzite, which can be seen to change along 

the strike into muscovite-schists or white gneiss; and at times a tough, 

massive quartzite.

In the'high ground north of Dalton village the quartzites are present 

in great force, are at times calcareous and at times muscovitic, but 

are not developed as distinct gneisses upon the Becket quadrangle. 

They are hard, massive quartzites where crossed by the roads. At the 

southwestern corner of the high ground, as represented on the map, 

they are white, sugary, glass sands, which were entered to a depth of 

180 feet in digging for a well on Mr. Thomas Alien's farm, Grasmere, 

just south of Coltsville Station.

They are at times metamorphosed into distinct gneisses. Of such a 

character is the fine.long exposure in the railroad cutting which extends 

from the railroad crossing of the Hinsdale-Dalton road, near the Oathi Bull. Geol. Soc. Am., Vol. VIII, 1897, p. 59.
EMERSON.]^ CHESHIRE QUARTZITE. . 79

0110 cemetery, north to the line between those towns. The beds sweep

111 a broad curve, with strike northeast to northwest, and represent the 

center of the overturned syncline between the two anticlines, and thus 

the top of the series.

The rock is a muscovite-schist, at times a sericite-schist, highly contorted. It dips eastward, as forming the east flank of the Dalton anticline; and entirely similar but less altered beds occupy the other 

(western) slope, of Warner Hill, dipping westwardly on the other slope 

of the anticline. Here, in the brook bed above J. S. Barton's, the 

rocks above the conglomerates are white mica-gneisses or quartzites, 

and certain beds are a pure quartzite full of quite large drusy cavities, 

now partly filled with kaolin from the alteration of feldspar. The rock 

rarely contains small tourmalines and magnetites.

The metamorphosis of these beds plainly decreases toward the north 

and west in the region under discussion, so that the minimum of change 

appears in the northwest corner, on the brook last mentioned.

The quartzite along the west slope of the Dalton anticline is very 

thin bedded, and the greatly corrugated and discordant layer of the 

mica-schists upon it makes it probable that part of its thickness may 

be concealed by a fault.

South of the South Dalton fault, on the high ground southeast of 

Pittsfield, the quartzite widens into a broad area. It lies nearly horizontally and rises eastwardly in soft undulations. Where the Pittsfield-Washington road crosses the corner of Dalton and makes a large 

bend to the east the rock carries so much muscovite that it deserves 

the name of a schist, but it does not approach in type the higher 

schists and has all the characteristics of the quartzites (tourmaline, 

sandy structure). The same is true on the next road south, south of 

S. Hines's, where mica-schist is shown on Professor Dana's map. These 

quartzites pass around the north end of the Washington anticline in a 

broad flat syncline in the conglomerate-gneiss, which extends far out 

over the high ground in a very unusual position for such soft and 

slightly metamorphosed rocks. Just where they are cut by the line of 

latitude 42° 25' they overhang Sackett Brook in bluffs more than 100 

feet high.

They are dug as glass sands at the extreme southeast end of this 

syncliue south of Ashley Lake, in the middle of Washington. They 

are everywhere characterized by fine tourmaline needles and are generally muscovitic in greater or less degree.

KAOLIN FROM THE QUARTZITE.

Professor Dana has called attention to the decay of the quartzite 

south of Ashley Lake, in Washington, and to the formation of sand 

therefrom, and explains this decay as due to the decomposition of the 

feldspar in the feldspathic portions of the sandstone.

The quartzite, which varies from the hardest to the most friable and
80 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

from massive to thin bedded, has at times quartzose layers alternating 

with thin seams of soft kaolinized feldspar.

Many kaolin beds of western New England occur in quartzite, and are washed out 

from the decomposed quartzite. This is true of the largest of these deposits, that 

in the southwest corner of New Marlboro, near the Canaan boundary. The kaolin 

is sandy and contains quartzite fragments.

Feldspathic quartzite occurs near the line between Lenox and Washington. Lnrg'e 

cavernous blocks lie over the fields, with cavities an inch or more long.

Dr. 0. Dewey says it is wrought into millstones after the manner of 

the Paris buhrstones, and is known as the Pittsfield buhrstone. l

Feldspar still exists in some of the cavities. Prof. E. Hitchcock recognizes the feldspathic character of the rock in his Massachusetts 

Geological Eeport of 1842, saying (page 587) that the buhrstone is 

" a variety of gneiss rock whose feldspar has decomposed and disappeared, and in which quartz, was greatly the predominant ingredient." 

The name "gneiss," which has been given it, is not so far out of the 

way as might at first seem, for some of the rock contains, besides feldspar and quartz, a little mica.

The hearthstone quartzite quarried less than a half mile south of this 

locality, which affords the best hearthstones of western New England, 

contains black mica, in' very minute scales disseminated through it, 

like much of the quartzite elsewhere.

Professor Hitchcock mentions another locality, 4 or 5 miles south of 

the spot where millstones are prepared, at which the rock " may be 

seen in all stages of the process between gneiss and buhrstone." 2

QUARTZITE BRECCIA.

I have mentioned the breccia found along the South Dalton fault. 

The massive quartzite is shattered, the fragments being often moved 

on one another and cemented by limonite. It was first described by Dr. 

Chester Dewey in 1824,3 and is mentioned by President Hitchcock in 

his report of 1841 (p. 588). He enumerates it in his catalogue of the 

State collection in 1841 (Nos. 604-606) and 1856 (quartzite, Nos. 59,60, 

and 107,108) as brecciated quartz; cement hematite. It is attributed 

by Professor Dana to the wedging open of the fragments by " the 

extremely slow action of the depositing limonite." 4

I have found it so closely associated with faults that I have no doubt 

that it is a fault breccia, produced by friction along the great transverse faults, the fragments being afterwards cemented by infiltrating 

iron solutions at so low a temperature that the cemeiit is limonite.

1 Am. Jour. Sci., 1st series, Vol. VIII, p. 17.

2 J. D. Dana: Am. Jour. Sci., 3d series, Vol. XXVIII, p. 448.

* Am. Jour. Sc : ., 1st series, Vol. VIII, p. 18.

« Pseudobreccia, by J. D. Dana: Am. Jour. Sci., 2d series; Vol. XXVIII, p. 451; Vol. XX-IX, p. 57.
EMERSON.] SILURIAN SYSTEM. 81 

TRANSITION OF LIMESTONE INTO SANDSTONE.

In the single spur which projects into Lake Garfield, in Mouterey, 

from the middle of its southern shore is a ridge of the white limestone 

resting upon a highly calcareous sandstone and dipping 50° S.

At the south end of the Monterey pre-Cambrian (see p. 60), south of 

the brook opposite the E. E. Smith place, the pure white limestone 

is full of white pyroxene crystals and quartz veins and grades into a 

rusty biotite-schist. It is sandy in some places and black and flinty 

in others.

A few rods north of the village of New Marlboro, and west of the 

north road, is a white, friable, micaceous sandstone, which is pounded 

to a white sand by the feet of cattle. It is very calcareous arid lies 

almost horizontal in the Becket gneiss, into which it passes.

Along the south slope of Dry Hill, northwest of New Marlboro, 80 

rods northwest of D. S. Powell's house, is a row of outcrops, 125 rods 

long, of the Stockbridge limestone, resting as a thin layer upon the 

banded micaceous quartzite. It wraps round projections of the schist, 

dipping away from them on all sides, and passes gradually into the 

schists below.

SILURIAN SYSTEM. 

HOOSAO SCHISTS.

Windsor mica-schist bed. The anticlines of pre-Cambrian gneiss along 

the eastern side of Berkshire County are flanked east and west by lightcolored conglomerate-gneisses, and these are followed on the east side 

by a series of mica-schists, at first garnetiferous, then feldspathetic 

(porphyritic), and still higher up sericitic.

The careful studies of Professor Wolff 1 have traced these schists 

around the north end of the Hoosac anticline and down its western 

flank to where they run out onto the gneiss as a narrow band which 

finally disappears just northwest of Savoy Hollow. In this passage out 

onto the gneiss the mica-schist lies in a syncline in the gneiss running 

southwardly, and it is probable that the mica-schist described below is 

the continuation of the same bed.

The boundaries of the bed can be rudely defined by bowlders west of 

Windsor Hill, nearly 3 miles south of the above-mentioned terminus of 

the Hoosac schists in Savoy, and abundant outcrops of the rock soon 

appear and continue in a high, narrow ridge to the Hinsdale line, just 

east of the reservoir.

It can be best studied at A. W. Warren's. It seems to lie in a westwardly overturned syncline in the Cheshire quartzite, which lies in 

the newer gneiss, but with only a narrow seam of the latter separating 

it from the old pre Cambrian graphite-gneiss.

It strikes N. 10° to 20° E. and has high dips to the east, but is for the

1 Mon. TJ. S. Geol. Survey, Vol. XXIII, p. 80.

Bull. 159 6
82 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS, [BULL. J59.

most part so twisted and contorted that no prevailing directions appear. 

It is a coarse, black, garnetiferous mica-(biotite) schist, highly graphitic 

or coaly, causing the black color. The garnets are of the form 110 

and small. Quartz veins with sulphides occur.

Goltsville mica-schist bed. The whole hill east of and overlooking 

Coltsville and forming the western foothill of Davis Hill, northeast of 

Dalton, is composed of a dark lead-gray mica-schist or phyllite, greatly 

contorted and aboundiug in fine quartz veins with large quartz nodules which look like pebbles. The rock is plainly graphitic and contains a few garnets. It dips southeast beneath limestone.

Dalton bed. Following west down Barton Brook, on the west slope 

of Day Mountain, from the contact of the older gneiss and the conglomerate-gneiss at the clubhouse (see fig. 4, p. 40), one passes over the 

whole of the latter and a great thickness of the white quartzite-gneiss 

lying strati graphically above the conglomerate, all having a strike N. 

40° E. and dipping 30° W. beneath another bed of these schists. The 

nearest outcrops of the quartzite to the schist are at the road crossing 

of the next brook south, so that only a small thickness of intervening 

strata remains concealed.

The schists are here greatly contorted, strike irregularly K 70° E., 

have high dips to the west, and are plainly discordant to the gneisses 

below. 

These schists advance westwardly to the railroad, and at the foot of 

its embankment runs the Housatonic River. At the Carson & Brown 

Company's paper mill on this stream, just opposite the schist, the 

boring of an artesian well went down 135 feet through limestone containing a 20-foot bed of quartzite, and at that depth the drill dropped 

3 feet, in a water seam said to have been full of worn pebbles, onto a 

surface of the same black schists, in which the boring was continued 

9 feet. I have compared fragments of the schist from this boring with 

the adjacent ledges and they are identical. This brings these schists 

into the same position as the schists previously mentioned at Savoy 

and Windsor. On the other hand, these Dalton schists differ from the 

schists which succeed the white gneisses on the east'in Middlefield and 

Becket.

Mica-schist of Dry Sill in New Marlboro. The mica-schist which 

wraps around the quartzite of Dry Hill in New Marlboro and grades 

into the Stockbridge limestone occupies precisely the same stnitigraphical position as the Dalton schist. It is composed of thin bands of a 

white, sugary quartzite, one-fourth of an inch to 1 inch wide, with 

equally thick intervening layers which are quite micaceous. The mica 

is fine grained and generally muscovite, though sometimes much biotite 

is present. High up the hillside the rock is a dark mica-schist, its 

dark color due to excess of biotite and hornblende.

Eastern band. At the base of this formation a dark, highly gariietiferous mica-schist forms the passage bed from the Becket gneiss to the 

main portion of the series.
EMERSON.] HOOSAC SCHISTS. . . . 83

The latter has the habit of a mica-schist, although it is generally 

quite feldspathic. Small rounded crystals of albite, scattered porphyritically in the mass, have in crystallizing often cemented several grains 

of quartz together.

Both micas are present and the rock is generally quite dark, from the 

abundant biotite. It shares with the following formation the greasy 

feel from the hydration of its muscovite.

The base of the bed is exposed on the road lying east of Peru Center, 

at D. E. Ingalls's, the second house to the south after leaving the village. 

It is here a coarse and corrugated feldspathic mica-schist, full of garnets 

as large as raisins.

Two miles northwest of Peru Hill, at the stone schoolhouse, the upper 

boundary of the Hoosac schist upon the Rowe schist is exposed for a 

long distance on the bare hill 50 rods east of the schoolhouse. The rock 

is a gray porphyritic gneiss a rock with the habit of a coarse sericiteschist but abundantly porphyritic and with small oval spots of white 

feldspar. It is well exposed east of Bancroft station on the Boston and 

Albany Road, beginning with the mouth of Factory Brook and extending 

a half mile east. At the base it is a coarse sericite-schist, full of garnets 

one-third of aiiinchacross, and thesamebed extends north to Middlefield 

Center and beyond. In the upper part the garnets are absent, and 

sandy layers alternate with the more micaceous bands. This continues 

to the bridge east of the station.

The next accessible section of the series is along the road west from 

Chester station, just within the limits of Becket. Where, at the southeast corner of the Becket quadrangle, the road goes south from Walker 

Brook to the Chester Company's quarry the brook cuts a contorted, 

light-gray, thin-bedded biotite-gneiss, with layers two-thirds of an inch 

.thick, strike N. 15° W., dip 70° E. It has muscovite on foliation faces 

and much of it is soaked with pegmatite.

A little east, halfway to the next house, a highly inuscovitic saccharoidal gueissis kneaded in with a highly garnetiferous, rusty mica-schist, 

of quite coarse grain, which forms the basal layer of the terrane under 

discussion. Strong, coarse mica-schists follow, mainly coarse films of 

muscovite scales and an arenaceous quartz ground with no bauds or 

nodules of infiltrated quartz, few garnets, and rarely blotches with feldspar aggregates. A thin section of the rock from the east of Becket 

(E. B. Bichards's) shows a gray, rusty, muscovitic gneiss; raveled and 

ragged intergrowths of muscovite and biotite and a mosaic of quartz 

grains wrap round porphyritic " augen " of albite, which in places shows 

extinction according to two laws and the granophyric structure in every 

variety and of great beauty. The garnets are centrally filled with 

brightly polarizing black rods and long blades of biotite.
84 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

ROWE SCHIST.

Only a narrow band of the Kowe schist runs down the eastern border 

of the sheet for half its length. The small porphyritic albites disappear 

and the rock becomes a softer sericite-schist blotched with green, due 

to chlorite spots derived from altered garnets. Going east from Bancroft station to the third bridge one finds the boundary and a sudden 

transition from the albitic schist below. Along the railroad two bands 

of amphibolite occur in this formation before the edge of the quadrangle is reached. Along the east line of Becket, east of the Chester 

Company's quarries, it contains a gray cyanite, which includes small 

garnets with the centers filled with black grains. The cyanite is often 

changing into muscovite. (See PI. I, fig. 6.)

Where the schist enters the Sandisfield quadrangle it is a hard, 

ragged, contorted muscovite-biotite-schist barren of accessories, slightly 

rusty and quartz veined; the zigzagged bedding goes N. 40° W., the 

cleavage N. 50° W. Higher up it has small hornblende-schist layers 

and is in places garnetiferous and of greasy feel.

STOCKBKIDGE LIMESTONE.

Only a narrow portion of the white crystalline limestone which underlies and has conditioned the broad Housatonic Valley, enters the area 

on its western borders and extends far east into broad depressions in 

the older rocks in Dalton and Tyringham and into smaller recesses south 

of the fault on the south line of Daltoii and at East Lee. Its boundary 

is thus for 10 miles a straight line parallel with and near the western 

edge of the Becket quadrangle, while the broad sands of the Housatonic 

conceal nearly every portion of the limestone in the low valley bottom.

The scarp of the older rocks, which looks down on the limestone valley, is offset to the west in Bear Mountain, and on the southern half of 

the area the eastern boundary of the valley limestone lies far west of 

the territory covered by the map. The rock also extends eastward in 

a great lobe far out over the highlands in Mouterey, and two smaller 

lobes enter the area at New Marlboro and at West Norfolk. In its northern portion it is mainly a calcareous carbonate and is for the most 

part free from accessory minerals. I have collected rutile and brown 

tourmaline in the quarry at Coltsville. It is a white-to-gray marble, 

every where quarried locally and furnishing good building stone in inexhaustible quantity, so that the location of quarries is mainly dependent 

upon the proximity to railroads. Much has been written about a flexible 

variety of the marble (see Calcite in lexicon, p. 107) occurring near 

Pittsfield.

Farther south the extensive quarries at Lee are within the limits of 

the area considered, and from these quarries much marble has been 

shipped to Washington, Philadelphia, New York, and Albany. Here 

some beds of the rock are filled with a white-bladed tremolite, which is 

represented in every mineral cabinet.

This limestone is thickly covered in the bottom of the Tyringham
HYDES FALLS.
EMEBSON.] STOCKBRIDGE LIMESTONE. ,85

Valley. For a long distance north of the fault it is absent, and in 

this distance the springs and wells on the north of the fault give soft 

water and those on the south of the fault give hard water. At Mr. D. 

dark's and eastward the limestone is preserved on both sides of the 

fault, but is very thin. All the springs are of soft water.

The limestone that runs horizontally high up on the south side of 

the Tyringham Valley at Fernside is the common, gray, barren Stockbridge marble. On the hillside across the strike the pure limestones 

grade into gneiss, through a large series of calcareous schists, often 

very rusty. The series is thus inverted and is the upper limb of a 

small fold overturned to the north, its axial plane dipping south into 

the mountain.

On the other side of Bear Mountain the limestones dip northeast 

into the mountain; they can not go under it, as its nucleus is preCambrian. There is thus some form of fan structure present here, 

as was suggested to me by Prof. T. Nelson Dale. (See section on the 

Bear anticline, p. 58.)

The Monterey limestone grades in every direction into a sugary calcareous quartzite, and this, w'ith the exceptionally heavy cover of till, 

makes it impossible to put accurate boundaries on the map. At the 

branch in the road south of the outlet of Lake Garfield is a broad 

area of a white, sugary limestone with much white pyroxene overlain 

by a rusty jointed, black, pyritous quartzite. The accompanying plate 

(PI. VI) shows a beautiful anticline in this limestone at Hydes Falls, 

1£ miles south of Monterey.

Farther south other remnants of the marble exist on the surface 

northwest of New Marlboro, and several instances of its passage into 

the Cambrian gneisses and quartzites are given.

Of 25 analyses of the Stockbridge limestones given by President 

Hitchcock,1 12 show it to be pure calcium carbonate. The remaining 

samples are strongly magnesian but quite free from silicious impurity, 

while in 5 analyses of pre-Cambrian carbonates the rocks are nearly 

pure dolomites with an average of 11 per cent of silicious impurities.

GEOLOGY OF FERNCLIFF RIDGE IN LEE. 

CAMBRIAN QUARTZITE.

The geology of the prominent ridges which rise within and just east 

of the village of Lee (see map, PI. VII) is complicated by the unexpected appearance of an outlier of the Cambrian tourmaline-bearing 

quartzite in the midst of the normal Silurian series.

This quartzite forms a peculiar ridge, which starts with Ferncliff, in 

the middle of Lee, and is a picturesque steep-sided mass of native rock, 

in whose eastern side an interesting cave has been formed by the falling of the jointed quartzite from the vertical face of the cliff.

1 E. Hitchcock: Geol. Report of Mass., 1841, passim.
86 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

The ridge has been cut through by the river, but rises immediately 

on the north side and runs a mile farther northwest, presenting vertical cliffs to the east and lower bluffs to the west, where its shape is 

masked by a thick coating of drift. It ends abruptly at the south end 

of Laurel Lake, its northern and western faces showing 100 feet or 

more of vertical or overhanging cliff.

Litliology. In Ferncliff the Cambrian series is represented by a thinbedded micaceous quartzite, quite gneissoid in its granular texture and 

its irregularly disseminated biotite scales, and although it is slightly 

feldspathic it is not sufficiently so to be called a gneiss. It is uniformly 

fine sandy granular, and abounds in minute well-formed brown tourmalines in six-sided prisms. It is full of small lenses and pockets of 

quartz, and the tourmaline, in irregular aggregates, is much concentrated in and around these small veins and in their prolongations, being 

here much larger, some prisms reaching fully an inch in length.

This bed, 40 or 50 feet thick, makes the crest of the ridge, and beneath 

it is a more micaceous quartzite or arenaceous mica-schist, always having a sandy quartz base, but often dark gray in color, owing to the 

abundance of biotite mixed with the m'uscovite. This also regularly 

contains tourmaline, in shapeless groups of needles, clear down to the 

edge of the river at the north foot of the hill. The same conditions exist 

in the ridge to the northwest. The rock is tourmaline-bearing from top 

to bottom, except in the middle of the e.ast face of the steep hill which 

forms its north end, where there is, in considerable force, a pure white 

quartzite containing only a few minute pyrite cubes. It is, however, 

more granular than the Silurian quartzite to the east and more regularly 

banded, and layers immediately above and continuous with it contain 

much mica and tourmaline.

Structure. In Ferncliff the rock is much contorted in the west face 

of the ridge; its beds dip east into the hill, with high angle, and emerge 

in the same direction, with low dip to the east as a whole but with large 

low undulations of the beds to north and south and with low dips to the 

west in some places, as at the cave.

On the north face of the Ferncliff hill the beds dip first 20° E., then 

30° E., where they are on a level with the Silurian quartzite to the 

west; 60 feet lower, at the river bank, they are nearly horizontal, with 

low dip south. At the north end, in the same way, the dip is 70° to 80° 

E. all the way up the west face, with low easterly dips on the east side. 

In the high ground of the valley border, several miles to the east, the 

equivalent of these rocks appears as the Cheshire quartzile, which 

graduates into the Becket gneiss, and they are here, for a long distance 

north and south, characterized by an abundance of minute stout tourmaline prisms. They are much more highly metamorphosed than the 

Silurian rocKs with which they are here associated.
U. S. BE OLD GI GAL SURVEY. BULLETIN" NO. 159 PL.VII

A. Hoen A- Co. Ltfli. Baltiin oreGEOLOGICAL MAT- OP FERNCLIFF AND EAST LEE

Scale of mile.s i____________'/i._____ o _____ i

1898
UMER8ON.] GEOLOGY OF FERNCLIFF RIDGE. 87

SILURIAN SEEIES. 

LOWER LIMESTONE.

The lower band of the Stockbridge limestone which appears in this 

area is deeply buried in the low ^alley bottom and rarely exposed at 

all. At the railroad crossing in the north edge of Lee village, opposite 

the Columbia mills, where on the map the eastern quartzite band 

crosses the road and railroad, is a section which shows all the remaining rocks of the area in excellent exposure, all dipping eastward in 

apparent conformity, and just south, along the railroad, the lower limestone is also well exposed in the cutting. It is full of phlogopite in 

bands, especially at the top, of altered pyrite in pentagonal dodecahedrons, of granular colorless muscovite, and of quartz grains. Its calcite 

grains are much twinned.

It folds around a large lens of a very coarsely crystalline and limpid 

marble, and is as a whole so much more crystalline, translucent, and 

filled with minerals than the soft, fine, sugary limestone of the upper 

bed as to strongly suggest that it may belong to the pre-Cambrian 

limestone, like that of the East Lee Valley. I could not find chondrodite 

or pyroxene in it, and consider it a Stockbridge limestone rendered 

more highly crystalline than usual, perhaps by the influence of faulting.

The accompanying analysis of a specimen of this limestone, from the 

railroad cut in Lee, also goes far to prove that the rock is to be associated with the Stockbridge limestone. The analysis was made by Mr. 

George Steiger in the laboratory of the United States Geological 

Survey.

Analysis of limestone from cut west side of railroad, north of Lee village.

SiQt....... .........................................................

Ti02 . ............................... ...............................

Al^Os. .............................................................

Ft^Os..................................... .........................

FeO ..............................................................

CaO ...............................................................

BaO.................................................... ...........

MgO.. .............................................................

K20 ...............................................................

T3*tO..... .........................................................

Si2 0 ...............................................................

WaterlOO0 ......................................................

Water 100°+ .......................................................

so3 .... ................ ............................................

 p f\

C02 . ...............................................................

Total........................................................

Per cent.

0.95

.09

.10

54.75

.56

.15

09

.08

.05

ni

43. 38

100. 16
88 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

I have elsewhere brought together (see p. 69) four analyses of the preCambrian limestones of western Massachusetts. They are all nearly pure 

dolomites and contain an average of 11 per cent of siliceous impurities.

In a list of 25 analyses of the Stockbridge limestones 12 are nearly 

pure calcium carbo'nate, and those which contain magnesia are nearly 

always free from siliceous impurity.

BERKSHIRE SCHIST.

This mica-schist, which is well exposed just east of the railroad crossing on the foregoing section and in many places to thelsouth as well as 

along the southwest shore of Laurel Lake, is a felted mass of warped 

red-brown biotite scales, generally of quite ragged appearance, rusting 

readily, and without accessories.

SILURIAN QUARTZITE.

The quartzite which appears near the schoolhouse just west of Ferncliff, and which has been recently opened for road material across 

the river to the northwest, agrees exactly in composition with that of 

the ridge a mile east of Ferncliff. It is the usual pure, massive, paleyellow, vitreous quartzite.

It diminishes rapidly in thickness toward the west and north. At 

the south end of the east baud it composes the whole of the massive 

hill just east of Lee (1,131 feet high), while where it crosses the railroad 

it is less than 50 feet thick. Farther north the rocks are everywhere 

covered, but all the indications of topography point to its entire disappearance, as at the north end the mica-schist ridge slopes down gradually into the low limestone plain, whereas a strong ridge would rise 

to the east if the quartzite were present. The quartzite west of 

Ferucliff is also only about 50 feet thick, and seems to thin out to the 

northwest so that it ceases to have influence upon the topography.

UPPER LIMESTONE.

This is the common Stockbridge limestone, white or pale gray, friable, 

generally pure in this vicinity, except that tremolite is abundant in the 

quarries to the south of the town.

FAULTS.

The representation of a north-south Ferncliff fault is justified by the 

close approximation of the Silurian quartzite to the Cambrian quartzite 

in Ferncliff, followed by the similar approximation of the Silurian inicaschist at the north end. It is drawn parallel and symmetrical with the 

main Lenox fault, which runs at the foot of the mountain to the east, 

as an overthrust subordinate to the main one, and most simply explains 

the structure of the region.

Justification for the hypothesis of an east-west fault is found in the 

fact that on reaching this line the two strong quartzite ridges suddenly 

stop and the whole area before them lies at the low level of the limestones, 

so deep indeed that over a square mile there are no outcrops at all. It 

is thus much more probable that these, resistant beds are faulted down
EMERSON.] FAULTS. 89

than that they form the surface across to the edge of the mountains, 

where they appear again in undiminished thickness.

This fault, prolonged easterly, runs up the East Lee Valley, where it 

or another fault south of and parallel to it, which is given with query 

on the map, terminates the Lenox fault and is marked by the overthrust of the pre-Oambrian on the Cambrian. It also runs parallel to 

the great Tyringham Valley fault to the south.

SIGNIFICATION OF THE NORTHWESTERN THINNING OF THE SILURIAN QUARTZITE.

I have elsewhere shown that the Tyringham and East Lee valleys 

were early blocked out because of the solubility of the Hinsdale 

limestone, and this thinning out of the coarse sediments, represented 

by the two quartzite bands (see Ssq, PI. VII), along lines radiating 

from the mouth of the East Lee Valley, may mark a time of exceptional 

elevation of the Berkshire Valley border and of strong drainage 

through the long East Lee-Otis depression. In other words, the 

quartzite and associated band of Berkshire schist represent the 

remains of the delta deposit of a stream flowing west down the East 

Lee-Otis Valley during Lower Silurian time.

FAULTS. 

HINSDALE FAULT.

/

This fault runs north and south through the village of Hinsdale. 

Along the whole western border of the Hinsdale anticline north of the 

Plunkett reservoir the Washington graphitic gneiss is absent and 

the Lee gneiss comes successively into contact with the Cambrian 

Becket gneiss, the Washington gneiss of the Dalton anticline, and the 

Stockbridge limestone.

A mile south of Hinsdale, at the top of the hill just west of the 

large outcrop of limestone near the bridge over the railroad, and again 

90 rods west of the last inhabited house (C. D. Barrett's) on the blind 

road running north from the cemetery, the Lee gneiss can be seen in 

immediate proximity to the Becket gneiss. The fine-grained micaceous 

quartzite (Cambrian) has a strike N. 10° W. and a dip 65° W. The 

amphibolite and banded gneisses (Lee gneiss) adjacent on the east 

have a strike N. 50° W. and a dip 80° W.

Farther north, at J. Hanrahan's, south of the road running east from 

Dalton, the Lee gneiss carrying allanite is for a long distance in immediate proximity to the great outcrops of Stockbridge limestone, showing that the fault is one of great importance and concealing the whole 

Cambrian and Upper pre-Cambrian beds.

DALTON FAULT.

From the high iron bridge near the Dalton railway station the 

crumbling white Stockbridge limestone can be seen to form the north 

bank of the Housatonic for a long way west, while the fluted surface of 

the massive Cheshire quartzite forms the steep south bank.

At the ruined pier of a proposed bridge this fluted surface dips 80°
90 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BOLL. 159.

]$". in the upper portion of the bluff, 50° and 40° in the lower part, and 

represents the fault surface, being horizontally ground and slickensided 

by the horizontal thrust of the fault. The limestone appears in the 

northern bank of the narrow stream to the next iron bridge, where it 

includes quartzite beds and forms the bed of the stream, with a constant 

strike N. 20° E. and a low westerly dip of 20°, as at the Carson and Brown 

paper mill, just west. .Here the adjoining rock on the south of the 

fault is a dark, corrugated mica-schist, abundant in the hills to the 

south, and in boring an artesian well at this mill and 2 or 3 rods north 

of the stream the auger went through the limestone for 135 feet and 

then dropped 3 feet onto the surface of the mica-schist, which was 

bored 9 feet. I found chips from this boring identical with the schist 

in the hill to the south. This gives the fault here a hade to the north 

about the same as the quartzite plane mentioned above. The well 

record is interesting and is given below.

The faults on the north and south of the Dalton anticline were formed 

by the crushing together and the uplifting of this anticline, and an 

inspection of the map will suggest that the two areas of mica-schist 

north and south of the fault may once have been continuous, and the 

part to the north have been pushed eastward by the throw of the fault.

It may have been a muddy band sent out over the bottom of water 

where for the most part limestone was forming, and have been continuous 

eastwardly with the remnant in Windsor and the Hoosac schists farther 

east.

ARTESIAN WELLS UPON THE DALTON FAULT.

The great paper-making mills at Dalton owe much of their high reputation to the abundant artesian water, of excellent quality, obtained 

from very shallow wells bored upon the Daltou fault. (See PI. VIII.)

At the Carson and Brown mill, beside the Housatouic Eiver, in the 

west part of Dalton village, two interesting artesian wells have been 

bored. One was commenced March 7,1884, by D. Dull, of New York. 

The following.record was given me by Mr. Brown:

EecorA of well borings at the Carson and Brown mill in Dalton in 1884.

	Feet. 

Soft rock ........................................................ 25

Hard rock ....................................................... 84

All way hard rock ............................................... 98

Little water ran over ............................................ 99 . Soft rock ........................................................ 101

Soft rock ........................................................ 102

Very soft rock ................................................... 104

Very soft rock ................................................... 109

Very soft rock .................................................... 114£

Very soft rock .......................................... J......... 117

Very soft rock; first water run................................... 1.22

Very soft rock; increased water run.............................. 126

Very hard rock .................................................. 131£

Broke through to soft rock and gravel 3 feet deep; water doubled. 135

Solid rock again .... ...................... ................. ....... 138

Continued 9 feet in the same solid rock........................... 147
BULLETIN" NO. 159 PL.YIII.

IANT WELLS ON DALTON FAULT 

Scale

A.Hoen A. Co. Rfll.Baltijnore.
EMERSON.] DALTON FAULT. 91

The well supplied 740 gallons a minute of the purest water. The 

upper rock was limestone. The drill fell in a cavity formed by solution of the base of the limestone by water circulating along the plane 

of the fault. The lower rock was the corrugated mica-schist, as shown 

by samples preserved.

In 1855 a well was bored on the west side of the mill near the river by 

S. S. Gilman, of Springfield. The following record was preserved:

Record of loell boring at the Carson and Brown mill in Dalton in 1855.

Feet. 

Rock blue lime ................................................ 24

Rock blue lime ................................................ 24-37

Gray band; first water......................................... 37-40

Gray lime.... .................................................. 40-67

White belt; large water vein, flowing well..................... 67-71

Increase of water .............................................. 71-100

"The rock is soft lime mixed with soapstone." The soapstone was 

probably the decomposed micaceous portion of the limestone. 

An analysis of the water gave the following results:

Analysis of water from artesian ivellin Dalton. 

[Parts in 1,000,000=140.3 solid.]

;

Si02 ...............................................................

A12 0S . ......... ....................................................

CaO.. ..............................................................

MgO. ..............................................................

K20+NaaO ........................................................

FeO................................................................

Cl.. ................................................................

CO..................................................................

CaC03 ...........................................................:.

MgCOs--.. ............ .............................................

Nad ..............................................................

Si02 ... .............................................................

AljOg.. .......................... ................;.................

K2 0........................................... ....................

Parts.

8.80

12.80

33.15

23.06

22.54

3.55

36.40

59.15

35.06

5.85

8.80

12.80

18.64

The wells in the village of Dalton to the north and east lost their 

water when the first well was opened. Other wells have been bored 

along the same fault, at Mr. Byron Westoii's mills farther east, but the 

wells bored at the Craue mills to the west were unsuccessful and were 

plainly not along the line of the fault. The following report on the 

wells at the Weston mills, 250 rods east along the same fault, has been 

prepared for me by Mr. W. L. Tower, civil engineer in Dalton:

Number of wells, 5, of which 4 are in use:

No. 1, the Bonanza, is 239 feet deep aud was bored in winter of 1883-84. First 

flow of water tested January 24, 1884, showed 366 gallons per minute. After further 

boring more water was obtained, aud the flow has perceptibly increased siuce the 

well was completed. The latest test shows a flow of 550 gallons per minute with a
92 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

pump lifting the water 18 feet out of well. The boring drills and part of the apparatus were lost in this well, and it is thought that this fact diminishes the flow of 

water. 1 The rock is reported to have been principally very soft limestone. Operations in boring this well were very much delayed and hindered by caving. < It was 

bored by Daniel Dull, of New York City, who saved samples of the rock passed 

through in boring the Bonanza and Deep wells.

No. 2, Deep well; 511 feet deep; bored in fall of 1883. Flow, 260 gallons per minute. Bored by Daniel Dull. Rock passed through medium to hard limestone and 

a vein of very flinty rock at a depth of about 300 feet.

No. 3, Chamberlin well; 150 feet deep; bored 1856-57. Flow, 120 gallons per 

minute. Bored by Mr. Gilman.

No. 4, Defiance well; 76 feet deep. Flow, 28 gallons»per minute. This well is 

about 400 feet northeast of the Bonanza well. Surface rock in the immediate 

vicinity, as uncovered in summer of 1895, soft seamy limestone. Bored by Jesse 

Button, Springfield, Massachusetts. An analysis, made at Yale College, of the water 

of the Bonanza, Deep, and Chamberlin wells, determined that it is very hard, contains carbonates, is unfit for use in boilers or laundry.

There is a fifth well at Weston's mills, near the Deep well bored by Jesse Button, 

but it is now abandoned. The well has a temperature of 48° for summer and winter.

-SOUTH DALTON OR WARNER MOUNTAIN FAULT.

The west end of this fault can be well studied a hundred rods north 

of where the road from Pittsfield to Washington Station first crosses 

Sackett Brook, in a narrow gorge running east and west and forming 

the gathering ground of a small brook, shown on the map, that runs 

west, crosses the north and south road, and joins Sackett Brook.

The north wall of this narrow valley is composed of the dark Becket 

gneiss, the south wall of the pure Cheshire quartzite, and they both 

strike north and south and dip west.

Going west to the next point where Sackett Brook crosses the road, 

one may take a wood road north from the western house (J. Sweeney's) 

of the small settlement 100 rods up the mountain side and 100 feet above 

the main road to a group of logging huts near a bridge.

Five rods up the brook, above this bridge, one finds the white quartzite on the south abutting against the dark Becket tourmaline-bearing 

gneiss in a well-marked vertical east-west fault, which can be traced in 

the bluff a long way east to a point where, north of the eastern house 

of the village (W. Kirschner's), the quartzite begins to come in contact 

with the older gneiss, and where the junction of the two gneisses is 

also well exposed a long distance in a steep bluff.

The fault limits the Dalton normal anticline on the south. South of 

the fault the quartzite extends a mile farther east than on its northern 

side. All along the roadside, south of the great southwardrfacing scarp 

caused by this fault, are numerous great bowlders of a coarse quartzite 

breccia cemented by much limonite a friction breccia derived from 

this great fault. (See p. 80.)

At a point a half mile north of the top of Warner Mountain the

> This was probably because the fault plane was struck at this point and the toola fell into the 

cavity, as in the case of the Brown Brothers' well, before mentioned.
EMERSON.] LENOX FAULT. 93

corner of the pre-Cainbrian area can be clearly mapped in the bare 

hilltop. From this point east the* country is covered, but the formations that come up to it on the north and on the south are so diverse 

that the prolongation of the fault is certain, and its exact position can 

not be anywhere far from the line given on the map. It is, however, 

not certain that it cuts off the pre-Carnbrian limestone at the overhead 

bridge south of Hinsdale village, although this is by far the most 

probable representation of this badly covered area!

LENOX FAULT.

A half mile south from New Lenox Boajing Brook comes down from 

the mountain. Following it up 100 rods from the road over the distinctly bedded quartzite, which strikes 45° E. and dips 50° W., increasing near the contact to 60° W., the contact above can be seen in the 

side of the wood road which follows the brook on the north side, and 

below in the bank at a fine waterfall. The quartzite is here thick 

bedded and much contorted, especially a little farther south, and its 

posture is constant. It is vertically jointed for several feet west from 

the contact and a few scales of muscovite appear on the foliation faces.

The gneiss rises in a great bluff above the quartzite, and this bluff 

extends a hundred rods north and several miles south to the East 

Lee Valley. The gneiss is highly stretched, with strong pitch south. 

It is much crushed and agrees in type with the Tyringham rock. Many 

bowlders of the coarse Washington blue-quartz gneiss, blotched with 

great masses of biotite, have fallen down, and the contact of the two 

formations is in the bluff above.

A still more interesting exposure of the same contact is found a mile 

east of Lenox Furnace (fig. 8, p. 44). A wood road runs east from a 

sharp bend in the main road, and the section shown in the figure begins 

where this road crosses a brook and continues along its side.

The contorted quartzite at the brook crossing seems to have a rather 

low dip west, but the finer, flaggy quartzites higher up dip steeply to 

the west, which seems to be the posture in the beds; flattened pebbles 

are found higher up. These beds and the thick, granitoid quartzite 

which follows (and which, as in the Dalton clubhouse section, is characterized by a pale-green muscovite) are full of small tourmalines and 

connect with the Cambrian.

At the contact, which occurs in a great white ledge south of the 

brook just before reaching the thick woods, only a rod of a true Becket 

gneiss intervenes between the micaceous quartzite and the black-andwhite pre-Cambriau gneiss. There is a conformity of foliation at the 

junction, but while the quaxtzites strike north the older gneisses strike 

nearly east, and the extent and character of the fault can not be determined. It depends upon the thickness of the gneissoid lower member 

of the Cambrian, and this is variable; at times the Cambrian seems to 

be a quartzite to its base.
94 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 150.

Five rods east of the contact of the section shown in fig. 9 on page 45, 

at the point where the road from Lenox Furnace if prolonged east would 

cut the 1,400 contour line, is the contact of the white-and-black banded 

Lee gneiss and a stretched gray Tyringham gneiss. The wood road 

runs over bare rock at this point, and there is, resting unconformably 

upon the vertical edges of the Lee gneiss, a thin veneering of a dark 

jointed Cambrian slate containing small pebbles.

The complex series of faults near East Lee can be only partially 

deciphered, and their connection with the Lee faults is not clear. The 

matter is discussed under the sections describing the East Lee limestone 

(p. 50) and the Ferncliff faults (p. 88).

TYRINGHAM FAULT.

The Tyringham fault has had much to do with the formation of the 

deep Tyringham Valley. How much it has been assisted by the solution of the pre-Cambrian limestones can not be determined.'

It brings the pre-Cambrian up against the Cambrian in the mouth of 

the valley, probably hades north, and is upthrowu on the north side. 

Lower down the valley it has brought Cambrian and pre-Cambrian 

together, and in its continuation has formed the upper valley of Clam 

Eiver, as the Otis fault has fixed the upper course of the Faruiington 

Eiver.

INTRUSIVE ROCKS.

Intrusive rocks, both basic and acid, are almost absent from the 

Becket and Sandisfield quadrangles, except so far as the pre-Carnbrian 

rocks are altered eruptives. West of the great granite stocks which 

look down on the Connecticut Valley and their broad fringe of dikes, 

the isolated dike of porphyritic granitite in Middlefield is almost the 

only acid intrusive which approaches this territory. The greatly 

altered black massive hornblendic rocks of Becket and of Ball Mountain and vicinity, associated with the Cambrian gneisses in the extreme 

southwest corner of the area, are the only exception among the basic 

rocks. The same is true of the extension of this area to the north 

across the State. Two small, much altered dikes' of basic rock are 

indicated by Professor Wqlff in the Hoosac Mountain map as northeast 

and southeast of the village of Berkshire, and a third pre-Cambrian 

dike is described from Oak Hill, on the north border of the area. The 

same seems also true of Greylock Mountain and of the Taconic Eange 

for a considerable distance to the west. The basic rocks of the Cambrian are described on page 69, in order to compare them with the 

amphibolites formed from sedimentary beds. °

Pegmatite. A well-characterized graphic granite is represented in 

Mr. D. Clark's collection, which was obtained from the roadside in 

West Otis village. The granite 50 rods below Windsor Falls, iu Dalton, south of the brook, contains good crystals of orthoclase and a little 

actinolite in biotite, and is soaked full of a lemon yellow iron salt due to
EMERSON.] INTRUSIVE ROCKS. 95

change of biotite and actinolite. In the southwest part of the Sandisfleld quadrangle small pegmatite veins and impregnations are quite 

frequent, but not extensive enough for mapping. They present no 

peculiar characteristics except at the occurrence north of Town Hill, in 

Sandisfield, where the crushing has sheared the large tourmalines in a 

remarkable way into a series of echeloned plates. The small pegmatite 

dikes bordering the amphibolite at the Becket quarry are described on 

page 75, and those at the West Norfolk cut on page 77.

GLACIAL DEPOSITS.

The whole upland country is covered by drift, often very heavily, 

especially in the south of Becket and the north of Otis, but presents 

little of special interest.

POST-GLACIAL DEPOSITS.

The Hoosac limestone valley is continued south over a low pass in 

Lanesboro into the broader Housatouic Valley at Pittsfield by way of 

Unkamet Brook. The Hoosac Mountain Range from the north line of 

the State to the north of Dalton presents so steep and uniform a slope 

to the west that it forms an unbroken line of division between the 

Champlain deposits on both sides of the range. When, however, the 

limestone expands eastward in the center of Dalton a partial union 

occurs.

This Dalton bay is deep, being underlain by the Stockbridge marble, 

which is easily removed by erosion. It is, moreover, continued southeast across Hinsdale and Washington by a curious transverse depression in the Berkshire Hills, which, although at a much higher level 

than the Pittsfleld Plain, is yet much below the crest of the ridge. Itbegins narrow, at its southeast corner, and extends as a broad depression across0 Hinsdale, where it drains west as the Housatonic, and is 

continued beyond the Washington station, where it expands into a deep 

amphitheater and suddenly narrows into a canyon, which continues into 

Becket and contains the head waters of the Westfield Eiver a tributary of the Connecticut.

When the boundaries of the complex overthrown Hinsdale anticline 

were made out, the lowest easily decomposing beds of the pre-Cambrian 

nucleus of this anticline were seen to have conditioned this depression, 

which is divided at the Washington station by a daui of the decomposing gneisses about 1,550 feet above the sea. These furnished the 

barrier which fixed the level of the Hinsdale lake in Glacial time, and 

which forms the watershed of the present topography.

WASHINGTON BASIN.

As the ice melted up the Westfield River Valley it at last set 

free the canyon already mentioned, between Becket and Washington 

stations, and the deep amphitheater into which the canyon expands
96 GEOLOGY OF EASTERN BERKSHIEE COUNTY, MASS. [BULL. 159.

just before reaching the latter station. As the waters escaped from 

the ice and passed through the gorge, they left a great body of sand in 

the basin, and this at a time which slightly antedated the formation of 

the Hinsdale lake described below.

For nearly a square mile north of Washington Station the broad, 

flat-topped sands stand 80 feet above the bottom of the Hinsdale lake. 

Eecent extensive excavations by the railroad along this plain showed 

that for long distances ii is composed of broad, undulating sheets of 

nearly horizontal sands and gravels, bending down on the south, with 

delta front structure. They were probably laid down when the ice 

still occupied most of the Hinsdale Basin to the north and had just 

begun to send its waters down the newly opened gorge to the south.

HINSDALE LAKE.

A description of the heavy gravel and fine sand deposits which fill 

the basin back (north) of the Washington sand plain across Hinsdale 

and which end abruptly in a terrace scarp on the east edge of Dalton, 

high above the level of the sands in the Pittsfield-Dalton Valley, will 

be best appreciated if given in the terms of the theory which seems to 

explain them.

The sands seem to have been deposited while the ice, having just 

abandoned the Hoosac Eange to the east, still filled the limestone valley 

to a point south of Pittsfield and projected into the Dalton bay, completing the boundary of the lake near the present western boundary of 

Hinsdale Township, and about a mile north of Hinsdale village.

The Washington gneiss barrier determined the height of the waters, 

and heavy floods from the north and northwest swept across the ice 

and into the lake, carrying great masses of sand and gravel which, 

exactly as in the filling of a mill pond, were deposited in the upper 

part of this lake, filling the narrow northern portion from the point 

where the ice stood, across the area where is now the Catholic cemetery, 

extending southward, and expanding with the widening of the basin to 

a broadly curved line just south of Hinsdale village.

The great plains to the north and east of the village (the level of 

Maple street), about 1,520 feet above the sea, are a remnant of this 

extensive deposit, and the magnificent terrace scarp which starts from 

the road running southeast from the town library and about 50 rods 

from that building and runs a half mile east to the next road, is the 

terrace front of the great delta that was advancing into the lake when 

a period was put to the lake itself.

On the recession of the ice northward into the Dalton bay, the lake 

drained, forming the present Housatonic Eiver and cutting away much 

of the old delta. The sand which had rested against the ice caved to a 

terrace scarp sloping north toward the Dalton bay, traces of which 

scarp can be seen just north of the Catholic cemetery.

In Hinsdale one must mentally restore the level of Maple street, the
EMEBSOK.] POST-GLACIAL DEPOSITS. 97

broad plain east of the village, and carry it across to the hillside on the 

west of the village, in order to understand the great sand deposit, for 

brooks and temporary washouts have carried forward the destruction 

begun by the breaking away of the lake.

From the foot of the great delta front below the library a broad, flat 

plain of fine sand extends south, the whole width of the basin, to the 

foot of the transverse sand plain in the Washington Basin which bounds 

the lake on the south.

The plain descends slightly to the south and the river meanders 

slowly across its flat surface. The fine sands were being spread over 

the bottom while the great gravel delta was advancing into the basin 

and gradually covering them. The high delta flats at Hinsdale and at 

Washington Station and the lake bottom bed between them can be 

clearly made out from th*e contours on the inch-scale map.

DALTON KAMES.

A great kame starts high up ow the Wakonah Falls Brook in southwest Windsor. The broad, open valley is in its northern part and for a 

long way south bottomed by till, and is then suddenly covered by 

gravels which gain great thickness southwardly before they reach the 

reservoir 3 miles northeast of Dalton. Southeast of the latter place, 

in the northwest of Hinsdale, similar sands expand in a broad basin. 

These join the Windsor sands and extend west down the Wakonah 

Brook Valley into Dalton as a well-sorted gravel kame of large dimensions (a long sand plain abounding in deep pits) which winds strangely 

across Dalton and is finally submerged beneath the broad sand 

stretches which expand westward from the Pittsfield plains.

It is clear that these gravels began to be deposited when the ice still 

filled the Dalton depression, and that the waters that brought them 

had then an outlet south across Ashmere reservoir into the Hinsdale 

lake; that, as the ice lowered, the drainage of West Windsor and North 

Hiusdale ran southwest across the ice, by Wakonah Brook, into the 

Housatonic Valley. Later the horizontally stratified gravels were let 

down by the ice remnants on which they partly rested and sank to such 

a level that they were in places wholly, and in places only partially, 

submerged by the sands which were afterwards swept south through 

the Hoosac Valley and spread on the Pittsfield-Dalton Plain.

HIGH TEERACES IN BEOKET.

A high mountain ridge extends northwest from Becket Mountain, 

and for several miles is flanked by two great terraces, at 2,080 and 

2,000 feet, which seem to be the remnants of a glacial lake whose 

waters finally drained into Basin Pond Brook. These terraces can be 

reached by the blind road west of the reservoir. They have not been 

made the subject of special study. 

Bull. 159 7
98 GEOLOGY OF EASTERN-BERKSHIRE COUNTY. MASS. [BOLL. 159. 

HIGKE SANDS AT ENTRANCE TO EAST LEE VALLEY.

Standing on the hill south of Lee and looking across to the entrance 

of the East Lee Valley one sees that the whole broad mouth of the valley 

is clogged by exceptionally high, flat-topped sands, which project into 

the valley in great lobes. They have been notched by the cutting for 

a railroad that was never finished, and, as usual, have a cemetery on 

their flat surface. They represent the filling of a temporary lake, held 

up by the Berkshire Valley ice and drained southeast down the East 

Lee Valley.

DEFLECTED GLACIAL DRAINAGE DOWN THE HINSDALE, EAST LEE, 

AND TYRINGHAM VALLEYS.

Each of these long valleys has been greatly affected by the movement of the ice out of the Berkshire Valley, and by the deflection of 

the flood waters during the meeting of the ice.

From Hinsdale down the Westfield Eiver, from East Lee down the 

Farmington Kiver, and from Tyringham down the Clam Eiver, this 

influence is felt the whole length of the valleys and' out across the Connecticut Valley in Massachusetts and Connecticut. Bowlders of bluequartz gneiss are not rare here, while the " hardheads" of the Cambrian 

quartzite from the Housatonic Valley are everywhere very common.

MINERAL RESOURCES.

LIMESTONES.

Pre-Cambrian. The time has long past when the Hinsdale limestone 

was burned for quicklime. Most of it is too impure for architectural 

purposes. The limestone at the mouth of Coles Brook, in which the 

chondrodite grains have changed to pale yellow-green serpentine, is 

adapted to ornamental purposes, and the heavy bed, crossed by the 

Housatonic branch, southwest of Hinsdale is very pure and of even 

grain, firm and of good luster, and ought to be considered as a source 

of marble.

Silurian. The Stockbridge limestone or dolomite is quarried extensively for local uses in the deep bays which penetrate the HoosacEange 

in Dalton and Tyringham, and the important quarries south of Lee village have furnished large quantities of high-grade marble, from which 

the Washington Monument, the Capitol extension, Girard College, the 

new city hall in Philadelphia, and St. Patrick's Cathedral in New York 

City were built. It is a white, durable, but rather coarse marble, and 

cubes 20 feet on a side can be furnished from the quarries. It sustains 

the highest tests for crushing strength.
EMERSON.] MINERAL RESOURCES. 99

Analysis of white dolomite from Lee, Massachusetts.

.[G. P. Merrill: Cat. Nat. Mus., 1889, p. 505.]

Per cent.

54. 621

43. 932

.365

.610

Tests of strength of dolomite (marble) from Lee, Massachusetts, at Watertown Arsenal. 

[G. P. Merrill: Cat. Nat. Mus., 1889, p. 497.]

Size of cube.

5. 91+. ...........

5.92+............ 

5.92..............

5. 01+. ...........

5. 91+.... ........ 

5.90..............

5.89+............

6. 00+...... ...... 

5.90..............

5 QJ_

5. 91+. ........... 

5. 90J. ...... ......

5.93+............

5.93+............ 

5.93..............

5.92+............ 

5.92+............ 

5.91..............

Position.

JEiid..........

,

bed...........

.

bed.. .........

v

bnd ..........

»

bed. ..........

JEnd ..........

Strength 

per square 

inch.

22. 860

22. 900

21. 700

20. 504

22. 370

22. 820

Remarks.

(Sustained maximum load of testing 

I machine without apparent injury.

Flaked off along one edge.

Crushed suddenly with report.

Burst into fragments suddenly.

(Effect of loading, slight flaking of 

\ one face of block ; did not break.

[Sustained maximum load of testing 

< machine without perceptible inGRANITE.

Pre- Cambrian. The coarse gneisses of the pre-Cambrian series have 

been quarried for common work, like bridge building and underpinning, 

but have been used only locally.' They rust badly, and may crumble.

Cambrian. The conglomerate-gneisses are often so strongly metamorphosed that they become complete granites. This seems often to 

depend on their proximity to sharp upfolding of the pre-Cambrian rocks. 

The best quarry is that of the Chester Granite Company, in tlie southeast coruer of the Becket quadrangle. This granite is fine-grained and 

clear gray, a little too dark for polished work but taking a fine surface 

and furnishing large blocks of even grain and color, suitable for the best 

monumental work. A similar stone has been much worked in the Clark 

quarry, beside the railroad west of Coles Brook. Here the passage of 

the massive quarry stone into the common flaggy gneiss can be clearly 

seen. A promising quarry has been opened on N. Alderman's land, in 

the center of Becket, and in Otis the quantity of good granite is inexhaustible. In the south part of the area in New Marlboro and Norfolk 

a rock of the same age and character has been much quarried, especially on the east slope of Ball Mountain.
100 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

FLAGSTONES.

The Cheshire quartzite is mentioned by Hitchcock as furnishing the 

most perfect flagstones in the State. The best quarries were in the 

west part of Washington, 5 miles southeast of Pittsfield. Other quarries occur in Tyringham and Lee. Little work, however, seems to be 

done on these beds now.

BUHRSTONES.

In the same hill in Washington in which the flagstones occur buhrstones were formerly quarried which sold for $70 to $80 each. This 

industry also has passed away.

GLASS SAND.

Where the Cheshire quartzite extends far up into the mountains in 

Washington much glass sand is dug and carted down to the railroad. 

In the western part of Washington also and in the Gulf at Dalton much 

of the quartzite is pure enough for use in glass making.

ROAD MATERIAL.

In Hitchcock's Final Report on the Geology of Massachusetts (p. 211) 

is perhaps the first suggestion of a rock for road building in the State. 

The harder varieties of the Cheshire quartzite are thought to be well 

fitted for this purpose. It will certainly be the best local rock for this 

use, but the pure quartzite found in the Stockbridge limestone will be 

nearly as good. The Gulf in Dalton, the country in Washington south 

of Sackett Brook and east of New Lenox, the western ridge at Fernside 

in Lee, and the quarry just north of the river, together with the great 

hill nearly a mile east of Lee, will furnish material in abundance.

SOAPSTONE.

A large amount of soapstane has been taken out at the quarry beside 

the brook above Wakonah Falls in the south of Windsor, and recently 

the bed has been opened west of the old quarry and good, soft, slaty 

soapstone obtained. Along the same bed, a mile southwest, some work 

has been done on the hard, green, massive chlorite associated with serpentine. A pale-green, fine-grained steatite occurs in large amount as 

a selvage on the east of the great limestone bed cut by the east branch 

of the Housatonic in .the southeast of Hinsdale. This would form a 

beautiful rock for inside work.

IRON ORES.

The pre-Cambrian rocks are very rusty, especially in their upper 

strata, and have everywhere tempted mining. As this rustiness 

depends largely upon the decomposition of pyrite it is not a good indication of valuable ore. Considerable digging has been done just east 

of Hinsdale Center, at N. Alderman's in Becket, and at the Hotchkiss 

and Cleveland mines at New Marlboro. The principal ore is pyrrho-
EMERSON.] MINERAL RESOURCES. 101

tite. Nothing lias been found to justify expenditure. The Cleveland 

mine was first opened as a gold mine but latterly has been worked as 

a nickel mine.

GRAPHITE.

Considerable excavation has been made at the "lead mine" east of 

Washington Station, on the Lyman place, and openings have been made 

along the same band at several places to the north and at the creamery near Hinsdale. Graphite occurs in considerable amount ou Sky 

Hill in Tyriugliam and across Few Marlboro, but nowhere in sufficient 

quantity for mining.

GOLD AND COAL.

The Cleveland mine in New Marlboro was first opened as a gold 

mine. Buttons of gold and silver received from the assayers are shown 

by the owners. There is no probability that gold in paying quantity 

will be found within the limits of the area covered by the map. In 

my notebook are the priuted-out answers to the questions of a deaf old 

man living in the south part of Windsor, the sides of whose house were 

heaped with great blocks of rock full of rotted yellow mica, which he 

fondly believed to be gold. The rock had been quarried and brought 

down by him from the mountain to the east. I tried in vain to persuade him to waste no more labor on the search.

The following items appeared in the Springfield Eepublican:

. 1895. fellow Metal at Hinsdale. WoTk of mining gold at the Primrose farm at Hinsdale will begin in the spring. Assays have varied considerably, but all find gold in 

paying quantities. Ricketand Banks, of New York, have made three fire assays; Professor Suthphen, of Gloversville, New York, has made numerous assays, the last 

being of sand that yielded $56.33 per ton. A large syndicate in New York City is 

trying to buy a part of the Primrose farm. The interested capitalists live in Pittsfield. The Fleming farm, owned by George Duncan, of Middlefield, will soon pass 

into the hands of a syndicate of Springfield men if proper terms can be made.

August 15,1896. George M. French has a number of men excavating on his "gold 

find" preparatory to the final examination by Professor Suthphen, of Albany. Despite the contradictory statements made by different assayers Mr. French still has 

some hopes and flattering offers as well. The numerous assays made by reliable 

authorities do not agree. While some find gold in large quantities, others find little 

or no trace.

I have not visited the farm since the new mine was opened. My 

earlier study of all the ledges of the region had not led me to expect 

important gold deposits there. The following similar account is quoted 

for the interesting legend and note concerning the custom of selling 

mineral rights in the hill towns.

Long ago there was mining for gold done in that wild region known as "the Gulf," 

in Dalton, in a very desultory way, however, without capital and with no thoroughness, and by those not expert in prospecting.

The discoveries at Primrose farm have stimulated explorations and inquiry, with 

results that are surprising and may be important and profitable. We announced 

exclusively last week Mr. Duncan's purchase of the Fleming farm, which, it is
102 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

believed, contains a continuation of the Primrose "fissure," and the fact, that foreign capital was ready to invest upon assay proof of a good outlook. Mr. Corey, in 

the town of Washington, but near the Primrose, has had assays made from superficial rock contaminated or impregnated from the Primrose, and finds a yield of $11 

to the ton. The'William Pease farm, also in Washington, has shown such promise 

that it has been leased for prospecting and mining purposes by a syndicate from 

Lee W. H. Gross, E. Ely, and Mr. Davis, the latter said to be an experienced 

mine hunter.

That mineral wealth was suspected or believed to exist in these Washington farms 

is evident from the fact that thirty years ago farms were sold subject to the sellers' 

reserved right to prospect for and dig minerals. An instance of this is the L. A. 

Huban farm, owned by father and son, and comprising about 300 acres. This farm 

adjoins the Pease farm, we believe, leased, as stated, to Gross, Ely, and Davis, and 

overtures for its purchase by the individual or syndicate for whom Mr. Post is acting 

were made a good while since. It is only recently, comparatively, that the reservation as to minerals and mining was "bought off" by young Mr. Huban.

There is a legend lingering in the memories of men of Lenox and vicinity that, in 

the days of legend, an Indian, remnant of a tribe or a descendant of some family of 

these wandering original Americans, used to tell the white people about a coal deposit 

he knew of in the woods of Washington. This was before the days of railroads 

and coal sheds, and when wood was the only and abundant fuel. It is even related 

that a bottle of "fire water" was offered as a test to prove the assertions, the Indian 

to have the drink if he brought a pail of coal to Lenox Dale, as he said he could. 

He was watched, the white man then as now intending to get the best of the Indian, 

by discovering his secret, but he was too smart for the watchers. He slipped off in 

the night and returned in the night, bringing the pail of coal. Mr. Hubaii believes 

this coal mine is on his farm.

While he was plowing in one of his fields last May he turned up several lumps of 

coal; a piece of it is now on the Sun's desk. Mr. Huban has owned the place about 

thirty years, and there has been no such use of coal about the farm as should make 

its presence probable or even possible. He has done no prospecting, made no 

examinations to speak of, but is satisfied in his own mind that there is a coal 

deposit where the outcroppings were struck with the plow.

Of course there is not the slightest possibility of finding coal in 

Washington, and the prospect of discovering gold in paying quantities 

is scarcely better. More than fifty years ago President Hitchcock published in his final report a long list of similar legends and foolish 

searches for gold, in the hope that the tendency to waste money in 

that direction might be checked with increase of knowledge. I do not, 

however, find any apparent decrease in the number of "gold mines" in 

the region.
U.S.GEOLOGICAL SURVEY". BULLETIN NO. 159 PL. IX

LEGEND

Rowe 

ScWst

ILoosac. 

Schist.

OuaHzilein 

Stpckbridge 

Limestone

Stockb ridge 

Limestone

Phyllite al the

top of Cheshire

Quartzite

I

Cheshire 

Quartzite

Aw

Washington

Hinsdale 

Limestone

| Ah ]

Hiiis dale 

Gneiss

Faults

A.Hoen t Co.Lifh.BaltonoreGEOLOGY OF THE EASTERN HALF OF THE HOUSATONIC QUADRANGLE

BY B.K.EMERSON 

1897

Scale of miles

I 0 I 2 3 4 S

Contour Interval 100 feet
A MINERAL LEXICON OF EASTERN BERKSHIRE COUNTY, 

MASSACHUSETTS.

The region covered by this lexicon embraces the towns of Windsor, 

Dalton, Hinsdale, Becket, Lee, Tyringham, Otis, Sandisfield, and New 

Marlboro.

An attempt has been made to give a full chronological history of each 

mineral, its geological age and distribution, and its mineralogical 

varieties and crystalline form. All sections which are not followed by 

citations are by the author. The greater portion of the material 

studied is contained in the collection of Mr. Daniel Clark, of Tyringham, 

and where it is not otherwise stated it may be assumed that the best 

illustration of every mineral in the county is to be found there.

ALB1TE. 

1891. Albite. New Marlboro.

A beautiful albite in good crystals a half inch long, showing a fine moonstone effect in unusually deep blue on the face M (010). It occurs in preCarnbrian gneiss at the Hotchkiss mine, associated with pyrrhotite and 

pyroxene. The crystals are limpid and free from inclosures, as seen 

under the microscope, and the opalescence is due to the cleavage on OP 

(001). It extinguishes in plates cut parallel to M at +14° 21', and is thus 

an albite.

1895. Albite replaced by quartz. Tyringham (Sodom).

Pre-Cambrian. See page 52 for a description and illustration of this 

remarkable pseudomorph, which retains the twin striation and pearly 

luster with great perfection.

ALLANITE.

1852. Gadolinite. Becket.

C.U. Shepard: Treat. Min.; p. 253. This is probably the allanite from 

the pre-Cainbrian gneiss.

1876. Allanite. Becket.

C. U. Shepard: Cat. Min. within 50 miles of Amherst, p. 7.

1890. Allanite. Becket. Hiusdale. Dalton. Washington. Otis. 

Tyriugham. Sandisfield.

Allauite is everywhere found in scattered crystals of small size in the 

Washington (pre-Cambrian) gneiss. Its small pitch-black crystals, with 

dark reddish decomposition borders and the slight puckering of the fracture in the inclosing gneiss which radiates from, each crystal, are very 

characteristic of the rusty pre-Cambrian gneisses. The best localities are 

on the brook south of the Daltou clubhouse and opposite D. dark's house 

in Tyringham.

103
104 GEOLOGY OF EASTERN BERKSHIRE COUNtY, MASS. [BULL. 155.

AMPHIBOLE.

1823. Asbestos. Windsor (near Cummington soapstone quarry). 

Asbestos adhering to actinolite. 

J. Porter: Min. Loc., Am. Jour. Sci., Vol. VII, p. 252.

1824. Black hornblende. Washington.

Well crystallized.

J. Porter: Am. Jour. Sci., Vol. VII, p. 253.

1824. Tremolite. . New Marlboro.

E. Hitchcock: Geol. of a part of Mass., Am. Jour. Sci., Vol. VIII, p. 35.

1824. Tremolite. New Marlboro. Pittsfield. Lee.

New Marlboro; Pittsfield; in dolomite, bladed, granular. 

 Lee; fibrous, fibers more than 2 feet long. 

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 46.

1825. Tremolite. Lee.

Above cited.

S. Robinson: Cat. Am. Min., p^55.

1825. Tremolite. New Marlboro.

S. Robinson: Cat. Am.Min., p.63.

1825. Actinolite.

(The article under 1823, above, is cited.)

The actinolite is found in the north part of the town in large, elegant 

crystals, which are fasciculate, radiate, or intermixed (J. Porter). 

S. Robinson: Cat. Am. Min., p.77.

1825. Hornblende. Dalton.

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p.43.

1828. Hornblende. Dalton. Becket.

Rock var. slate. East part of Becket, granitic.

Amos Eaton: Geological Nomenclature, Am. Jour. Sci., Vol. XIV, p. 145.

1832. Hornblende. Litchfield County, Connecticut. Sheffield and 

Great Barrington, Massachusetts.

White crystals, more than an inch long and three-fourths of an inch wide, 

but much flattened, abound throughout the dolomite of Litchfield County, 

Connecticut, particularly at Canaan; they are also found under similar 

circumstances farther north into the borders of Massachusetts, at 

Sheffield aud at Great Barrington.

C. U. Shepard: Treat. Min., Vol. I, pt. 2, p. 266.

1841. Tremolite. Tyriugham. Lee. 

In dolomite.

E. Hitchcock: Final Rept.,585. 

No. 537, Catalogue of State collection, p, 809.

1844. Actinolite. (Augitus proteus.) Windsor.

J. D. Dana: Sys. Min., 2d ed., p.439.

1844. Tremolite. (Augitus pr.oteus.) Lee (east part). 

Excellent specimens. 

J. D. Dana: Treat. Min., 2d ed.,p. 371.

1858. Tremolite. Becket (southeast part).

Dolomite with tremolite. E. Hitchcock: No. 187 under limestone in Sixth 

Ann. Rept. Bd. Agri. Mass., Appendix, p. xxxv. Large masses of loosely 

aggregated and coarse-bladed tremolite, probably from the south end of 

the Coles Brook pro-Cambrian limestone.
fcMERSON.] MINERAL LEXICON. 105

1868. Actinolite. Windsor. Lee.

Specimen from Lee is radiated.

J. D. Dana: Sys. Min., 5th ed., p.241.

1868. Tremolite. Lee (1£ miles southwest of meetinghouse).

Idem, 5th ed., p. 241.

1892. Actinolite. Windsor. Lee.

Specimen from Lee is radiated.

J. D. Dana^ Sys. Min., 6th ed., p. 1060.

1892. Tremolite. Lee.

Cited as in 1868.

J. D. Dana: Sys. Min., 6th ed., p. 397.

1894. Tremolite. Lee.

In Stockbridge limestone. In separate blades and in long radiate 

sheaves. The bladed type was abundant in the old Gross quarry and 

went down to a great depth, spoiling a large quantity of stone. Specimens are found in every collection.

1895. Asbestos. Lee.

In Stockbridge limestone. As felted paper-asbestos in thin white sheets 

several inches across and as fibrous radiated masses near the Hobbs place 

in South Lee. D. Clark collection.

1895. Tremolite. Tyringham (Sodom, below Hop Brook gorge).

In broad, radiate, columnar masses as large as one's fist, made up of pale 

greenish gray needles 2 to 3 inches long derived from white pyroxene. 

Also in finest needles shooting through limpid quartz. Pre-Cambrian. 

D. Clark collection.

1895. Tremolite. Monterey (Bear Mountain).

In pro-Cambrian. Straight, fibrous, pale-green to white asbestos fibers 

3 to 4 inches long. D. Clark collection.

1895. Actinolite. Tyringham (Hop Brook gorge).

In pre-Cambrian limestone. Black to dark-green actinolite in matted 

blades grown through orthoclase, and broad parallel-bladed masses several 

inches in length, making very beautiful specimens. It grows around 

weruerite and causes the bending of the crystals.' D. Clark collection. 

1895. Hornblende. New Marlboro (on road to Southfield, at deep 

excavation by roadside, in the very rusty rock).

Pre-Cambrian. Cavities are filled with black hornblende crystals 1| 

inches long; bladed, well terminated, simple forms. D. Clark collection.

1895. Hornblende. Monterey (Bear Mountain).

Pre-Cambrian. In green, massive hornblende rock, fine, stout, black 

crystalsooP( 110), ooPoo (010), ooPoo (100), P (111), OP (001).

1895. Tremolite. Tyringham (the Cobble).

Fine, radiating snow-white tremolite in the Stockbridge limestone at the 

foot of the mountain. D. Clark collection.

1895. Hornblende. Tyringham (the Cobble).

Pre-Cambrian. Fine jet-black crystals in the garnet biotite rock, with 

ilmenite above the limestone. D. Clark collection.

1896. Actinolite. Becket (one hundred rods east of E. Alderman 

and son's house).

In the Hinsdale (pre-Cambrian) limestone in large, pale-green, compact 

masses and iu loosely interwoven aggregates of coarse blades of rich 

green color shading to brown.
106 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

1896. Actinolite. Otis.

The coarse pre-Cambriau limestone at Otis Center contains an emeraldgreen bladed actinolite with scapolite.

1896. Hornblende.

A black fibrous hornblende is an abundant constituent of the Lee gneiss 

(p. 33), and of the amphibolites which occur in the Becket gneiss.

APATITE. 

1841. Phosphate of lime. Hinsdale.

In mica-schist. E. Hitchcock: Final Report of Geol. of Mass., p. 604. 

1844. Apatite. (Fluellus hexagonus.) Hinsdale.

J. D. Dana: Sys. Min., p. 238. 

1868. Apatite. Hinsdale.

Sparingly. Idem, 5th ed., p. 553.

1892. Apatite. Hiusdale.

Idem, 6th ed., p. 767. This locality can not be recovered. 

1895. Apatite. Tyringham (Sodoin, below Hop Brook gorge.)

In pale-green hexagonal prisms half an inch long in white orthoclase, 

from the Hinsdale (pre-Cambrian) limestone. D. Clark collection.

AKAGONITE.

1895. Aragonite. New Marlboro (road to Southfield, at a deep cut in 

rusty rock by roadside).

In pre-Cambrian rocks, but of late formation. In fine tufted masses of 

yellow crystalline blades and needles. D. Clark collection.

BAEITE. 

1890. Barite. Becket (east of Shaw Pond).

Bowlders from the Hinsdale (pre-Cambrian) limestone, with galena and 

chalacopyrite. In bladed masses.

BERYL.

It is remarkable that there is no beryl in Berkshire.

BIOTITE. 

1895. Biotite. Tyringham (the Cobble).

Broad wrinkled sheets of black biotite 2 to 3 inches across, probably 

pre-Cambrian, from Sky Hill above the Cobble. D. Clark collection.

1895. Biotite. Tyringham (Hop Brook gorge).

In pre-Cambrian rocks. Magnificent crystals were obtained by Mr. 

Clark from the rotten zeolite vein in the limestone; great perfect crystals, 

with polished faces, hexagons 5 inches by 4£ inches and 3 inches thick. 

Other crystals were tapering, 3 inches at the base and 1£ inches high. 

- Very many other great crystals were compressed at the edges, often regularly at all the edges, into perfect saucers. The faces of the vertical zone 

were often coated by a thick layer of the white, velvety, globular sphaerostilbite, forming specimens of great beauty. Smaller prisms, often an inch 

in length, grow out from the larger ones. A strongly developed parting 

often divides the great crystals into long prismatic forms. Many crystals 

had fallen in the cavities, where they formed and are cemented by the 

sphterostilbite. Many have changed to jefferisite, q. v.
KHERSON.] MINERAL LEXICON. 107

CALCITE. 

1814. Elastic marble. Pittsfleld.

" On taking up one of these stones, from a quarry near Pittsfield, which 

was just prepared for a gravestone, about 4 feet high and 2 feet wide, 

I was much surprised at the tremulous motion which I perceived." It 

bent with the least pressure, but recovered itself without the smallest 

change or crack. Only a few specimens were elastic. They were grayish 

white, foliated, granular, and effervescent.

W. Meade: Mineralogical notice respecting elastic marble from Massachusetts.

A. Bruce: Am. Min. Jour., Vol.1, p. 93.

1814. Elastic marble.

A polished slab 2 feet long and 1 inch thick, dried near the fire, lost its 

elasticity, which was immediately restored by wetting. Wm. Meade: 

letter.

Am. Min. Jour., Vol. I, p. 267.

1832. Limestone. New Marlboro.

Gray, CaC03, 98 per cent; residue, chiefly mica, 2 per cent marble. 

Abundant; production cited from Dewey. Mill for sawing in New Marlboro. 

E. Hitchcock: Geol. Mass., Am. Jour. Sci., Vol. XXII, pp. 26,38.

1895. Calcite. Lee.

In Stockbridge limestone. In a rare geode cavity and perched upon fine 

dolomite rhombs (see under Dolomite), is a beautiful crystal half an inch 

long, having the faces R (1011), rounded by iR3 (2134) and iR (Oli2), R 

(1010), R5 (3251), R3 (2131).

D. Clark collection.

1895. Marble. Tyringham.

Bowlders. White marble, gray banded marble, black faulted marble. 

D. Clark collection.

1895. Stalactite. Tyringham (the Gobble). 

In the Stockbridge limestone 

D. Clark collection.

1895. Calcite. Tyringham (Hop Brook).

Pre-Cambrian; very coarse crystalline vein stones, fine gray, pink, plum 

color, and white; shot through with hornblende crystals, crusted with 

limpid calcite crystals oo R (1010), £R (Oll2), 4R (4011).

CHABASITE. 

1895. Chabasite. Tyringham (Hop Brook gorge).

In pre-Cambrian limestone. Massive and in rhombohedra R (1011), |R 

(0112), with polished faces 5 mm. across. Green actinolite is intergrown 

with it. Twins; twinning plane=R. Nearly opaque white.

D. Clark collection.

CHALCOPYEITE. 

1890. Chalcopyrite. Becket (east of Shaw Pond).

In bowlders from pre-Cambrian limestone with galena and barite.

1893. Chalcopyrite. Becket (east of Center Pond on farm of M. J. 

Alderman).

Vein worked 1 inch wide. Associated with pyrite, pyrrhotite, and calcite in hornblendic gneiss of pre-Cambrian age.
108 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

CHONDRODITE. 

1841. Augite. Lee.

"Within 2 miles of Lee we meet with limestone which often contains a 

mixture of augite, and this mineral being decomposed at the surface yet 

projecting beyond the limestone the whole rock exhibits a brown, very 

irregular aspect."

E. Hitchcock: Final Kept., p. 627.

1885. Chondrodite. Hinsdale. Monterey.

Noted as occurring in limestone at the Hinsdale railroad station and in 

bowlders between South Lee and Monterey. 

. J. D. Dana: Am. Jour. Sci., Vol. XXIX, p. 208.

1887. Chondrodite. Hinsdale. Lee.

Hiusdale; in village (on railroad) and southwest of the village, west of 

the railroad.

East Lee; on the high hill between the two valleys coining in from the 

east, molasses as large as one's fist; also on the opposite side of the valleyto the northwest, and in the bottom of the valley a mile east of East Lee.

J. D. Dana: Am. Jour. Sci., Vol. XXXIII, pp. 275, 276.

1892. Chondrodite. Lee.

In crystalline limestone in East Lee.

J. D. Dana: Sys. Min., 6th ed., pp. 1059, 541.

1895. Chondrodite. Becket. Middlefield.

100 rods east of R. Alderman and son's house, in Becket Center, in a 

Hinsdale pre-Cambrian limestone band 5 rods wide.

It occurs in red grains, and is especially abundant in a large bowlder 

100 rods northeast of the ledge. Also in Coles Brook, across Becket and 

Middlefield, especially at the cut at the mouth of Coles Brook, where it is 

changed to pale-yellow serpentine.

1895. Chondrodite. Hinsdale. Tyringham. Lee.

Iii especially large masses, of dark red color, partly changed to chlorite 

at 0. Bill's, by the roadside, a half mile north of Muddy Pond, in Hinsdale, and on the high, bare hill etast of the hotel at East Lee.

CLINOOHLORE.

1895. Clinochlore. Tyringham. Great Barrington.

On Bear Mountain, in matted scales half an inch across, with garnet on 

a fine-grained biotite-gneiss of pre-Cambrian age.

OYANITE.

1896. Cyanite. Becket.

Gray blades, containing small, regular garnets, centrally filled with dark 

grains, and changing to muscovite. See PI. I, p. 26.

DOLOMITE. 

1821. Dolomite. Lee.

Is fetid. Most of that called limestone in the county is dolomite. 

C. Dewey: Am. Jour. Sci., Vol. Ill, p. 239.

1824. Dolomite. Lee. Pittsfield. New Marlboro.

In latter place contains augite as well as tremolite.

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 35.
EMEESON.] MINERAL LEXICON. 109

1825. Dolomite. New Marlboro.

With augite and tremolite.

E. Hitchcock: Geol. of part of Mass., Am. Jour. Sci., Vol. VIII, p. 35.

S. Robinson, Cat. Am. Min., pp. 55, 63.

1854. Dolomite with tremolite. Becket (southeast part).

E. Hitchcock: Sixth Ann. Rept. Mass. Bd. Agri., Appendix, p. xxxv, No. 

187.

Contains much rather flne-bladed tremolite; is probably from a bowlder 

of the Stockbridge limestone.

1876. Dolomite. Hinsdale. Lee. Lenox.* Stockbridge.

C. U. Shepard: Cat. Min. found within 50 miles of Amherst, p. 3.

1895. Dolomite. Lee.

In a large drusy cavity from the quarry in the village, in Stockbridge 

limestone. Rhombs up to an inch on a side, and in other cavities up to 

3 inches. Perfectly limpid, and with polished and perfect faces, piled 

loosely on each other. Some of the rhombs are expanded to broad, flat 

plates. In others are phantom crystals, containing eccentric, smoky 

kernels; that is, on a smoky translucent rhomb, half an inch across, is a 

regular transparent increment two-sixteenths to three-sixteenths inch 

thick, which is applied only to the three faces adjacent to a lateral solid 

angle. A complex rhombohedral crystal of calcite half an inch long (see 

under. Calcite) is perched upon one of the rhombs, making a cabinet 

specimen of rare beauty. 

D. Clark collection.

EPIDOTE. 

1825. Epidote. Windsor.

In prismatic crystals in quartz, also granular in hornblende rocks (H. 

M. Wells). 

S. Robinson: Cat. Am. Min., p. 77.

1825. Epidote. Dalton.

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 43.

1841. Epidote. Hinsdale.

In mica-schist.

E. Hitchcock: Final Rept., p. 606.

1895. Epidote.

Epidote is everywhere a characteristic constituent of the Hinsdale 

gneiss, but it rarely occurs" in sufficient quantities and depth of color to 

form cabinet specimens. The best place to find it in any quantity is in 

the river, behind the stone mill in Dalton.

FIBEOLITE.

1824. Fibrolite? Becket (Becket).

Minute fibers, dark, hard, infusible, rare.

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 40.

1825. Fibrolite.

Cited in Robinson's Catalogue. (I have found no fibrolite in Becket.)

1892. Fibrolite. Norfolk, Connecticut.

On Tobey Hill and in bowlders to the south, nodules of feldspar and 

quartz more or less changed to muscovite and fibrolite. Thin section 

described mica arranged in twinning planes of feldspar. 

Wm. H. Hobbs: Pseudoniorphs after feldspar, Am. Geologist, Vol. X, p. 46.
110 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159. 

1895. Fibrolite. Otis. Saudisfield.

Commencing with Filley Mountain m Otis, nbrolite becomes gradually 

an important constituent of the pre-Cambrian gneiss across Sandisfield 

and into Connecticut.

1897. Fibrolite. New Marlboro. Norfolk, Connecticut.

The nodular gneiss that extends from Campbell Falls in New Marlboro 

to Norfolk Center contains abundant nbrolite in the mnscovite nodules.

GADOLINITE.

1852. G-adolinite. Becket.

C.U. Shepard: Treat. Min., p. 253. 

See Allanite.

GALENA. 

1896. Galena. Becket (east of Shaw Pond).

In bowlders from pre-Cambrian limestone, with barite and chalcopyrite.

GABNET.

1858. Pyrope. Sandisfield.

E.Hitchcock: Cat. State Coll., Mass. Agri. Kept., p. 52, No. 161. (Isa 

common iron garnet in Tyringham gneiss.)

1895. Garnet. Tyringham (pasture of Eiverside Farm).

In white mica-schist of Cambrian age, forms oo O (110), 202 (112), rich 

red-brown. Also on the Cobble in deep red crystals an inch across in 

biotite.

D. Clark collection.

1895. Garnet. Monterey (Bear Mountain).

In coarse, white, shining hydromica-schist. Red crystals nearly threefourths inch across oo P (110).

GRAPHITE.

1823. Graphite. Hinsdale.

J. Porter: Am. Jour. Sci., Vol. VI, p.248.

1824. Graphite. Hinsdale.

Foliated and granular with augite, nearly slaty, in considerable quantity. 

C. Dewey: Geol. western Mass., Am. Jour. Sci., Vol. VIII, p. 54.

1824. Graphite (black lead). Hinsdale.

With augite, foliated and massive.

C. Dewey: Hist. Berkshire County, p. 197.

1825. Graphite.

S. Robinson: Cat. Am. Min., p.54.

1825. Graphite. New Marlboro.

In great abundance.

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 43.

1825. Graphite. New Marlboro.

E. Hitchcock: Geol. of part of Mass., Am. Jour. Sci., Vol. VIII, p. 54.

1825. Graphite.

Above cited. S. Robinson: Cat. Am. Mm., p. 63.
EMERSON.] MINERAL LEXICON. Ill

1832. Graphite. Hinsdale.

E. Hitchcock: Geol. Mass., Am. Jour. Sci., Vol. XXII, p. 47.

1833. Graphite. Hinsdale. New Marlboro. 

E. Hitchcock: Kept. Geol. Mass., p. 395.

1841. Graphite. New Marlboro. Hinsdale. Washington (1 mile northeast of deep cut at summit level Lyman's opening). 

E. Hitchcock: Final Rept., p. 240.

1844. Graphite (Plumbago scriptoria). Washington. 

J. D. Dana: Sys. Min., 2d ed., p. 539.

1868. Graphite.

Idem, 5th ed., p. 770.

1892. Graphite.

Idem, 6th ed., p. 1060.

1895. Graphite. Monterey (Bear Mountain).

In pre-Cambrian rock. In large masses on top of Sky Hill, with tremolite in blue-quartz gneiss. 

D. Clark collection.

1897. Graphite. Hinsdale.

The mineral is everywhere characteristic of the pre-Cambrian gneiss, 

and openings for mining have been made at three places in the town near 

the creamery, east of the center; near A. Walkin's house, in coarse salite 

rock; and in an extensive opening at the mine on the Lyman place above 

Muddy Pond, east of Washington Station.

HEMATITE. 

1890. Hematite. Hinsdale.

In masses of imperfect flat crystals associated with fine quartz crystals. 

Min. Coll. of E. B. Underbill, Hallock Mills, N. Y. Presented to Amherst College, 1888.

1895. Micaceous iron. Dalton.

In Cambrian quartzite. An aggregate of warped plates in white quartz. 

D. Clark collection.

HETJLANDITE. 

1895. Heulandite. Tyringham (Hop Brook).

Crystals 1 mm. long, implanted on hornblende and showing the faces 

ooPob (010), 2 Roo (201), OP (001). D. Clark collection.

ILMENITE.

1895. Ilmenite. Tyringham (the Cobble).

Abundant in broad plates an inch square in a quartz vein in a biotite 

garnet rock; also in other quartz veins 2 inches square one-fourth inch 

thick, in twisted plates; also in a mass from the drift, part of a large 

crystal 1 inch thick and 4 inches square.

D. Clark collection.

1897. Ilmenite. Dalton (Day Mountain).

«. In a lens of coarse granular orthoclase in a muscovite-gneiss full of 

needles of black tourmaline. It occurs in broad curved lamelUo half an 

inch thick. Collected by Mr. B. F. Newell, of Dalton.
112 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

JEFFERISITE. 

1895. Jefferisite. Tyringham (Hop Brook gorge).

The great crystals of black biotite at times change to a pale-yellow 

Jefferisite.

D. Clark collection.

LAUMONTITE. 

1895. Laumontite. Tyringham (Hop Brook).

White square prisms, 20 mm. long, 3 mm. across, and truncated by the 

usual oblique face. Abundant, but changing easily. 

D. Clark collection.

LIMONITE.

1822. Compact brown oxide of iron. Dalton.

Incrusting rocks.

P. Cleaveland: Min., p. 607.

1824. Fibrous brown hematite. Hinsdale (southwest of town and 4 

miles from Pittsfield).

Cement of conglomerate, often half an inch thick. 

C. Dewey: Geol. western Mass., Am. Jour. Sci., Vol. VIII, p. 18.

1825. Fibrous brown hematite.

Above cited.

S. Robinson: Cat. Am. Mm., p. 54.

1825. Limonite.

Article cited under 1822.

S. Robinson: Cat. Am. Min., p. 47.

1825. Iron, compact brown oxide. Pittsfield.

Breccia, with cement of brown oxide, hematite, and carburet of iron, 

interstices lined with minute quartz crystals.

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 43.

The origin of these limonites cementing the Cambrian breccias is given 

on page 80.

1828. Hematite. Dalton (3 miles south of village).

A. Eaton: Geol. Nomenclature, Am. Jour. Sci., Vol. XIV, p. 150.

1830. Hematite. Dalton (3 miles south of village).

A. Eaton: Geological Text Book, p. 34.

1832. Limonite. Hinsdale.

At Hinsdale the fibrous variety occurs as a cemeut to a fragmentary 

quartz rock. 

C. U. Shepard: Treat Min., Vol. II, pt. 1, p. 15.

1838. Hematite iron ore (limonite). Tyringham.

Several hundred tons dug in south part of the town. 

E.Hitchcock: Econ. Geol., p.126.

1841. Brown hematite. Tyringham. .

Several hundred tons said to have been dug in the south part of the 

town. Indications of extensive beds. 

E. Hitchcock: Final Rept., p. 197.

1844. Brown iron ore (Siderus Jiwmaticus). Hinsdale.

Cement in quartz rock.

J. D. Dana: Sys. Min.; 2d ed., p. 449.
EHEBSON.] MINERAL LEXICON. 113

1852. Limonite. Hinsdale.

At Hinsdale the fibrous variety occurs as a cement to a fragmentary 

quartz rock. 

C. U. Shepard: Treat. Min., p. 277.

1868. Limonite.

Idem, 5th ed., p. 173.

1892. Limonite.

Idem, 6th ed., p. 1059. 

Cited only in locality list.

MAGNETITE. 

1825. Magnetic oxide of iron. Windsor.

In octahedra (J. Porter).

S. Robinson: Cat. Am. Min., p. 77.

1841. Magnetic oxide. Tyringham.

Vein 4 inches wide in quartz rock on Bear Mountain, near the road to 

Beartown. 

<., E. Hitchcock: Final Kept., p. 194.

1895. Magnetite. Tyringham (the Cobble).

In white Cambrian gneiss, in imperfect crystals an inch across. 

D. Clark collection.

MELANTERITE. 

1824. Sulphate of iron. Tyringham.

In loose earth near Shaker Village.

C. Dewey: Hist. Berkshire County, p. 196.

MICROCLINE. 

1895. Microcline. Tyringham (south side of Hop Brook Valley).

Large cleavage pieces of flesh color, with fine perthitic banding of albite. 

D. Clark collection.

MUSCOVITE. 

1822. Mica. Hinsdale.

It occurs green (J. Porter).

P. Cleaveland: Min., Vol. II., p. 777.

1822. Prismatic mica. Hinsdale.

On the edges of common mica.

C. Dewey: Am. Jour. Sci., Vol. V., p. 399.

1825. Prismatic mica.

Above cited.

S. Robinson: Cat. Am. Miu., p. 53.

1895. Muscovite. Tyringham (the Cobble).

In good crystals. 

D. Clark collection.

NATRON.

1824. Carbonate of soda. Pittsfield (in springs).

C. Dewey: Geol. of part of Mass., Am. Jour. Sci., Vol. XIV, p. 32.

1825. Carbonate of soda.

Above cited.

S. Kobinson: Cat. Am.Min., p.65, 

Bull. 159 8
114 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BOLL. 159.

OLIGOCLASE. 

1895. Oligoclase. Monterey (Bear Mountain).

Starting from a point east of Fernside and going south half a mile up 

the side of Sky Hill. The crystals occur in a green, massive hornblende 

rock. They are an inch long, of cubical habit and dark flesh color, and 

show the faces ooPoo (010), oo'P(llO), ooP'(HO), ooP'3(130), oo'PS(l30), 

P,(T10), P(I11), 2^66 (201), 3,Pdo(201), Fob (101), 2P,(221). They show 

a fine striation over all the faces in the zone of b; there is a beautiful blue 

play of color on oo P ool, like Friedricksviirn oligoclase.

OETHOOLASE.

1832. Feldspar.. Middlefield. Becket.

The crystals are often deeply embedded in calcareous spar. 

C. U. Shepard: Treat. Min., Vol. I, pt. 2, p. 203.

1895. Orthoclase. Becket (100 rods east of E. Alderman and son's).

In pre-Cambrian limestone. In stout opaque-white crystals up to an 

inch long, some elongate in the direction of the prism and terminated by 

O (001) and Poo (101), and some having 0 (001) and oo Poo (010), forming a 

square prism terminated by ooP(HO) and Pob(TOl). Shows a fine blue 

opalesceuce. The same property appears in the feldspar of the coarse 

granitoid rock adjoining the limestone at the Coles Brook cutting.

1895. Orthoclase. Tyringham (John Winthrop pasture, south side 

upper Tyringham Valley).

From the pre-Cambrian. A white orthoclase, in good crystals of simple 

form with pyroxene. 

D. Clark collection.

1895. Orthoclase, var. loxoclase. Tyringhara (one-fourth mile southwest of D. Olark's).

In red-brown forms, resembling those from Hammond, New York. PreCambrian, associated with pyroxene. 

D. Clark collection.

1895. Orthoclase. Tyringham (Hop Brook gorge).

In pre-Cainbriau rocks. Greatly etched crystals in chesterlite form. 

D. Clark collection.'

V

1895. Orthoclase. Tyringham (Sodom, foot of Long Mountain and 

Hop Brook gorge). '

Drusy surfaces of small crystals, often with limpid ends and rounded 

faces, also in opaque, well-formed crystals ooP (110), OP (001), Poo (101), 

2 Poo (£01). Shows fine blue opalescence. Is associated with black, 

bladed hornblende in Hop Brook, and with white pyroxene and tremolite 

at the other localities, and is often full of square cavities, from which 

wernerite crystals have been removed. Pre-Cambrian.

D. Clark collection.

1895. Orthoclase. New Marlboro (road to Southfield, at digging in 

rusty rock by roadside).

Pre-Cambrian. Many fine crystals an inch long, of simple exterior forms 

oo P (110), oo Poo (010), Poo (101), 2Poo (201), oo P3 (210), P (ill); fine 

blue opalescencej color, opaque-white.
EMERSON.] MINERAL LEXICON. . 115

OPAL.

1825. Opal, hyalite, cacholong, siliceous sinter. Dalton. 

In masses of hornstone. 

C. A. Lee : Min. Loc., Am. Jour. Sci., Vol. IX, p. 43.

1890. Opal. Sheffield.

Common opal.

G. F. Kunz : Gems and Precious Stones of the United States.

PHLOGOPITE.

1895. Phlogopite. Tyringham (Hop Brook).

In many small crystals in wernerite. In pre-Cambrian limestone. 

D. Clark collection.

PYEITE.

1824. Pyrite. Lee.

v In compact masses.

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 55.

1825. Pyrite.

Above cited.

S. Robinson : Cat. Am. Min., p. 55.

1895. Pyrite. Tyringham.

One-fourth mile southwest of Mr. D. dark's house, at the head of the

 Tyringham Valley. In vein quartz of pre-Cambrian age. In fine crystals one-fourth inch across, superficially changed to limonite 0 (111),

D. Clark collection.

Also in bowlders in village 50 rods west of post-office perfect crystals 

changing to limonite in a quartz rock full of dolomite, 2 to 3 mm. long

f

20 <xf| 

 9 Tt (210). Also at Sodom, below Hop Brook gorge, in

finely polished crystals 1 to 15 mm. across changed to limonite. 

D. Clark collection.

PYEOLUSITE. 

1825. Manganese. Pittsfield.

The compact brown oxide, in considerable quantities. 

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 42.

1895. Dendrite. Tyringham (in gorge above Eiverside farm).

Beautiful forms in Cambrian quartzite. As they are in the red and black 

colors, they are in large part iron oxides. 

D. Clark collection.

1895. Pyrolusite. Monterey (near Bidvvell place).

Wavy plumose forms in yellow jasper. 

D. Clark collection.

1895. Dendrite. Dalton.

Bowlder in white Cheshire quartzite.

PYBOXENE.

1824. Ancite. New Marlboro.

Rough white crystals in limestone (doubtless white pyroxene). 

C. Dewey: Hist. Berkshire, p. 194. 

(Manifest misprint for augite.)
116 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

1824. Augite. Hinsdale.

With graphite.

C. Dewey: Hist. Berkshire, p. 197.

1824. Augite. New Marlboro. Hinsdale.

NewMarlboro; white four, six, and eight-sided prisms. Hinsdale; with 

plumbago, greenish gray, brown, yellowish, in crystalline forms. 

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 47.

1824. Augite. Hinsdale.

With graphite, as at Ticonderoga.

C. Dewey: .Geol. western Mass., Am. Jour. Sci., Vol. VIII, p. 48.

1825. Augite.

Same cited.

S. Robinson: Cat. Am. Min., p. 54.

1825. Augite. Pittsfield. Dalton. New Marlboro. 

Principally massive. 

C. A. Lee: Min. Loo., Am. Jour. Sci., Vol. IX, p. 43.

1825. Augite. NewMarlboro

E. Hitchcock: Geol. part of Mass., Am. Jour. Sci., Vol. VIII, p. 35.

1825. Augite.

Above cited.

S. Robinson: Cat. Am. Min., p. 63.

1841. Augite. New Marlboro. Tyringhara.

NewMarlboro; green augite in dolomite. Tyringham; white augite in 

dolomite.

No. 236 Catalogue, p. 809. 

E. Hitchcock: Final Rept.,p.569.

1844. Pyroxene. (Augitus diatormis.) Tyringham.

Cited only under localities.

J. D.Dana: Sys.Min.,2d ed.,p.539.

1852. Scapolite.

The canaanite of Hitchcock (from Canaan, Conn.), which is an exceedingly tough, compact, grayish white mineral, and contains ail. 53.36, perox. 

iron 4.09, alum 10.38, lime 25.80, mag. 1.62, carb. acid 4.0 (99.67)

C.U. Shepard: Treat. Min., p. 178.

1852. Scapolite. (Canaanite.) Canaan, Conn.

 Si03 53.36, FeO 4.09, A1303 10.38, CaO 25.80, MgO 1.62, CO, 4,99.67. 

Analysis by S. L. Dana. 

C.U. Shepard: Treat Min., p. 178.

1868. Pyroxene.

J. D. Dana: Sys. Min., 5th ed., p. 770.

1885. Pyroxene. Tyringbam.

A white, compact, fibrous pyroxene from Tyringham made a curious white, 

cat's eye. 

G. F. Kunz: Precious stones, Mineral Resources U. S. 1883-84, p. 728.

1892. Pyroxene.

J. D. Dana: Sys. Min., 6th ed., p. 1059.

1895. Salite. Tyringham (on the south side of the valley, a half mile 

above Clark's).

Large prisms of pale salite, coated, and their interspaces Jilled with palegreen actinolite, on which are stout, curious quartz crystals, which include
EMERSON.] MINERAL LEXICON. ' 117

actinolite. They (tie quartz crystals) have wavy and rounded faces, and 

terminate by two or three pyramids. 

D. Clark collection.

1895. Pyroxene. Tyringham (D. Clark farm).

Bowlders of Stockbridge limestone. The mass contained in great numbers doubly terminated crystals of white pyroxene uniformly 1 inch long, 

half an inch wide, and considerably flattened by the great development 

of the orthopinacoid. It has the forms ooPoo (100), ooP (110), -fP 

(111),-P (Hi).

D. Clark collection.

1895. Pyroxene. Lee (Upper Goose Pond, near Elwells Bocks).

Pale-green pyroxene in stout crystals with perfect basal parting, 1 

inch long, three-fourths inch across.

1895. Pyroxene. New Marlboro (road to Southfield, in deep digging 

in rusty rock by roadside).

Pre-Cambriau. Green crystals an inch square, much cracked and corroded. 

D. Clark collection.

1895. Pyroxene changing into hornblende. Tyringbam (foot of Long 

Mountain).

Pre-Cambrian. Coarse square prisms an inch across and 2 to 3 inches 

long, of pale-green pyroxene, project outwardly from the limestone, and 

green bladed actinolite grows from it so as to spoil the surfaces of the 

pyroxene.

D. Clark collection,

1895. Pyroxene passing into tremolite. Tyringham (a half mile 

southeast of D. Glark's).

Pre Cambrian. In the same way as above described the whitish green 

pyroxene prisms appear here corroded and separated into distinct cubical 

blocks, which are much displaced, and out from the whole surface of the 

prism grew groups of radiate sheaf-like masses of tremolite, with needles 

often bent. A secondary green pyroxene, having a broad OP (001) face 

with P (111) and a second prism, is also developed at this locality.

D. Clark collection.

1895. Pyroxene. Tyringham (Hop Brook gorge).

Pre-Cambriau. Deep emerald-green transparent prisms, with perfect 

basal parting and poor prismatic cleavage. Many twins, twinning parallel to ooPoo (100) and reaching 4 inches in length. Other crystals are 

blackish green and pale green. The following combinations occur:

oo P (110), Poo (101), OP (001).

oo P (110), P* (101), OP (001), Poo (101).

oo P (110), Fob (101), Poo (101), -f-P (111), P (111), 2 P (221), OP 

(001).

Minute, long, square prisms occur in greasy wernerite. Other crystals 

occur with the first combination above; stout crystals an inch broad and 

2 inches long, deep green, with dull etched surface.

D. Clark collection.

1895. Salite. Tyringham (Sodom, below Hop Brook gorge).

The finest salite prisms of dull white color and an inch across and 2 to 

4 inches long. The base occurs implanted in black, white, and pink quartz, 

distantly or thickly scattered. They show the perfect basal parting. 

Often the prisms have been dissolved and the etched fragments sometimes remain in the square cavities in the black quartz, and blades of 

white tremolite tapestry the walls as if they had been formed from
118 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

the dissolved pyroxene. The pyroxene had often been broken and receinented by quartz, so that the cavities had cross partitions of quartz 

like the tabulae of a rugose coral. These quartz masses, from which the 

pyroxene has disappeared, were called by the early geologists mortised 

rock and thought to be the work of- Indians. In the gorge itself occur 

stout columnar masses of crystals an inch across, which are as large as 

one's fist. The quartz is pseudornorph after albite. See Pis. II, III, p. 52. 

D. Clark collection.

1895. Salite. Otis Center.

Bowlder. Coarsely cleaving, with cleavage surfaces several inches 

across; pale-green to white color.

1895. Pyroxene. Becket (100 rods east of E. Alderman's).

In pre-Cambrian limestone in large masses of pale-green, massive, coarse 

pyroxene rock and in loose aggregates of stout eight-sided prisms with 

strong prismatic and basal cleavage.

1896. Augite. New Marlboro (Cleveland mine).

W. H. Hobbs describes and figures a light-green hornblende which is 

surrounded and intergrown by a colorless pyroxene ("augite"), the two 

being orientated. Science, Vol. XX, p, 516.

PYEEHOTITE.

1895. Pyrrhotite in crystals. New Marlboro (Hotchkiss and Cleveland mines).

Hotchkiss mine; often an inch long; tapering hexagonal prisms with 

basal planes. Massive at the Cleveland mine.

1896. Pyrrhotite. Becket (M. J. Alderman's place).

In large masses from pre-Cambrian limestone. ,

1897. Pyrrhotite. Dalton (limestone locality on brook south of clubhouse on Day Mountain). 

Collected by B. F. Newell.

QUAETZ.

1822. Granular quartz. Hinsdale.

It is said to occur in large friable masses, snow white and much resembling sugar. It may prove important in the manufacture of glass and 

stoneware.

P. Cleaveland: Min., Vol. I, .239. Refers to great bowlders of Cheshire 

quartzite. Cited 1825 by S. Robinson: Cat. Am. Min., p. 53.

1824. Quartz. Lenox. Lee. Hindsdale. Pittsfleld. Washington.

Flattened terminated prisms; in quarry at Lenox.

Granular or as sand; everywhere. Yellow and red; Pittsfield, a considerable rock composed almost entirely of small crystals. Chalcedony, yellowish hornstone, cacholong, and opal; Hinsdale. Buhrstone; Washington.

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII,p. 38. Cited 1825 

by S. Robinson: Cat. Am. Min., p. 55.

1824. Blue quartz, fetid quartz, hornstone. Lenox. Pittsfield.

Ferruginous quartz, massive and well crystallized, Lenox. Hornstone 

jasper, generally gray and blue, Pittsfield.

J. Porter: Miu. Loc., Am. Jour. Sci., Vol. VII, p. 252.

1824. Cacholong, hornstone, chalcedony. Hinsdale.

C. Dewey: Geol. western Mass., Am. Jour. Sci., Vol. VIII, p. 39.
EMEKSON.] MINERAL LEXICON. 119

1825. Cacholong.

Before cited.

S. Robinson: Cat. Am. Miu., p. 54.

1825. Yellow ferruginous quartz. Dalton.

Crystallized and amorphous. J. Porter. 

S. Robinson: Cat. Am. Miu., p. 47.

1825. Jasper, hornstone, agate, quartz crystals, ferruginous quartz.

Pittsfield. Dalton. New Marlboro.

Massive and crystallized. Very large agates in masses of hornstone and 

jaspery quartz and jasper; Pittsfield. Ferruginous quartz in yellow crystals; Dalton. 

Arenaceous quartz; New Marlboro.

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 43.

1825. Blue quartz. Windsor.

Of good color in amorphous masses. (J. Porter.) 

S. Robinson: Cat. Am. Min., p. 77. 

1841. Chalcedony. Tyringham.

E. Hitchcock: Final Rept., p. 186.

1841. Mammillary chalcedony. Tyringliam.

Nos. 2328, 2329 in catalogue of State collection.

(Quartz.)

E. Hitchcock: Final Rept., p. 819.

1854. Mammillary chalcedony. Tyringham.

Nos. 236, 237.

E. Hitchcock: Cat. Rocks of Mass., 6th Rept. Mass. Bd. Agri., Appendix, p. 54.

1876. Quartzite, iron flint. Hinsdale.

C. U. Shepard: Cat. Min. within 50 miles of Amherst, p. 7.

1890. Quartz. Hinsdale.

Large geode cavities, with fine slightly smoky crystals, doubly terminated with very short prisms associated with specular iron.

Coll. of E. B. Underbill, Hallock Mills, N. Y. Presented to Amherst 

College, 1888. 

1890. Quartz. Becket (east of Shaw Pond).

Blue chalcedony with drusy surfaces, in bowlders of pre-Cambrian gneiss.

1895. Amethyst. Becket (R. Alderman's).

In contact selvage of pre-Cambrian limestone with actinolite, etc.

1895. Quartz. Mouterey (Bear Mountain).

Pre-Cambrian. In pale smoke-gray crystals, with etched and rounded 

faces, associated with tine fibrous actinolite and graphite. 

D. Clark collection.

1895. Quartz. Tyringham (the Cobble).

In well-terminated crystals in a granite vein. 

D. Clark collection.

1895. Rose quartz. Otis (roadside near east side of Tyriughain). 

D. Clark collection.

1895. Yellow jasper. Tyringham.

In drift; with surface of blue chalcedony. Also a deep liver-red jasper 

brecciated with white, from bowlder in John Winthrop pasture. 

D. Clark collection.
120 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

1895. Chalcedony. Tyringham (D. Clark farm, one-fourth mile east 

of house).

Beautiful great masses of translucent chalcedony; flesh color to amber, 

with small botryoidal surface of bluish or whitish shade.

D. Clark collection.

1895. Jasper. Monterey (Marshall Bid well's land, near Lake Garfield).

Jasper of various shades of yellow, often colored black by manganese 

and coated by fine drusy quartz; also colored black by manganese and 

running into fine blue shades, often raised above the general surface in 

matted masses of finely interlaced threads, as if the quartz had coated 

rootlets. This is the best locality, but the same jasper is found all up and 

down the Tyringham Valley in the drift at Feruside, in Otis, in Becket, 

where a great mass was blasted in the roadside, and near the West Becket 

post-office. All these jaspers indicate faults.

D. Clark collection.

1895. Brown jasper-agate. Tyringham.

Beautiful botryoidal masses showing white and brown concentric rings 

from the truncation of the balls. 

D. Clark collection.

1895. Black quartz. Tyringham (the Cobble and at the foot of the 

Hop Brook gorge).

A black quartz vein, the mineral often beautifully iridescent from fissuring. 

D. Clark collection.

1895. Cellular quartz. Tyriiigham.

Bowlder. A quartz breccia with the pebbles dissolved out. A fault rock 

probably brought south from the South Dalton fault. 

D. Clark collection.

1895. Fetid quartz (necronite). Tyringham.

Bowlder.

D. Clark collection.

1895. Quartz crystals. Tyringham (Fernside).

Fine limpid crystals half an inch long.

1895. Greasy quartz. Lee.

From a bowlder on the old turnpike from Lee to South Lee, one-fourth 

mile south of the covered bridge. A fine greasy quartz, white and deep 

leek-green.

D. Clark collection.

1895. Quartz pseudomorph after albite and containing salite crystals which are often dissolved or replaced by treinolite. Tyringham (Sodom). 

In pre-Cambrian limestone; see page52 for figures and full description.

1895. Amethyst. Tyringham (near Upper Goose Pond). 

Of pale color.

1896. Chalcedony. Otis Center.

Bowlder. Very large masses of a white chalcedony, which in cavities is 

fine botryoidal, drusy, and of faint sky-blue color.

It includes angular fragments of a yellow jasper, showing that it is the 

filling in of a vein in which the yellow jasper had been a previous filling 

shattered by a later movement of the vein walls. Both contain fragments 

of the wernerite, which shows that they are fillings of fissures in the calcite bed on the Otis fault.
EMERSON.] MINERAL LEXICON. 121

1896. Jasper. Hinsdale.

In large masses on west slope of hill 1,720 feet high, 2£ miles north of 

station. .Also on Pern road north of Ashmere Lake, in yellow, red, and 

white colors. (Doubtless from Cheshire quartzite.)

Collected by B. F. Newell.

RUTILE.

1825. Red oxide of titanium. Pittsfield (southeast part; in green 

quartz). Dalton (in quartz). New Marlboro.

C. A. Lee: Miu. Loc., Am. Jour. Sci., Vol. IX, p. 42.

1832. Rutile (Peritoneous Erythrone-ore). Windsor.

The locality affording rutile in the greatest quantity in the United 

States is a very extensive ledge of chlorite slate at Windsor, Mass. The 

crystals of rutile are here thickly disseminated through narrow veins 

of feldspar traversing this rock, and also occur in seams in the rock itself.

C. U. Shepard: Treat. Min., Vol. II, Pt. I, p. 169.

1844. Rutile (Peritoneous Urythrone-ore). Windsor.

Fine crystals thickly disseminated through veins of feldspar intersecting 

chlorite slate. 

J. D. Dana: Sys. Min., 2d ed.; p. 421.

1852. Rutile. Windsor.

C. U. Sbepard: Treat. Min., p. 256.

1868. Rutile. Windsor.

J. D. Dana: Sys. Min., 5th ed., p. 161.

1876. Rutilite. Windsor.

C. U. Shepard: Cat. Min. within 50 miles of Amherst, p. 7.

1881. Rutile. Windsor.

In red-brown deeply striated prisms up to 1-J- inches long, closely resembling the Chester County, Pennsylvania, variety. In white albite.

1892. Rutile. Windsor.

J. D. Dana: Sys. Min., 6th ed., p. 235. 

1895. Rutile. Tyringham. Daltou (Cottsville quarry).

Bowlder in Stockbridge limestone. Dark red-brown striated needles.

SCOLECITE. 

1895. Scolecite. Tyringbam (Hop Brook gorge).

Radiated blades on orthoclase. In masses of radiated tufts and globules 

graduating upward into fine globes of 1 inch in diameter of finest fibrous 

character, also in thick masses so finely fibrous and altered to kaolin that 

it has a massive porcelaneons look and botryoidal surface, also a soft, 

drusy surface growth forming great masses of balls an inch across. It 

also occurs encrusting biotite and pyroxene, and in a later generation with' 

other zeolites. See p. 55.

D. Clark collection.

1895. Scolecite pseudomorph after wernerite. Tyringham (Hop 

Brook).

(See under wernerite.) 

D. Clark collection.
122 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS.

SEBPENTINE.

1823. Serpentine. Windsor (northwest part).

C. Dewey: Geol. western Mass., Am. Jour. Sci., Vol. VIII, p. 50.

1824. Serpentine. Windsor.

C. Dewey: H'st. Berkshire County, p. 191.

1824. Vert antique? Becket.

A magiiesian mineral found in a bed in gneiss on the river in Becket, 

colored green by serpentine. It may, as Dr. Emmons supposes, be a serpentine marble. It is a tough mineral and takes a fine polish. The quantity of serpentine is sometimes small and the color yellowish white.

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 58.

(This is the Coles Brook limestone with altered chondodrite.)

1825. Vert antique.

The above localities in Windsor and Becket cited. 

S. Robinson: Cat. Am. Min., p. 77.

1825. Serpentine. Daltoii (east part of town). 

Containing asbestos. 

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 43.

1841. Serpentine. Windsor (northeast and north west parts). Cheshire 

(south of M. House's, a little east of the four corners).

Windsor, northeast part; serpentine with chondrodite. Cheshire ; hard 

serpentine in gneiss. 

Catalogue of State collection. 

E. Hitchcock: Final Rept., pp. 616,877,878.

SPINEL.

1892. Spinel. Norfolk, Connecticut.

Spinel is absent in the pre-Cambrian limestones of the Sandisfield and 

Becket quadrangles, and first appears south of the border of the map in 

Norfolk in the same limestone.

STAUEOLITE.

1822. Staurolite. Pittsfield.

In small, light-brown crystals, either single or crossing each other at 

right angles.

It is associated with garnets and sulphuret of iron (Hall). 

T. Cleaveland: Treat. Min., Vol. II, p.776.

1823. Staurotide. Hinsdale. >

"In vast quantities in mica-schist." Am. Jour. Sci., Vol. VI, p. 219.

S. Robinson: Cat. Am. Min., p. 53. This is a citation from Hitchcock's 

Geology of the Connecticut, and refers to Hinsdale, New Hampshire. 

Hitchcock is giving the list of towns up the Connecticut and crosses the 

State line without indicating it.

1824. Staurolite. Sheffield.

In small area of mica-schist.

C. Dewey: Am. Jour. Sci., Vol. VIII, p. 7.

1885. Staurolite.

J. D. Dana: Am. Jour. Sci., 3d ed., Vol. XXIX, p. 214.
EMERSON.] MINERAL LEXICON. * 123

STILBITE. 

1895. Sphserostilbite. Tyringham (Hop Brook).

Pro-Cambrian. In balls with faceted faces, radiated within with pearly 

luster. Fine groups coating biotite; also in sheaves and in. segments of 

wheels. Onebeautifulcylinclricalmass, 7incheshigh, 4£ inches in diameter, 

covered with the warty protuberances made of the fine spheres, was sent to 

the exposition at Chicago. One mass more than a foot across was found. 

There is also a second growth of small, single crystals of stilbite. It occurs 

also in separate projecting and interlaced thick blades oo P 66 (010), oo P 

do (100), OP (001). Color, opaque-white, often smoky exteriorly. Other 

crystals appear with tapering ends from the development of P (111). 

Other specimens are small, limpid, single crystals oo P do (100), oo P do 

(010), OP (001).

The zeolites were found in a rotten vein in the coarse pyroxene rock 

with big crystals of dark brownish black biotite changed to jeft'erisite; 

well-formed crystals 1^ inches to 5 inches across, some often fused together 

by sphserostilbite and deeply warped.

D. Clark collection.

SULPHUE.

1824. Sulphur. Tyringham. 

In mica-slate. 

C. Dewey: Geol. western Mass., Am. Jour. Sci., Vol. VIII, p. 54.

1824. Sulphur. Hinsdale.

In cavities of a mica-slate rock consisting chiefly of quartz. It is a 

brown powder, from its mixture probably with oxide of iron. 

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 33.

1825. Sulphur. Localities in Tyringhain and Hinsdale cited above.

S. Robinson: Cat. Am. Min., pp. 54, 73.

I have not found sulphur in the cavities of the Hinsdale gneisses, which 

are, however, often filled with a yellow pulverulent limonite.

TALC.

1823. Steatite (potstone). Windsor.

Very fine; formerly wrought into inkstands, which are still made by 

Shakers. 

C. Dewey: Geol. western Mass., Am. Jour. Sci., Vol. VIII, p. 51.

1824. Talc. Windsor.

C. Dewey: Hist. Berkshire County, p. 191.

1824. Steatite. Windsor.

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 51.

1825. Steatite.

Cited above. Also talc. (H. M. Wells.) 

S. Robinson: Cat. Am. Min., p. 77.

1825. Talc. Pittsfield.

Of different colors.

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 43.

1841. Steatite. Hinsdale.

E. Hitchcock: Final. Rept., p. 156.

1841. Steatite. Hinsdale.

In gneiss.

E. Hitchcock: Final Rept., p. 610.
124 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

1892. Talc. Hinsdale.

The great beds of talc connected with the Hinsdale limestone are 

described on pages 28-32. The largest beds are at the q uarry near Wakonah 

Falls, the stratum being 30 feet thick, where the brook from Ashmere 

reservoir crosses River Bend Farm below the mill pond.

TITANITE. 

1824. Red oxide of titanium. Pittsfield.

In small prisms in quartz associated with dolomite; rare. 

C. Dewey: Geol. Berkshire, Am. Jour. Sci., Vol. VIII, p. 58.

1841. Sphene. Lee (east part of town). Tyringhain.

Lee; in aiigitic gneiss: finest in New England; No. 1091, Gat. State 

Coll., p. 637. In talcose limestone, No. 1981, Cat. State Coll., p. 810. 

Tyringham; with hornblende, No. 2301, Cat. State Coll., p. 818. 

E. Hitchcock: Final Rept. Geol. of Mass.

1844. Sphene (Eutilus oUiquus}. Lee (eastern part).

Very good specimens in gneiss.

J. D. Dana: Sys. Min., 2d ed., p. 422.

1854. Sphene. Becket.

In talcose limestone (probably Coles Brook bed).

E. Hitchcock: No. 193, Cat. Mass. Coll., Agri. Rept., p. 35.

1858. Sphene. Tyringham.

With hornblende; No. 210.

E, Hitchcock: Cat. Mass. Rocks in 6th Ann. Rept. Mass. Bd. Agri.

1868. Sphene.

. J. D. Dana: Sys. Min., 5th ed., p. 386.

1872. Sphene.

J. D. Dana: Sys. Min., 6th ed., p. 715.

E. Hitchcock: Final Rept. Geol. of Mass.

1895. Titanite. Saudisfield. Becket. Coles Brook.

Sandisfield; in drift on Birch Hill, with hornblende and wernerite.

Becket; 100 rods east of R. Alderman's house.

Crystals a half inch long.

Coles Brook; in Hinsdale limestone.

1895. Titanite. Tyringham (Sodom, Hop Brook gorge).

In pre-Cambrian limestone. Beautiful flat transparent chestnut-brown 

crystals, often an inch long. Some are rich red-brown at one end and grade 

to clove-brown or dusty-white at the other. There are also most beautiful 

limpid hyacinth-red bladed crystals in calcite. In Sodom chestnut-brown 

crystals occur in pink calcite with radiating black hornblende. They 

show the faces OP (001), P (111), ooPoo (100), ooP (110), and multipl« 

twinning according to the third law (Dana) approximately parallel to 221.

D. Clark collection.

1895. Titanite. New Marlboro (road to Soutb field).

Deep cutting in rusty rock by roadside. Pre-Cambrian. Large palebrown wedge-shaped crystals. 

D. Clark collection.

1895. Titanite. East Lee (east of the Gousset road).

Bowlder of pre-Cambrian Hinsdale limestone.

The crystals are half an inch long and of pale Isabella yellow. Forms: 

OP (001), ooPoo (100), ooP (110), P (111). 

D. Clark collection.
EMERSON.] MINERAL LEXICON. 125

1895. Titanite. Becket (near West Becket .post-office).

A large mass was blasted out in improving the road. The mineral occurs

- in a white, granular feldspar rock (pre-Cambriau), with green actinolite, 

and is probably from an altered form of the Hinsdale limestone. It is in 

very abundant crystals of rich chestnut color, often an inch long, and 

shows the forms OP (001), P (111), oo P (110). 

D. Clark collection.

1895. Titanite. Otis (Hop Brook gorge).

From the upper bed of pre-Cainbrian limestone. Flat-bladed chestnutbrown crystals an inch long. 

D. Clark collection.

TOTJBMALINE.

1821. Schorl. Dalton. Pittsfield (southeast part of the town).

In mica-slate. ' 

C. A. Lee: Min. Loc., Am. Jour. Sci., Vol. IX, p. 42.

1822. Yellow tourmaline. Dalton (near the Housatonic).

In groups of straw-yellow crystals from an inch to 2 inches long, sometimes with terminations in granular limestone (M'Euen).

P. Cleaveland: Min., p. 321.

This interesting "occurrence I have not been able to verify. It may be 

tremolite in the Stockbridge limestone, but from the great abundance of 

minute tourmaline in the subjacent Cheshire quartzite the occurrence of 

tourmaline in the limestone is not improbable.

1824. Black tourmaline. Washington.

J. Porter: Min. Loc., Am. Jour. Sci., Vol. VII, p. 252. 

I have not found this mineral in Washington.

1825. Yellow tourmaline. Dalton (near the Housatouic).

In groups of straw-colored crystals in granular limestone. 

S. Eobiuson: Cat. Am. Min., p. 46.

1895. Tourmaline. Sandisfield (in field near Mr. George Blake's 

house).

Black crystals 1 inch across and 3 to 5 inches long, in a small pegmatite 

vein, much jointed, faulted, and recemented into beautiful series of echeloned disks.

1895. Tourmaline. Tyringham (the Cobble).

In well-terminated black crystals in a granite dike. 

D. Clark collection.

1895. Tourmaline. Sandisfield (near town hall).

Black crystals 1$ inches across, much jointed, and recemented with 

quartz. 

D. Clark collection. ,

WERNERITE. 

1841. Scapolite. Tyringham. Lee.

Tyringham; crystallized hornblende and scapolite; No. 2300, State collection.

 Lee; augite with scapolite; No. 1092, State collection. 

E. Hitchcock: Final Kept. Geol. of Mass., p. 818.
126 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. lBULLx.l59.

1844. Scapolite. (Scapolus pyramidalis.) Tyringham. 

.T.D.Dana: Sys. Min., 2d ed., p.539.

1858. Scapolite. Tyringham.

With hornblende.

E. Hitchcock: No. 218, Cat. Rocks of Mass., 6th Ann. Rept. Mass. Bd. Agri.

1868. Scapolite.

J. D. Daua: Sys. Min., 5th ed., p. 770.

1892. Scapolite.

Idem, 6th ed., p. 1059.

1895. Wernerite. Tyringham (Hop Brook gorge, Sodom).

Pre-Cambrian. Pure white prisms 2 inches long and 1 inch square. 

Other crystals in almost acicular square prisms; crystals generally bent 

or broken by later growth of hornblende.

D. Clark .collection.

1895. Wernerite. Lee (Upper Goose Pond, near Elwells Eocks).

Peculiar forms; deep topaz to flesh-colored; glassy and highly lustrous 

on crystal faces; transparent, and a true gem form. Some crystals broken. 

The crystals are black at base and change up through brown and wineyellow to nearly colorless. Inset crystals raised from the polished faces. 

The oc P oo (101) cleavage is perfect; crystals are half an inch wide and 

1 inch long, with the form oo P oo (101), P (111).

Masses 2 inches square show deep flesh-color; more fibrous cleavage, like 

ordinary scapolite; growing paler by alteration. Blades of deep-green 

actinolite and pyroxene prisms are grown through the mass.

Also large masses of coarse granular texture composed of imperfect stout 

crystals 1 inch across, bluish gray shading to white at border, and very 

fresh, greasy luster, with biotite.

D. Clark collection.

1895. Wernerite changing into scolecite. Tyringham (Hop Brook 

gorge).

Large imperfect square prisms, with greasy bluish luster, and masses of 

a colorless wernerite granular rock, full of small phlogopites and actinolite blades, are changed to a mass of radiated fine fibrous balls of scolecite, 

opaque white, at the surface forming delicate botryoidal surfaces of the 

fine free needles. In cross sections the balls are concentrically banded, 

the lower half opaque-white, the upper translucent. This wernerite is 

found in masses of tons in size along the brook gorge, white and pale 

gray, with crystals growing from the surface. Other crystals are small 

square prisms one-half inch long, one-fourth inch wide, often bent; snowwhite, with satiny luster, apparently changed to scolecite in needles parallel to OP (001). Other specimens are also coated with the radiated balls 

of scolecite as above. One piece bristles with white needles of wernerite 

one-half millimeter across, many of which are deep square hollows, 

leaving only shells, and many are inclosed in deep-green pyroxene and 

remain hollow.

D. Clark collection.

1895. Wernerite. Tyringham (Hop Brook).

A large impure crystal, full of calcite and phlogopite, was examined in 

thin section under the microscope. The crystal is full of minute, long, 

square prisms, whose cleavage, high relief, and oblique extinction show 

them to be white pyroxene. The wemerite is brown, shaded in irregular 

patches, which are white by reflected light. This is caused by the fibrous
EMERSON.] MINERAL LEXICON. 127

decompoaition product common in wernerite, which is optically positive 

and has very weak double refraction (V = .008), agreeing exactly with 

scolecite. A twinning suture runs parallel with OP (001), and the optical 

axis makes an angle of 16° with this on either side.

1895. Wernerite. Sandisfield (Beech Plain).

In drift, with hornblende and titanite.' 

1895. Wernerite. Otis (Otis Center).

The coarse limestone at Otis Center contains wernerite in groups of 

stout, white, interlaced crystals and purple glassy masses. It occurs in the 

brook bed near the mill and just west of the village street.

ZOISITE. 

1841. Zoisite. Hinsdale.

In, mica-schist. f 

E. Hitchcock: Final Kept., 606.

(I have never seen zoisite from Hinsdale. It may be the same mineral 

cited herein as h'brolite.)

1844. Zoisite. (Carbunculus rliomboideus.} Hinsdale. Windsor. 

J.D. Dana: Sys.Min., 2d ed.,p. 300.

1868. Zoisite.

Idem, 5th ed., p. 292.

1892. Zoisite.

Idem, 6th ed., p. 514.
BIBLIOGRAPHY. '

1734. WINTHROP (John). Selections from an ancient catalogue of 

objects of natural history found in New England more than a 

hundred years ago, by John Winthrop, F. E. S., from the Journal Book of the Royal Society, Vol. XV, p. 451. (Manuscript.) 

Am. Jour. Sci., Vol. XLVII, p. 282, 1824.

1809. MACLUEE (W.). Observations on the geology of the United 

States, with geological map. Trans. Am. Philos. Soc., Vol. VI, 

pp. 411, 428.

1814. MEADE (W.). Mineralogical notice concerning elastic marble 

from Massachusetts. A. Brace, Am. Min. Jour., Vol. I, pp. 93, 

267.

On taking up one of these slabs it was found to be so completely elastic 

that the writer feared it would fall in pieces before he could replace it.

1816. CLEAVELAND (Parker). Elementary treatise on mineralogy and 

geology, with colored geological map of the United States j 668 

pages.

The map was taken from Mac lure. Berkshire County is colored as 

"Primitive."

1818. EATON (Amos). An index to the geology of the northern States, 

with a transverse section from the Catskill Mountains to the 

Atlantic, prepared for the geological classes at Williams College, Northampton, Belchertown, Leicester, and Worcester 

(Massachusetts).

The section gives, although crudely, the Hinsdale anticline, hut makes 

its core granite instead of gneiss, and identical with the much later granite of Chesterfield. On this granite rest the "granular limestone" and 

quartz. This is the Hinsdale limestone, and it is clearly separated from 

the newer "metalliferous limestone" to the west, the latter being the 

Stockbridge limestone (p. 84).

Next above this is the gneiss, which "sinks laterally under the micaschist to the west, and probably does not rise again until it reaches the 

continent of Asia." Above this is the mica-slate, "the calcareous and 

granular quartz," the "soapstone rocks," including the hydromica-schists, 

as well as the steatite and serpentine, and lastly the "syenite." By this 

is meant the Chester and Hawley amphibolites, and he notes the spotted 

or "porphyritic" varieties in Hawley. This bed is said to cap the series 

east of Dalton, and "therefore all the tract is 'Primitive.'"

1818. MACLURE (W.). Observations on the geology of tlie United

States, with map. Trans. Am. Philos. Soc., n. s., Vol. I, p. 1. 

1820. EATON (Amos). An index [etc.]; 2d edition.

"Written over anew." 

1820. Localities of minerals, from the minutes of the Troy

Lyceum. Am. Jour. Sci., Vol. II, p. 238. 

128
EMERSON.] BIBLIOGRAPHY. 129

182}.. DEWEY (0.). Fetid dolomite found in Lee; found by analysis to 

be magnesia. Am. Jour. Sci., Vol. Ill, p. 239.

1822. CLEAVELAND (Parker). An elementary treatise on mineralogy 

and geology. Second edition, 2 vols. With copy of W. Maclure's geological map, from work cited above, 1818.

1822. DEWEY (0.). Prismatic mica (Hinsdale). Am. Jour. Sci., Vol. V, 

p. 399.

1823. PORTER (Jacob). Localities of minerals. Am. Jour. Sci., Vol. 

VI, p. 246.

1823-6. Boston Journal of Philosophy and the Arts. J. W. Webster, 

editor. 3 vols.

Catalogues of minerals from several localities.

1824. A history of the.county of Berkshire, Mass. By gentlemen of 

the county, clergymen, and laymen. Colored geological map.

Geology by Prof. Chester Dewey. The central gneiss mass, with soapstone and serpentine, is mentioned. The quartzite and the limestone are 

said to extend south in two bands; the western, from Adams to Cheshire, is 

the Stookbridge limestone; that from Windsor to New Marlboro is preCambrian.

1824. HALL (F.). Catalogue of minerals.

1824. PORTER (Jacob). Localities of minerals. Lenox, Pittsfleld, 

Washington. Am. Jour. Sci., Vol. VII, p. 252.

1824. DEWEY (Chester). A sketch of the geology and mineralogy of 

the western part of Massachusetts, and a small part of adjoining States. Am. Jour. Sci., Vol. VIII, pp. 1-60. Geological 

map.

The first connected account of the geology of Berkshire County. All 

the upland country mapped in this study is assigned to mica-slate except 

a band of gneiss along the Peru line and a broad band of primitive limestone which runs down across Hinsdale and Washington and is given the 

same color as the valley limestone. The quartzite is the only other rock 

distinguished upon the map.

1824. . Additional remarks on foregoing. Arn. Jour. Sci., Vol., 

Ill p. 240.

1825. LEE (Charles A.). Notice of minerals in Pittsfield and Dalton. 

Am. Jour. Sci., Vol. IX, pp. 42, 43.

1825. KOBINSON (Samuel). A catalogue of American minerals, with 

their localities. Boston.

Quotes minerals from Becket, Dalton, Hinsdale, Lee, Lenox, New Marlboro, Pittsfield, and Windsor.

1830. EATON (Amos). Geological text-book. Albany.

Southeastern Berkshire is mapped as follows: limestone from the west 

up to the Hoiisatonic; quartzite east of this to Franklin and Hampshire 

counties; in the southeastern corner is primitive, interrupted by a baud 

of limestone entering from Litchfield County. 

Bull. 159 9
130 GEOLOGY OP EASTERN BERKSHIRE COUNTY, MASS. [BULL. 159.

1830. A history of the county of Berkshire, Massachusetts, in ,two 

parts5 the first being a general view of the whole county; the 

second an account of the several towns, by gentlemen of the 

county, clergymen, and laymen. Geographical and geological 

map.

Geological part by Prof. Chester Dewey.

1832. HITCHCOCK (B.). Eeport on the geology of Massachusetts, examined under the direction of the government of that State during 

the years 1830 and 1831 by Edward Hitchcock, professor of 

chemistry and natural history in Amherst College. Part I. 

The economical geology of the State, with a geological map. 

Am. Jour. Sci., Vol. XXII, p. 1.

1832. SHEPARD (0. U.). Treatise on mineralogy. 2vols. Few Haven.

1835. HITCHCOCK (E.). Second edition of above report on geology of 

Massachusetts, 1832.

1838. Eeport on the reexamination of the economical geology of 

Massachusetts.

Notice of the limonite.

1841. Final report on the geology of Massachusetts. 4°. 831 

pp., plates and map.

1842. PERCIVAI, (J. G.). Eeport on the geology of the State of Connecticut, with geological map. 495 pp. 8°. New Haven. 

Formation L (limestone) K3 (gneiss) are extended into Massachusetts.

1842. EMMONS (E.). Geology of New York, 2d district. 4°.

The discussion of the Taconic system extends into this region, under 

 " Granular quartz," p. 158.

1842. MATHER (W. W.). The geology of New York, 1st district.

All the limestones of western Massachusetts are said to be altered Lower 

Silurian, pp. 464,476,542.

1844. DANA (J. D.). System of mineralogy. 2d edition.

1844. HITCHCOCK (E.). Geological map of Massachusetts on the topographical map by E. Borden. Explanation of the above jnap, 

separate pamphlet. 8°. 22 pp. Boston.

1845. LYELL (C.). Travels in North America.

" The opinion of Professor Hitchcock and H. D. Rogers that the Taconic 

Range is altered Silurian appears to me highly probable." P. 195.

1852. SHEPARD (C. TJ.). A treatise on mineralogy. 3d edition. New 

Haven.

1853. MARCOU (J.). Geological map of the United States, with explanatory text. Boston.

See Bull. U. S. Geol. Survey No. 127.

1853. HITCHCOCK (E.). Outlines of the geology of the globe and of the 

United States in particular, with map. 

Area made hypozoic and metamorphic.
EUEBSON.] BIBLIOGRAPHY. 131

1854. HUNT (T. S.). On the crystalline limestones of North America. 

Am. Jour. Sci., 2d Ser., Vol. XVIII, p. 195.

All the limestones of western Massachusetts are Lower Silurian; the 

Archean limestones considered to be only more metamorphosed portions.

1855. MARCOU (J.). ITeber die Geologie der Vereinigten Staaten, mit 

Karte.

Makes the whole area granite ami metamorphic rock.

1855. EMMONS (E.). American geology.

Gives Greylock section of "Taconic rock" and explains the iroi: breccia as igneous.

1858. WALLING- (H. F.). Map of the county of Berkshire, based upon 

the trigonometric survey of the State. The details from actual 

surveys under the direction of Henry F. Walling.

1858. HITCHCOCK (E.). Geological map of Berkshire County. 

On the above topographical map.

1859. Agricultural museum catalogue of collection of rocks, 

minerals, and fossils in the State cabinet, obtained during the 

geological surveys of the State by Dr. Edward Hitchcock, with 

later additions. Appendix 6th Ann. Eept. of Board of Agriculture. Boston: State printer.

Collection in State capitol many years, then i'u Agricultural College, 

Amherst; thrown in confusion by a fire and not rearranged. Duplicate 

collection in Amherst College.

1866. HALL (J.) and GAGAN (W. E.). Geological map of Canada and 

the adjacent region, 1866.

The Stockbridge limestone is made Levis's 5a, in Quebec group, and the 

Hoosac schists are Sillery (6); all the rest Lauzon 56.

1868. DANA (J. D.). System of mineralogy. 5th edition.

1868. PERRY (J. B.). Life of E. Emmoiis. Proc. Boston Soc. Nat.

Hist, Vol. XII, p. 214. 

1871. HITCHCOCK (C. H.). Geological description of Massachusetts,

with geological map. Walling's Atlas of Massachusetts, p. 17.

Eozoic are "the gneissic rocks of the Hoosac Mountain Range, which 

have anticlinal structure." The quartz rock is the lower Potsdam of 

Billings. The Stockbridge limestone is Levis group of Canada. The 

Berkshire schist is " Lauzon " of Canada, and all those parts of the Que- 

- bee group above the Chazy are Sillery. The ." Talcose schist" (Hoosac 

and Rowe schists) are also Quebec. The Middlefield and Rowe serpen- 

, tines (that is, in effect, the Chester series) are the equivalent of the limestones in the schists of the Taconic Range. The map, by the inexcusable 

blundering of the colorist, is wholly worthless, and was repudiated by its 

author at the Boston meeting of the American Association for the Advancement of Science.

1871. CREDNER (H.). Die Geoguosie und der Mineralreichthum des 

Alleghany-Systems. Petermann's Mittheilungen, 1871, p. 41.

Makes the Berkshire Valley Huronian, the highlands Laurentiau.

1872. DANA (J. D.). Green Mountain geology. Am. Jour. Sci.,3d series, 

Vol. Ill, pp. 179, 250. 

On the quartzite.
132 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [BOLL. 159.

1872. DANA (J. D.). On the quarteite, limestone, and associated rocks 

of the vicinity of Great Barringtou, Berkshire County, Mass. 

Am. Jour. Sci., 2d series, Vol. IV, pp. 362, 450.

1873. Same, Vol. V, pp. 47, 84; Vol. VI, p. 257. 

1873. HITCHCOCK (0. H.) and BLAKE (W. P.). Geological map of the 

United States.

The hill country on the east is assigned to the Eozoic; the western valley to the Silurian.

18Y5. BRADLEY (F. H.). A geological chart of the United States.

The whole of Berkshire County is made Lower Silurian.

1876. SHEPARD (0. U.). Catalogue of minerals found within 75 miles 

of Amherst College. Privately printed May 20, 1876.

The greater number are found within 50 miles of this center.

1876. CROSBY (W. O.). Kepbrt on the geological map of Massachusetts, 

prepared for the Centennial Exposition at Philadelphia. Boston. 52 pp.

Noticed, probably by J. D. Dana, in Am. Jour. Sci., 3d series, Vol. XII, 

p. 459, where the statement that the Berkshire limestones and associated 

rocks are older than the Primordial is criticised and the Lower Silurian 

fossils found in Vermont are adduced.

1877. DANA (J. D.). On the relations of the geology of Vermont to that 

of Berkshire. Am. Jour. Sci., Vol. XIV, pp. 37,132,202,257.

1877. HITCHCOCK (C. H.). Geology of New Hampshire. 3 vols. Atlas 

in folio.

Vol. II, p. 8, PI. I, assigns the valley to the Silurian and Cambrian; Bear 

Mountain and the area south across Monterey, New Marlboro, and Norfolk to the Laureutian; and the broad area of the Cambrian gneisses 

to the east of these subdivisions to the "Atlantic" a subdivision of the 

Archean between the Laurentian and the Huronian.

1879. Macfarlane's railroad guide.

This gives Professor Hitchcock's views as to the age of the rocks in the 

area along the Honsatonic and Boston and Albany railroads. The Hinsdale pre-Cambrian is called Green Mountain gneiss; the hydromica-schist 

of Middlefield, Huronian.

1880. DANA (J. D.). Note on the age of the Green Mountains. Am. 

Jour. Sci., Vol. XIX, p. 191.

Only general considerations on this special region.

1881. HITCHCOCK (C. H.). Geological map of the United States and 

Territories. Julius Bien. Scale, 20 miles to an inch.

The gneisses are assigned to: "Gneisses of the Atlantic Slope, including 

Montalban/'and "Metamorphic Paleozoic;" the valley rocks, to Lower or 

Cambro-Silurian (Lorraine to Calciferous).

1882. DANA (J.D.). Geological age of the Taconic system. Jour. Geol. 

Soc., Vol. XXXVIII, p. 397.

Refutation of Hunt's idea of the pre-Cambrian age of the Taconic. The 

map gives the slates and limestones, leaves the highlands nnoolored, and 

writes over Bear Mountain, "Here some Archaean?"
EMERSON.] BIBLIOGRAPHY. 'JJ3

1883-1885. KUNZ (George F.). Precious stones; from Mineral Resourceb 

of the United States, U. S. Geol. Survey.

1884. NEWBERRY (J. S.). Notes on building stones used in New York. 

Tenth Census, Vol. X, pp. 318-324.

Lee marble, uniform, not brilliant white, coarser than Vermont, finer 

than New York marbles. Strong and durable, has little iron, and becomes 

somewhat brown on exposure. This is thought by some to be an excellence. Not weakened by the change.

1884. McGEE (W J). Map of the United States, exhibiting the present status of knowledge relating to the final distribution of 

geologic groups. (Preliminary compilation.) Compiled by W 

J McGee, 1884. Fifth 'Ann. Rept. U. S. Geol. Survey, PI. II. 

All the region given as Azoic-Archean.

1884. HITCHCOCK (C. H.). Geological map of the United States, in 

The National Atlas. Grey, Philadelphia.

1884. DANA (J. D.). On the decay of quartzite and the formation of 

sand, kaolin, and crystalline quartz. Am. Jour. Sci., Vol. 

XXVIII, p. 448.

1. Sand from quartzite. 2. Feldspathic quartzite the source of the 

kaolin. 3. Pseudobreccia from quartzite and in some of this pseudobreccia crystallized quartz.

1884. HAWES (G. W.), KELLEY (C.), MERRILL (G. P.), and SHALER 

(N. S.). Report on the building stones of the United States. 

Tenth Census, Vol. X.

Muscovite-biotite-gneiss of the Chester Granite Company, called 

Archean, p. 54.

1884. WHITNEY (J. D.) and WADSWORTH (M. E.). The Azoic system, 

Vermont and western Massachusetts. Bull. Mus. Comp. Zool., 

Vol. VI, p. 440.

So far as relates to our area, the section is almost wholly devoted to an 

accurate and detailed exposition of T. Sterry Hunt's views on the Taconic 

system and its remarkable metamorphoses. It is thus wholly given to a 

discussion of post-Azoic rocks and rocks it recognizes as such, and'does 

not mention any of the rocks or areas of pre-Cambrian age in this territory.

1885. MERRILL (George P.). The collection of building and ornamental stones in the United States National Museum. A handbook and catalogue. Rept. Smith. Inst., 1885-86, Part II, 

pp. 277-618, Pis. I-IX.

1885. DANA (J. D.). Decay of quartzyte: Pseudo-breccia. Am. Jour. 

Sci., Vol. XXIX, p. 57.

Explains the breccias by the wedging action of crystallizing iron compounds.

1885. (1883-84.) HUNT (T. S.). The Taconic question in geology. The 

"Taconiari" is a late pre-Cambrian formation. Traus. Can. 

Roy. Soc., Vol. I, Pt. 4, p. 227; Vol. II, p. 125.

1885. DANA (J. D.). On Taconic rocks and stratigraphy, with a geological map of the Tacouic region. Am. Jour. Sci., Vol. XXIX, 

pp. 205, 437.
1J4 GEOLOGY OF EASTERN BERKSHIRE COUNTY, MASS. [Buu,l59.

1886. Topographical map of the State of Massachusetts. Executed by 

the United States Geological Survey, at the joint expense of 

the State and the Survey.

Scale 1: 62,500; 20-foot contours in brown; water in blue; roads in black.

1887. DANA (J. D.). On Taconic rocks and stratigraphy, with a geological map of the Taconic region. Am. Jour. Sci., Vol. 

XXXIII, p. 270.

Also published separately, with 1885 part.

1888. Geology of Berkshire County. Child's Berkshire County Gazetteer, pp. 24-26. 

Inadequate and worthless.

1888. WALCOTT (C. D.). The Taconic system of Emmoris, with map 

covering western border of the area. Am. Jour. Sci., Yol. 

XXXV, pp. 229, 307, 394.

1889. MERRILL (George P.). Handbook and catalogue of building 

and ornamental stones in the United States National Museum. 

Eept. Smith. lust., 1885-86, p. 277, Pis. I-IX.

1890. DANA (J. D.). Archaean axes of eastern North America. Am. 

Jour. Sci., Vol. XXXIX, p. 378.

1890. . Archaean limestone and other rocks in Norfolk, Connecticut. Am. Jour. Sci., Vol. XXXIX, p. 321.

R. H. Cornish writes of a limestone ledge with spinel and chondrodite 

on land of Mr. Ralph Cressey, near a spring southeast of his house.

1890. CROSBY(W.O.). Macfarlane's geological railway guide, 2d edition.

Gives character of rooks along Boston and Albany Railroad.

1890. EMERSON (B. K.). Porphyritic and gneissoid granites in Massachusetts. Bull. Geol. Soc. Am., Vol. I, p. 559.

Describes briefly the Archeau areas and their bordering conglomerate- 

. gneisses. The Hinsdale area is taken as type.

1891. WALCOTT (C.D.). Correlation papers: Cambrian. Bull. U. S. 

Geol. Survey, No. 81.

1891. MERRILL (G. P.). Stones for building and decoration. New 

York. John Wiley's Sons.

This adds nothing concerning building stones of Massachusetts to the 

handbook of the United States National Museum, 1885.

1892. HOBBS (William H.). Intergrowths of hornblende with augite 

in crystalline rocks. Science, Vol. XX, p. 354.

Augite surrounding hornblende, from the Cleveland mine.

1892. . Notes on some pseudomorphs from the Taconic region. 

Am. Geologist, Vol. X, p. 47.

Pseudomorphs of fibrolite and mica after feldspar.

1893. McGEE (W J). Reconnaissance map of the United States, showing the distribution of the geologic system so far as known.

Compiled from data in possession of the Geological Survey. Berkshire 

County, uncolored.
EMBHSON.] BIBLIOGRAPHY. 135

1894. McGBE (W J). Preliminary geologic map of New York, exhibiting the structure of the State so far as known.

Prepared by W J McGee under the direction of James Hall. A rounded 

area wholly southwest of the true pre-Cambriau of Bear Mountain is 

assigned to Laurentiau granite, including unclassified crystallines. The 

rest assigned to (Gg) Georgia formation, and (Strrn) Metamorphic, Trenton, 

and Calciferous limestone. *

1894. PUMPELLY (Raphael), WOLFF (J. E.), and DALE (T. Kelson). 

Geology of the Green Mountains in Massachusetts. Mon. 

U. S. Geol. Survey, Vol. XXIII. 

Notice in Am. Jour. Sci., 1896, p. 146.

1895. DANA (J. D.). Manual of geology, 4th edition.

1895. SHALEE (N. S.). The geology of the road-building stones of

Massachusetts. Sixteenth Ann. Eept. U. S. Geol. Survey, Vol.

II, p. 277.

Notice Am. Jour. Sci., 4th series, Vol. 1,1896, p. 489.

INDEX.

Page.

Actinolite-limestone, occurrence and character of.........'...................... 32

Amphibolite, occurrence of................. 59,69

figure showing dike of................. 75

Analyses,limestone.................. 32,69,85,87

nodules from gneiss.................... 68

water from artesian well at Dalton..... 91

white dolomite......................... 99

Arno & Co., assay made by................. 64

Artesian wells on Dalton fault............. 90-92

Assay of ore from Cleveland mine ......... 64

Barker, Charles T.,mentioned.............. 53

Bear Mountain, note on name of ........... 13

Bear Mountain anticline, description of.... 58-60

Becket, analysis of limestone from......... 69

high terraces in ........................ 97

Becket gneiss, occurrence of ...... 55,60,61-62,63

sections showing occurrence of .. 36,41,61,65 

Berkshire County, topography of .......... 14-17

Berkshire schist, description of ............ 88

Bibliography............................. 128-135

Biotite-ainphibolite, occurrence of.......... 75

Biotite-gneiss, occurrence and character of. 24,68 

Biotite-microeline-gneiss, occurrence and

characterof........................ 23-24

Blandford, analyses of limestone from...... 69

Blue-quartz gneiss, occurrence and character of......................... 27, 37-39, 72

Buhrstoues, occurrence of.................. 100

Campbell Falls section, description of...... 66-67

figure showing ......................... 66

Center Pond, description of limestone bed

near................................ 43

Cheshire quartzite, occurrence and character of................................ 78-79

Choudrodite-limestone, analysis of......... 32

occurrence and characterof............ 31-32

Clark, Daniel, aid by.................. 46, 52, 53-54

Cleveland area, description of.............. 03-65

Cleveland mine, section at.................. 64

Coal, prospects of finding................... 102

Coles Brook, section of pro-Cambrian rocks at 41 

Coles Brook anticline, unconformity at.-.... 70-71

Coles Brook limestone, occurrence and description of......................... 41-43

section showing........................ 42

Coltsville mica-schist bed, description of... 82 

Conglomerate-gneiss, description of........ 71-75

Connecticut River, watershed between Housatonic River and .................. 14-15

Cyanito, figure showing section of......... 26

Page. 

Dale, T. N., reference to .................... 13,19

suggestion by.......................... 85

Dalton, analysis of water from artesian well

at.................................. 91

record of well borings in................ 90,91

Dalton anticline, description of............ 39-40

figure showing......................... 40

Dalton bed, description of.................. 82

Dalton fault, artesian wells upon .......... 90-92

description of.......................... 89-92

Dalton katues, description of............... 97

Dana, J. D., cited on Hinsdale limestone... 27,47 

cited on paeudobreccia ................. 80

cited on Taconio rocks........'......... 51,65

Dewey, C., cited on kaolin.................. 80

cited on quartzite breccia.............. 80

Dolomite, analysis of white................ 99

tests of strength of..................... 99

Dry Hill, mica-schist of.................... 82

East Lee anticline, description of.......... 45

East Lee limestone, occurrence of ... '...... 50-51

East Lee Valley, deflected glacial drainage

in................................1. 98

high sands at entrance of .............. 98

Epidote-gneiss, occurrence and description

of.................................: 24-27

Erosion, effect upon topography of......... 18

Farming-ton River Valley, bowlders in..... 57

Faults on Ferncliff Ridge, description of... 88-89 

Ferncliff Ridge, geology of.................. 85-89

lithology of............................ 80

structure of............................ 86

Fitts, F. H.. analysis made by ............. 32

Flagstones, extent and character of........ 100

Foxdeu anticline, description of............ 46

Garnet-amphibolite, occurrence and description of..:.......................... 78

Glacial deposits, efl'ect 011 course of Housatonic River ........................ ' 15

extentof............................... 95

Glacial drainage, deflection of.............. 98

Glass sand, occurrence of .................. 100

Gneiss, blue-quartz, occurrence and oharac-

 tor of ........................ 27,37-39,72

micaceous, occurrence of............... 56

nodular, occurrence of.................. 65, 66

occurrence of.......................... 77

section at Washington showing occurof.................................. 36

Gold,.prospects of finding................ 101-102

Goose Pond anticline, description of........ 46

137
138 INDEX.

Goose Pond limestone, occurrence of ....... 51-52

Granite, extent and character of............ 99

occurrence of ........................... 77

Granulite, occurrence and character of..... 24

Graphite, occurrence of .................... 101

Greenwater Pond anticline, description of.. 45 

Gulf anticline, description of .............. 43-44

Harmou Pond area, description of.......... C2

Hayes Pond, bed of pyroxene-actiuolite at.. 46-47 

Hillebrand, W. F., analysis by.............. 67-68

Hinsdale anticline, conformity at.......... 70

description of.......................... 21-37

Hinsdale area, description of............... 20

Hinsdale fault, description of .............. 89

Hinsdale gneiss, occurrence and character

of................................... 22-27

section at Windsor..................... 29

section showing occurrence of.......... 41

thin section of......................... 26

occurrence of........................... 47,63

Hinsdale Lake, description of............... 96-97

Hinsdale limestone, occurrence and character of............................ 27-33,68

section at Aldeman quarry showing ... 43 

section at Windsor..................... 29

section showing occurrence of.......... 41

Hinsdale Valley, deflected glacial drainage

Hitchcock, E., analysis given by.......... 85

cited ............................. 27,42,52, 80

Hobbs, W. H., cited .................... 20,65,67

Hoosac area, description of ................ 19-21

Hop Brook anticline, description of ........ 46

Hop Brook limestone, occurrence of........ 52

Hornblende, occurrence of ................. 63

Hornblende gneiss, occurrence of.......... 56

Hornblende-schist, section showing occurrence of............................ 41

Hornblendic rocks, occurrence of.......... 75-76

Hotchkiss area, description of............. 62-63

Housatouic lliver, course of................ 15

. watershed between Connecticut River

and ........... .................... 14-15

Housatonic Valley, pre-Cambrian topography of ............................. 17

Ice, effect of recession on topography...... 96-97

Intrusive rocks, occurrence of............. 94-95

Iron ores, occurrence of.................. 100-101

Kames near Dalton ........................ 97

Kaolin, occurrence of...................... 80

Lee, analysis and strength tests of dolomite

from ............................... 99

analysis of limestone from............. 69

Lee gneiss, sections showing occurrence of. 41, 36 

occurrence and character of............ 33-34

Lee black gneiss, occurrence and character

of.................................. 48-49

Lee - Tyringham area, distribution and

character of........................ 44-55

Lenox fault, description of................. 93-94

Lenox Furnace, section east of... A........ 44

Limestone, analyses of..................... 69,87

effect upon topography of solution of.. 16-17 

metamorphosis of the pre-Cambrian... 54-55 

pinched into pre-Cambrian gneiss, section showing....................... 64

extent and character of ................ 98-99

Page. 

Magnetite, occurrence of................... 71

Marble, see Dolomite.

Merrill, G. P., cited on analysis and strength

of dolomite ........................ 99

Middlefield, analysis of limestone from .... 69

figure showing Cambrian gneiss folding 

over pre-Cambrian limestone unconformably ....................... 71

Mineral lexicon.......................... 103-127

Mineral resources....'..................... 98-102

Monterey area, limits and features of...... 60-61

Muddy Pond, Hinsdale limestone near..... 28

Muscovite-biotite-gneiss, occurrence of.... 67

Muscovite-gneiss, occurrence of ........... 67

New Marlboro, altitude at................. 14

section near.......... 1................. 61

New Marlboro area, description of......... 61-62

Nodules, analysis of........................ 68

North Canaan area, description of.......... '65

Otis area, limits and features of............ 56-58

Otis Center,bowlders in ................... 58

Paleozoic rocks, section of pre-Cambrian

and ................................ 18-19

Pegmatite, occurrence of................... 95

section showing occurrence of.......... 41

Peru, altitude near......................... 14

blue quartz gneiss at .................. 37

Plagioclase, occurrence and character of... 77-78 

Postglacial deposits, extent and charac

ter of........"....................... 95-98

Pre-Canibrian and Paleozoic rocks, section

of.................................. 18-19

Pre-Cambrian limestone, analyses of....... 69

Pre-Cambrian rocks, description of ........ 19-37

exposure on Bear Mountain'............ 58-59

outcrops of............................. 19-20

Pyroxene, occurrence of...............;.... 63

Pyroxene-hornblende, occurrence of ....... 64

Pyroxenite, occurrence of.................. 56,68

Pumpelly, R., reference to............... 13,19,35

Quartzitoon Ferncliff Ridge............... 86

Quartzite breccia, occurrence of............ 80

Richardson, C. H , cited on the Washington

limestone .......................... 17

River Bend Farm, Hinsdale limestone at... 28-29 

Road material, distribution of.............. 100

Rowe schist, description of................. 84

Sandisneld area, distribution of............ 55-56

Silurian quartzite, description of........... 88

Snowplow anticline of Bear Mountain,

description of...................... 58-60

Soapstone, occurrence and character of..... 100

South Daltou or Warner Mountain fault,

description of...................... 92-93

Southfield Cemetery area, description of... 62 

Steatite, figure showing occurrence of...... 30

occurrence and character of............ 30

Steiger, George, analysis by................ 87

Stockbridge limestone, analyses of......... 85

description of.......................... 84-85

section showing........................ 61,65

Suess, E., reference to ..................... 18

Tower, W. L., information furnished by.... 91

Tyringham area, description of ............ 20-21

Tyringham fault, description of............ 94
INDEX. 139

Tyringham gneiss, outcrops and character of 34 

section showing occurrence of.......... 36

Tyringham ligniform gneiss, description of. 49 

Tyringhain Valley, deflected glacial drainage iu.............................. 98

limestones in........................... 16

pre-Cambrian, topography of........... 16

Washington Basin, cause of ............... 95-96

Washington blue-quartz gneiss, description

of.................................. 49-50

Washington gneiss, figures showing thin

sections of .......................... 26

occurrence and character of............ 34-39

sections showing occurrence of... 36,61,65,66

Page. 

Washington Station, Hinsdale limestone

near................................ 28

section at lead mine near .............. 36

Warner Mountain fault, description of..... 92-93

Well borings at Dalton .................... 90,91

Westfield River, course of................. 15

West Norfolk Station, description of cut

near................................ 77

Weston Mills, wells at..................... 91-92

Windsor, section at........................ 29

Windsor Falls, figure showing steatite

quarry near........................ 30

Windsor mica-schist bed, description of ... 81 

Woltf, J. E., reference to.......... 13,19, 35, 38,94