/

DEPARTMENT OF THE INTERIOR

BULLETIN

7_/VOF T11K

IT NT TED STATES

GEOLOGICAL SURVE\7

ISTo. 8

ON SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS 

IN CERTAIN ROCKS.

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1 884

AX> "V B it TI S E M K N" T.

(BuUetin No. 8.)

The publications 'of the United States Geological Survey are issued in accordance with the statutes 

approved March 3,1879, which declares that 

"The publications of the Geological Survey shall consist of the annual report of operations, geo~ 

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On July 7,1882, the following joint resolution, referring to all Government publications, was passed! 

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Except, therefore, in those cases where an extra number of any publication is supplied to this office; 

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ANNUAL KEPORTS.

Of the Animal Keports there have been already published:

I. First Annual Report to the Hon. Carl Schure, by Clarence King. 1880. 8°. 79 pp. 1 map. JU. 

preliminary report describing plan of organization and publications.

II. Report of the Director of the United States Geological Survey for 1880-'81, by J. "W. PowelL.

1882. 8°. Iv, 588pp. 61 pi., 1 map. 

m. Third Annual Report of the United States Geological Survey, .1881-'82, by J. W. PowelL

1883.' 8°. xviii, 564 pp. 67 pi. and maps. . . 

IV. Fourth Annual Report of the United States Geological Survey, 1882-'83, by J. "W. PowelL.

1884. 8°. xii, 473 pp. 85 pi. and maps. ' } ' 

The Fifth Annual Report is in press.

MONOGRAPHS.

So far as already determined upon, the list of the Monographs is as follows: 

I. The Precious Metals, by Clarence Kong. In preparation.

IE. Tertiary History of the Grand Canon District, with atlas, by Capt. C. E. Dutton. Published". 

HI. Geology of the Comstock Lode and Washoe District, with atlas, by George F. Becker. PnB»- 

lished.

IV. Comstock Mining and Miners, by Eliot Lord. Published.

V. Copper-bearing Rocks of Lake Superior, by Prof. R. D. Irving. Published.

VI. Older Mesozoic Flora of Virginia, by Prof. William M. Fontaine. Published. 

VLT. Silver-lead Deposits of Eureka, Nevada, by Joseph S. Curtis. Published. 

V1LT-. Paleontology of the Eureka District, Nevada, by Charles D. Walcott. In press. 

IX. Brachiopoda and Lamellibranchiata of the Green Marls and Clays of New Jersey, by R. R 

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£2306
ADVERTISEMENT.

Geology and Mining Industry of Leadville, with atlas, by S. F. Emmons. In preparation.

 Geology of the Eureka Mining District, Nevada, with atlas, by Arnold Hague. In preparation.

Xake Bonneville, by G. K. Gilbert. In preparation.

Dinocerata: A monograph on an extinct order of Ungulates, by Prof. 0. C. Marsh. In preparation.

Sanropoda, by Prof. 0. C. Marsh. In preparation.

Stegosauria, by Prof. 0. C. Marsh. In preparation.

 Of these Monographs, Nos. II, III, IV, V, VI, and VII are now published, viz:

II. Tertiary History of the Grand Canon District, with atlas, by C. E. Dntton, Capt U. S. A. 1682.

4°. 264 pp. 42 pi. and atlas of 26 double sheets folio. Price $10.12. 

HI. Geology of theComstock Lode and Washoe District, with atlas, by George F. Becker. 1882. 4°.

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VI. Contributions to the Knowledge of the Older Mesozoio Flora of Virginia, by "William M. Fontaine. 1883. t°. xix, 144 pp. 541. 54 pi. Price $-.

VII. Silver-lead Deposits of Eureka, Nevada, by Joseph S. Cnrtis. 1884. 4°. xii, 200 .pp. 15 pi. 

Price $ .

Nos. VIII and LtC are in press and will soon appear. The others, to which numbers are not assigned, 

Are in preparation.

BULLETINS.

The Bulletins of the Survey will contain such papers relating to the general purpose of its work as 

do not properly come under the heads of ANNUAL BEPOBTB or MONOGRAPHS.

Each of these Bulletins will contain but one paper, and be complete in itself. They will, however, 

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Of this series of Bulletins Nos. 1, 2, 3, 4,5,6, 1, and 8 are already published, viz:

1. On Hypersthene-Andes!te and on Triclinic Pyroxene in Augitic Eocks, by Whitman Cross, with 

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Hew York, to Bradford,County, Pennsylvania, by Henry S. Williams. 1884. 8°. 36pp. Price 5 cents.

4. On Mesozoic Fossils, by Charles A. White. 1884. 8°. 36 pp. 9 pi. Price 5 cents.

5. A Dictionary of Altitudes in the United States, compiled by Henry Gannett. 1884. 8°. 325 pp. 

Price 20 cents.

6. Elevations in the Dominion of Canada, by J. W. Spencer. 1884. 8°. 43 pp. Price 5 cents.

7. Mapoteca Geologica Americana. A Catalogue of Geological Maps of America (North and South),

1752-1881, by Jules Marcou and John Belknap Marcou. 1884. 8°. 184 pp. Price 10 cents.

8. On Secondary Enlargement of Mineral Fragments in Certain Eocks, by E. D. Irving and C. E. 

Vanhise. 1884. 8°. 56 pp. Price 10 cents.

STATISTICAL PAPERS.

A fourth series of publications having special reference to the mineral resources of the United 

States is contemplated. Of that series the first has been published, viz: Mineral Eesources of the 

United States, by Albert Williams, jr. 1883. 8°. xvii, 813 pp. Price 50 cents.

Correspondence relating to the publications of the Survey, and all remittances, which must be by 

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DlHECtOR OP THE UNITED STATES GEOLOGICAL SURVEY,

Washington, D. 0. 

WASHINGTON, D. C., August 30,1884.
DEPARTMENT OF THE INTERIOR

BULLETIN

OF THE

UNITED STATES

No.'S

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1884
HURO.N1AN QUAKT2ITE OF NEEBISH ISLAND, EAST SIDE ST. MAR

(Tbe dip is towards the observer.)
CJNITED STATES GEOLOGICAL SUEVEY

J. "W. rOWELL DIRECTOR

ON

SECONDARY ENLARGEMENTS

OF

IN

CERTAIN ROOKS

BY

R. D. IRVING and C. R. VAN HISE

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1884

LETTER OF TRANSMITTAL

UNITED STATES GEOLOGICAL SURVEY,

Madison, Wis., April 1, 1884.

SIR : I Lave the honor to transmit herewith a paper on Secondary 

Enlargements of Mineral Fragments in Certain Rocks, prepared by myself and Assistant Geologist C. R. Van Hise.

The plates were all drawn from nature with the camera Incida, by 

Assistant Geologist W. N. Merriam.

I am, sir, very respectfully yours,

ROLAND B. IRVING, 

Geologist in Charge of the Survey of 

Pre-Cambrian Boclcs of the Northwestern States. 

Hon. J. W. POWELL,

Director United States Geological Survey,

Washington, D. G.

5 

(189)

CONTENTS.

Page. 

Letter of transmittal............ .........................^................ 5

Contents.................................................................. 7

List of illustrations ....................................................... 9

PART I. Enlargements of quartz fragments and genesis of qnartzites, by 

R. D. Jrving and C. R. Vanllise ......................................... 11

General considerations................................................ 11

List of localities of rocks examined, with brief descriptive notes........ 23

For Huronian rocks................................................. 23

In the typical Huronian of Lake Huron..... ..^.................... 23

In the iron-bearing series of Marquette, Mich ...................... 27

In the iron-bearing series of the Penokee region of Wisconsin....... 30

In the slates of the Saint Louis River, Minnesota................... 32

In the qnartzite formation of the Baraboo region of Wisconsin...... 33

In the qnartzite formation of Southern Minnesota ................. 34

In the Animikie series of Northern Minnesota, and the Thunder Bay

region of Lake Superior......................................... 35

In the folded schists of the national boundary line, north of Lake

Superior ........................................................ 37

For Keweenawan sandstones ........................................ 38

For Cambrian rocks................................................. 39

In the Grand Cafion group of the Colorado River .................. 39

In the Potsdam sandstone of the Mississippi Valley ................ 39

. In the Eastern sandstone of Lake Superior......................... 40

In the Western sandstone of Lake Superior ........................ 41

For Silurian rocks .................................................. 41

In the Saint Peter's sandstone of Wisconsin........................ 41

In the Eureka quartzite of Nevada ................................ 42

For Devonian rocks................................................. 42

For Carboniferous rocks............................................. 43

For Triassic rocks ......... .......... ....^........................... 43

For Cretaceous rocks.........'............... ........................ 43

PART II. Enlargements of feldspar fragments in certain Keweenawan sandstones, by C. R Van Hise ...............................'................... 44

PART III. Summary of general conclusions, by R. D< Irving ............... 48

(191)

ILI.TJST RATIONS.

To face page:

PLATE I. Huronian quartzite of East Neebish Eapids, Saiut Mary's River.. 1 

PLATE II. Crystal-faced enlargements of quartz fragments................. 13

FlG. 1. Single grain of the sandstone intercalated in Huronian quartzite

of East Neebish Island. Enlarged 67 diameters. No. 17 of

the list, p. 26. The outlines of the crystal faces were drawn

in from a dry mounting, after which the grain was covered

with balsam and the nucleal fragment drawn. 

FIG. 2. Another grain from the same sandstone, drawn from a balsam

mounting. Enlarged 67 diameters. 

FIG. 3. Single grain of the Huronian sandstone of Spnrr Mountain, Mich.

No. 30 of the list, p. 30. Drawn from a balsam mounting.

Enlarged 100 diameters. 

PIGS. 4, 5, 6. Single grains from the Potsdam sandstone of New Lisbon,

Wis. No. 87 of the list, p. 40. Balsam mounting. Enlarged

95 diameters. 

FIGS. 7, 9. Single grains of the Potsdam sandstone of the quarry on the

Torch Lake Railroad, Keweenaw Point, Michigan. No. 90 of

the list, p. 40. Enlarged 67 diameters! 

FIG. 8. Portion of a thin section of the same sandstone, showing how

nucleal fragments and enlargements polarize together.

Enlarged 67 diameters. The black spaces are holes in the -

section. 

PLATE III. Thin sections of quartzites .................................... 15

FIG. 1. Quartzite crust of Saint Peter's sandstone, Arlington Prairie,

Columbia County, Wisconsin. No. 95 of the list, p. 42. The

enlargements have often taken crystal faces. Ordinary light.

Enlarged 35 diameters.

FIG. 2. Arenaceous quartzite, Animikie series, Portage Bay Island, Minnesota, coast of Lake Superior. No. 61 of the list, p. 36.

Polarized light. Enlarged 45 diameters. 

PLATE IV. FIGS. 1 and 2. Thin sections of red qnartzite, Animikie group,

Prairie River Falls, Minnesota. No. 58 of the list, p. 35. The

same section in ordinary and polarized light. Enlarged 39 .

diameters.................................................. 23

PLATE V. Thin sections of sandstone and quartzite........................ 25

FIG. 1. Indurated Saint Peter's sandstone, Gibraltar Bluff, Columbia

County, Wisconsin. No. 96 of the list, p. 42. Polarized light.

Enlarged 35 diameters. 

FIG. 2. Huroniau quartzite of Neebish Island, Saint Mary's River. No.

12 of the list, p. 25. Polarized light. Enlarged 35 diameters.

9 

(193)
10 ILLUSTEATIONS.

To face page. 

PLATE VI, Thin sections of quartzite, &c................... .......... 29

. FIG. 1 (upper half). Huronian qnartzite from gaunister quarry, south 

side of Carp River, near Marquette, Mich. No. 22 of the list, 

p. 28. Polarized light. Enlarged 31 diameters.

FIG. 1 (lower half). Huronian quartz-schist from near Marquette, Mich. 

No. 27 of the list, p. 29. Polarized light. Enlarged 36 diameters. Designed to show schistose structure and induration 

by independently oriented quartz.

FlG. 2 (upper half). Red quartzite of Prairie River Falls, Minnesota. 

No. 58 of the list, p. 35. Enlarged 31 diameters. Polarized 

light. Drawn to show the enlargement of a complex grain. 

. FIG. 2 (lower half). Cherty Potsdam sandstone, Westfield, Sauk County, 

Wisconsin. Polarized light. Enlarged 35 diameters. A 

cherty matrix holds grains of quartz which have received 

enlargements.

(194)
J.

ENLARGEMENTS OF QUARTZ FRAGMENTS AND GENESIS

OF QUARTZITE8.

BY E. D. TRYING AND C. E. VAN HISE.

GENERAL CONSIDERATIONS.

In his address before the Geological Society of London, delivered 

February 20,1880,1 Sorby describes sands whose grains are bounded 

externally by crystalline faces, but have in the interior the ordinary 

rolled grains, ttie crystalline faces having been produced by a secondary deposition of quartz upon the irregular surfaces of the original 

grains. He shows also that the quartz coatings of these grains are in 

perfect "optical and crystalline continuity" with the interior fragments, 

each original fragment having thus been changed to a definite crystal.

He states further that he had examined crystalline sands from the 

sandstones of various ages "from the Oolites down to the Old Eed," and 

that they are commonly little coherent, but that in some specimens "a 

number of grains may often be seen cohering more strongly than the 

rest, and these show clearly that the cavities originally existing between the grains have been more or less completely filled with quartz. 

Moreover, on carefully examining the less coherent grains by surface 

illumination, we can see not only the planes and angles due to unimpeded crystallization, but also more or less deep impressions due to the 

interference of contiguous grains, thus proving conclusively that the 

deposition of crystalline quartz took place after the nuclei were deposited as a bed of normal sand. The very imperfect consolidation sometimes met with is, perhaps, not so very surprising when we reflect on 

the very small coherence of many large quartz crystals which are yet 

in close juxtaposition. However, it does seem probable that this crystallization of quartz sometimes contributes very materially to the 

cohesion of the grains in hard and compact quartzites. In such 

examples as the Gannister of the South Yorkshire coal-field we can 

see in a thin section that the grains fit alongside one another in a 

very striking manner, and it-is only by extreme care that good proof, 

can be obtained of the actual deposition of quartz between them. 

However, in the case of a highly consolidated sandstone from Trinidad the proof of the deposition of quartz is as complete as possible; 

i-Proc. Geol. Soo. Lond., 1880, p. 62.

(195) 11
12 SEGONDAEY ENLARGEMENTS OF MINERAL FRAGMENTS. [HULL. 8.

the outline of the original grains of sand is perfectly distinct, and the 

cavities between them are filled with clear quartz in crystalline continuity with the contiguous grains; so that the whole is a mass of interfering crystals, each having a sand-grain as a nucleus. The rock 

has thus been converted into a hard quartzite, almost like a true quartz 

rock, but differs from such quartz rocks as those of the Scotch Highlands in containing no mica crystallized in situ. All my specimens of 

these quartz rocks are really highly quartzose mica-schists; and, so far, 

I have failed in my endeavors to trace the connection between them 

and true sandstones, though possibly this could be easily done in some 

districts which I have not examined."2

In the American Journal of Science for July, 1881, A. A. Young 

describes a sandstone from the Potsdam sandstone of New Lisbon, Wis., 

the rolled grains of which are enveloped in secondary crystal-faceted 

quartz coatings. In the same journal for June, 1883, the senior author 

of this paper showed what Sorby regards as probable, viz: that the "cohesion of the grains in hard and compact quartzites" is due to this deposition of interstitial quartz, to be certainly true in the cases of certain 

quartzites and mica-bearing quartz-schists of Archaean (Huronian) a-ge. 

He also showed that irregular areas, often of very small size, and even thin 

crusts, due to a mere weathering, occur frequently in the Saint Peter's 

and Potsdam sandstones of Wisconsin, in which these sandstones have 

been changed to vitreous quartzites by the same mode of induration, i. e., 

by the deposition of an interstitial quartz which has divided itself off 

into interlocking areas optically continuous with the original grains of 

quartz sand.

2 So-called "crystallized" sands and sandstones have been described by many 

authors, beginning with Gerhard, in 1816, but none of them, so far as we have yet 

learned, understood that the crystal-faced grains were rolled fragments enlarged by 

secondary deposition. The idea with regard to these sandstones appears to have been 

that their crystal-faced grains were wholly separated out from solution, and the sandstones not really of clastic origin. Zirkel (Petrographie, II, p. 575) says of these crystallized sandstones that they "vielleicht gar nicht zu den Idastischen Gesteinen 

gerechnet werden diirfen." See also Naumann's Geognosie, I, p. 530, and Von Cotta's 

Lithology, Lawrence's translation, pp. 296,301. Zirkel (Petrographie, II, p. 590) gives 

a number of references among the older writers, but so far as I have been able to refer 

to them none seem to have had any idea of the true nature of the crystals.

Daubre'e, who described the Yosges crystal-bearing sandstone as long ago as 1852, 

has quite recently (Eludes Synthe"tiques de Gdologie Experi men tale, 1879, pp. 226-230), 

in a re'sume" of earlier observations by himself and others (Elie de Beaumont, Hoffmau, Gutberlet, Croisnier) on crystallized sands, stated distinctly his belief in theirpurely chemical origin. The Vosges sandstone, which is mentioned by Sorby (loc. 

cit.) as an admirable instance of the formation of crystallized sands by the enlargement of rolled grains, Daubre'e cites as a typical instance of a sandstone of chemical origin. While admitting the occurrence of instances where it is difficult to see 

any such connection, he advances the view that, in. the cases of the Vosges sand and 

many others, the deposit of crystals of quartz has been derived from a solution of an 

alkaline silicate supplied to the sea by the decomposition, before complete cooling, of 

masses of eruptive feldspathic porphyry, or of porphyry tuffs a view which receives 

no substantiation from our own observations.

(196)
U.S. GEOLOGICAL SURVEY. BULLETIN No.8.PL.1C

CRYSTAL-FACED ENLARGEMENTS OF 9UARTZ FRAGMENTS.
IKYING AND VAN iiisE.] ENLARGEMENTS IN LOOSE SANDSTONES. 13

The latter observations were made in the beginning of 1883, but in 

ignorance of Sorby's results, announced some years before. Several other 

lithologists had in the mean time made similar observations. In the 

summer of 1881, Arnold Hague and Iddings noted this form of induration in the Silurian, Devonian, and Carboniferous quartzites of the 

Eureka district of Nevada, and Mr. Iddings prepared some drawings 

at the time which will appear in Hague's monograph of that district.3 

Bonney, Phillips, and others have made1 similar observations in Europe.4 The peculiar induration due to weathering had also been previously observed both in Europe and in this country,5 although it 

does not appear that the exact nature of the induration was in any 

case understood.

Since the publication, by the senior author of this bulletin, in the 

American Journal of Science, above referred to, we have been engaged 

in studying sandstones, quartzites, and other rocks from various formations, with a view of determining how widespread this mode of induration is. Our attention has been mainly turned to rocks of preCambrian age, but, whenever we have been able to procure the material, we have studied also rocks of more recent formations down to 

the'Cretaceous. From the list given below it will be seen that we have 

found this peculiar form of induration in rocks representing nearly all 

of the various Hurouian areas of the Northwest, as well as in a number 

of quartzites and sandstones of various degrees of induration from the 

later formations. We have also noted a number of interesting new 

points in this connection.

The most important result of our study is, of course, the proving 

that most, if not all, of the ancient quartzites, as well as many of the 

quartziferous schists, are composed in the main of the original fraginerital material, unaltered save by some of the ordinary metasomatic 

processes, but the fragments cemented together by a very subordinate 

quantity of a siliceous cement of secondary origin. This siliceous cement 

forms the only part of the rock that has crystallized in situ, the more or 

less intricate interlocking of its areas and its common optical continuity 

with the original quartz fragments giving rise to a deceptive appearance of complete original crystallization.

The least advanced condition of this process of induration is to be 

met with in sandstones that are quite loose, as was shown by Sorby. 

The rolled grains of quartz are each furnished with a border of newly 

deposited quartz, optically continuous with the nucleus, and furnished 

with more or less perfectly developed crystalline faces. At times the 

fragment is only partially buried by the newly deposited border, this 

being especially true of the more irregularly outlined grains, but more

? Monographs of the United States Geological Survey, not yet issued. 

4 Q. J. G. S., Vol. XXXIX, p. 20.

6A. Geikie, Text Book of Geology, pp. 158,333. M. E. Wadsworth, Science, Vol. I, 

p.146.

(197)
14 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. IBULL. 8.

usually the grain is completely, though very thinly, covered, so that 

we have thus formed a quite perfect quartz crystal, whose greater part 

is, in each case, mainly composed of the old and worn grain. These 

crystal-faced borders we have observed running in thickness from films 

so thin as to be barely perceptible with the microscope to those 0.2 

or 0.3mm. in width. The presence of these crystal faces makes the surface of the sandstone affected by this induration sparkle and glisten 

like a frosted surface. Such crystalline sandstones have been known 

for a long time, and they are common in all formations from the Archaean to the Tertiary. Indeed, since our attention was first drawn to this 

matter, it has seemed to us as if the presence of at least some of the crystalline faces in quartzose sandstones is rather the rule than the exception. There can be no doubt, we think, that all owe their sparkling appearance to this same process of secondary enlargement of the original 

fragments. The crystalline faces are best developed, as already said, 

in loose sandstones, where the induration has not gone far enough to 

produce much interference, but they may coexist with a considerable 

degree of induration. The crystal-faced enlargements of the fragments 

in such sandstones may generally be separated from the nucleal grains 

by the presence of films of iron oxide on the surfaces of the nuclei, by 

the greater freedom from inclusions of the newly deposited as compared 

with the nucleal quartz, by the existence of a roughened surface on the 

inner grain, and by rows of cavities at the junction of the new quartz 

with the corroded surface upon which it was deposited.

Cases are met with in which it is exceedingly difficult to separate the 

two quartzes from each other. Sorby6 mentions as such an instance the 

" Gannister" of the South Yorkshire coal field, and in our own experience we have met with two instances, those of the Huronian sandstones of Spurr Mountain, Michigan, and Penokee Gap, Wisconsin, 

both of which are alluded to in the list given below. The difficulty in 

all these cases arises from the great relative purity of the original 

quartz particles and the entire absence of an iron oxide coating to the 

nuclei, and, in the last two cases at least, from the smallness of the 

grains; but, in all, careful search discovers grains in which the separating lines may be perceived; and no doubt remains that in these 

cases also the crystals are enlargements of rounded fragments. These 

observations are of particular interest, since they render it evident that 

a completely indurated rock, apparently made up entirely of originally 

deposited quartz, may yet be only apparently so, the lines of separation 

between the new and old material being imperceptible.

In the very loose sandstones the nuclei and deposited quartz are best 

distinguished from one another by mounting the sand crumbled from 

the rock in balsam, while the crystalline faces are best seen in a dry 

mounting of this sand.

The whole process of enlargement in these crystal-bearing sandstones 

is of course, as Sorby shows,7 precisely analogous to what is known to

6 LQC cit., p. 63* T LOG cit.. p. 62,

(198)
U.S. GEOLOGICAL. SURVEY BULLETIN No.8, PL.Iff

THIN SECTIONS OF QUARTZITES.
IHVISG AND VAN BIBB.] ENLARGEMENTS IN LOOSE SANDSTONES. 15

occur when a crystal of a soluble salt is placed in an evaporating saturated solution of the same substance. We have tried this experiment 

with fragments, from one-eighth inch to one-half inch in diameter, of 

alum (K2 A12 (S O4 )4 ), nickel ammonium sulphate ( (N H4 )2 Ni (S O4 )2,) 

and sodium and potassium tartrate (Na K (C4 H4 O6).) The fragments 

in each case were thoroughly rounded and coated with iron oxide. Being then hung each in its appropriate solution, the angles and faces 

were soon rapidly developed, after which the crystal continued to grow 

over the whole surface. Sections made from these crystals showed the 

nuclei bounded by oxide of iron films and built out by newly deposited 

material with precisely the relations met with in the enlarged grains of 

crystal-bearing sandstones.

As instances of localities yielding sandstones with crystal-faceted 

grains may be mentioned the following: For Hnronian sandstonesEast Neebish Island, St. Mary's Eiver, Canada; Spurr Mountain, 

Michigan; Penokee Gap, Ashland County, Wisconsin; Devil's Lake, 

Sauk County, Wisconsin; Bedstone, Nicollet County, Minnesota. For 

Potsdam sandstone: New Lisbon, Juneau County, Wisconsin; the 

great bluff known as Eoche Edit, Adams County, Wisconsin, and the 

railroad cut on the Chicago and Northwestern road just south of Madison.8 For St. Peter's sandstones Arlington Prairie, Columbia County, 

Wisconsin; Lancaster, Grant County, Wisconsin.

Plate II shows a number of instances of crystal-faced enlargements 

of quartz fragments. Fig. 1 of this plate shows a single grain of the 

sandstone intercalated in the Huronian quartzite of East Neebish Island, 

St. Mary's Elver, enlarged 67 diameters. The outlines of the crystal 

faces, which are more or less interrupted from lack of material, were 

drawn in from a dry mounting of the grain, after which it was covered 

with balsam, and the nucleal fragment, with its oxide of iron coating, 

drawn. Fig. 2 shows another grain from the same sandstone, enlarged 

67 diameters, as seen in a balsam mounting. Fig. 3 represents a single 

grain from the Huronian sandstone of Spurr Mountain, Michigan, as 

seen in a balsam mounting. The enlargement is 100 diameters. Figs. 

4, 5, and 6 show the appearance, in the balsam mounting, of single 

grains from the Potsdam sandstone of New Lisbon, Wisconsin, enlarged 

95 diameters. Fi'gs. 7 and 9 are similarly mounted single grains from 

the Potsdam sandstone of the quarry on the Torch Lake Eailroad, Keweenaw Point, Michigan, enlarged 67 diameters. Fig. 8 is a portion of 

a thin section of the same sandstone, also enlarged 67 diameters, and 

drawn as seen between the crossed nicols, with the object of showing 

how the nucleal fragments and enlargements polarize together. The 

black lines on two of the grains in this figure indicate the positions of 

the elasticity axes. The black spaces are holes in the section.

8 This is the layer described in the Wisconsin reports under the name of the Madison 

sandstqne. The occurrence of crystal-faceted grains in the more siliceous and looser 

portions of this layer appears to be an all but universal phenonienon in Southern Central Wiscppsin,

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16 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. IBULL. 8.

A more advanced condition of induration is met with in certain sandstones, which, while still showing to'some extent the crystalline facets, 

have the secondarily deposited quartz areas more generally interfering 

. with one another. This may be seen in much of the Huronian quartzite at Neebish, Saint Mary's Biver; Bedstone, Minn.; and Devil's Lake, 

Wis. at all of which localities may be seen rapid transitions from the 

loosest sandstone to the most compact and vitreous quartzite, as also' 

in much of the Potsdam sandstone of the interior of Wisconsin, for 

instance the rock quarried, at Grand Eapids, Black Eiver Falls and 

Packwaukee. Fig. 1 of Plate III is drawn from a section of the vitrified crust of the St. Peter's sandstone of Arlington, Columbia County, 

Wisconsin. This crust, which is decribed somewhat fully on a subsequent page, is immediately below the surface without crystalline 

facets, the enlargements having interfered too thoroughly. But at a 

depth of one-fourth to one-half an inch the crystal facets begin to grow 

plentiful, until the loose sandstone is reached at the depth of about an 

inch or two, when every grain is furnished with the facets. The figure 

referred to shows one of the intermediate phases where there has been 

some interference, but crystal facets have been enabled to form in a 

number of places. The outlines of the nucleal grains are distinctly but 

not strongly marked. The brown filling material is.oxide of iron.

A still more advanced stage of induration, but yet one which is still 

short of complete vitrification, is met with in those quartzites, which, 

while retaining something of a granular or arenaceous appearance, are 

yet without any of the crystalline facets, the interference of the secondary quartz areas having been general. An excellent instance of this is 

the sandstone from Gibraltar Bluff, Columbia County, Wisconsin. Much 

of a similar material occurs in the Huronian quartzites of the north 

shore of Lake Huron, of Marquette, Mich., and of Southwestern Minnesota. The Gibraltar Bluff rock is shown at Fig. 1 of Plate V, which 

represents part of a thin section, as seen in the polarized light, enlarged 

35 diameters. A more arenaceous quartzite, but still one without crystal faces, is shown at Fig. 2, Plate III, which represents a thin section of 

the sandy Auimikie quartzite of Portage Bay Island, Minnesota. The 

enlargement is 45 diameters, and the section is represented as seen in the 

polarized light. It will be noted that the enlargements of the grains 

are at times unusually broad.

In the most completely vitreous quartzites the arenaceous or granular appearance is entirely lost, the particles being fused into an apparently homogeneous mass, which appears both to the naked eye and under 

the microscope to be wholly composed of originally deposited, intricately 

interlocking areas of quartz. But closer study of the sections of such 

quartzites shows that, like those previously described, they are made up 

partly of fragmental material and partly x>f a secondarily deposited

(200)
IKVING AND VAN HISE.] ENLARGEMENTS IN VITEEOUS QUARTZITES. 17

quartz, the interlocking areas of the latter being in large measure 

optically continuous with the original fragments, but also at times in 

part independent of them. The degree of intricacy of the interlocking 

of the areas of the secondary quartz will be found to vary greatly in 

different quartzites., At times these areas will meet each other along 

quite straight or only slightly curved lines, and again they will dovetail into each other in the most intricate manner. As a type of the 

most completely vitrified quartzites, may be mentioned the " gannister" 

of Marquette, Midi., No. 22 of the list below. A thin section of this' 

rock, as seen in the polarized light, and enlarged 31 diameters, is represented.in the upper half of Fig. 1, Plate VI. It will be seen that the enlargements are often unusually broad and dovetail with each other somewhat intricately. Other vitreous quartzites are shown at Fig. 2, Plate 

V; Figs. 1 and 2 of Plate IV, and the upper half of Fig. 2 of Plate VI. 

The last three of these figures represent the red Animikie quartzite 

of Prarie Biver Falls, Minnesota. The rock of this place is described 

as being much of it sandy, but the specimen furnished us by the kindness of Prof. Is. H. Winchell shows a quartzite in which but little of an 

arenaceous texture remains. Two of the figures are drawn from the section as seen in the polarized light, in order that the extent of the enlargements may be seen. It will be observed that in places they dove-tail 

quite intricately and the outlines of the very round nucleal fragments 

are rendered beautifully distinct by the fringes of oxide of iron.

The proportion of the infiltrated quartz which has crystallized independently of the original fragments varies very greatly in different 

cases. At times most of it, or even all, seems to occur in this form, the 

interstices between the much-rounded fragments being entirely filled 

with a secondary quartz in minute intricately interlocking areas, wholly 

independent of the original grains. As instances of rocks in which the 

independent deposition of quartz is the chief or only indurating material, may be mentioned the foot-wall rock of the Champion Mine, Michigan, much of the quartzite of the great range immediately east of 

Marquette, Mich., and the red quartzite of McClennan's Landing on 

the north shore of Lake Huron. From these extreme cases there are 

all phases down to the cases where all of the secondary quartz occurs 

as enlargements of the original fragments.

Thin sections of quartzites in which the fine interstitial quartz is 

present are not easily represented by figures. At the lower half of 

Fig. 1, Plate VI, an attempt is made to represent the Huronian quartzschist from near Marquette. The section is drawn as seen in the polarized light and is enlarged 36 diameters.

In some cases where the enlargements of the original grains and the

independently oriented quartz occur together, the enlargements present

the appearance of fading out gradually into the finely interlocking in-

. terstitial material. This appearance arises from the fact that as the

original fragment is receded from, less and less of the interstitial quartz

Bull. 8 2 (201)
18 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

is optically continuous with it, while more and more is separated out 

into relatively minute independent areas. It is thus evident that all 

of the interstitial quartz, including both that which is in independent 

areas and that which is oriented with the original fragments, has been deposited simultaneously, the crystalline influence of the fragment having 

lessened rapidly in power .as the distance from the fragment increased. 

In those cases where all the interstitial quartz has been deposited independently of the original grains, the deposition went on too rapidly 

for those grains to exert their influence. The apparent fading out of 

quartz fragments also arises from another cause in the cases of certain 

argillaceous quartzites mentioned below.

In certain quartzites, that interstitial silica which has been deposited 

independently of the original fragments has in part separated out as 

chalcedonic or entirely amorphous silica. In fact, there is every gradation found in some of these cases from that quartz which is in independent areas of some-little size, through more and more finely divided 

kinds, to that which is completely amorphous, presenting no perceptible effect when revolved between the crossed nicols. The amount of

s

this cherty silica present varies between wide limits, in some cases 

predominating over the quartzose material, when the rock belongs more 

properly with the chert and chert-schists, which are considered separately below. The lower half of Fig. 2, Plate VI, shows the appearance 

in the polarized light of a thin section of a cherty Potsdam sandstone 

from Westfield, Sauk County, Wisconsin, enlarged 35 diameters. Most 

of the rock is taken up by the cherty matrix, but in this are buried 

quartz fragments of various sizes which have received small enlargements. The appearance of the upper side of the largest quartz grain 

of the figure suggests that it may have been dissolved away.

Commonly the quartz fragments of a sandstone or qnartzite are fragments of single quartz individuals, but cases often occur where they 

are themselves complex, i. e., made up of several or many differently 

oriented, interlocking areas. We have noted a number of cases where 

such complex grains have been enlarged, and in such cases the added 

quartz is divided off into areas oriented each with the part of the original grain with which it is in contact. This is very beautifully seen in 

the large grain of the upper half of JFig. 2, Plate VI, which is drawn 

from the red Aniinikie quartzite of Prairie River.

So far we have considered rocks that are purely quartzose, or nearly 

so, and it is in these that the enlargement of the quartzes is most striking, and generally most readily made out, but we have observed it 

also in a large number of rocks where the detrital material is composed 

more or less largely of other minerals than quartz, and even in cases 

where the quartz is a rather sparse accessory. A large part of the 

thickness of the original typical Huronian of Lake Huron is made-up 

of gray to black fragmental rocks, grading from very coarse-grained 

 (202)
IBNISG ASD VAN mm.] ENLiRGEMENTS IN GREYWACKES. ' 19

kinds to those that are almost aphanitic. These rocks Logan called 

collectively, on account of their frequently containing pebbles of various 

kinds, by the name of " slate conglomerates." This name, however, covers kinds which differ much from each other. Some are almost pure 

quartzites, with a slight mixture of feldspathic fragments. In other 

cases the feldspathic fragments predominate, and in the finer kinds 

have often been decomposed to a clayey material, when the rocks 

become clay shales or slates. Most of the kinds, except those that are 

nearly purely quartzose, have undergone a considerable amount of 

metasomatic change, the principal result of which has been the production from the feldspars of a chloritic ingredient, whence chiefly the dark 

and often greenish hue presented by these rocks.

In all of the sections of these rocks examined by us evidence has 

been found of the secondary deposition of interstitial quartz. In a few 

cases this interstitial quartz has been deposited independently of the 

original quartz fragments, but oftener is more or less generally co-ordinated with them. Not only have the quartz areas of these rocks been 

enlarged, but the feldspar fragments also often present indications 

of similar enlargement.9 The complex character of these rocks, the 

metasomatic alteration which they have undergone, their dark color, 

and the siliceous paste by which they have been permeated, place them 

among "greywackes,"10.whilst the finer-grained and more fissile kinds 

are " greywacke-slates." These greywackes, which are, next to the 

quartzites, the most characteristic and important rocks of the type 

Huronian, are all "recomposed" rocks, and often, especially where the 

secondary quartz is abundant, and the alteration from feldspar to 

chlorite has progressed far, are not far in appearance, either macroscopically or microscopally, from true crystalline rocks, and would ordinarily be classed as metamorphic. Nevertheless they have undergone 

no other alteration than that which is involved in the secondary enlargement of quartz and feldspar particles, the metasomatic change of feld-. 

spar to chlorite, and the interstitial deposition of independently oriented 

quartz; and all of those changes are such as may be met with in the 

more recent and so-called unaltered formations. Indeed, we may say, 

setting aside those changes to be met within the immediate vicinity of 

the contact with eruptive materials, that in the typical Huronian,'i.e., 

that mapped by Logan as extending from the Saint Mary's to the Mississaugi Eiver on the north shore of Lake Huron, there has been no 

other kind of alteration of sediments than this, the various greenstone 

beds'of the series being taken as of eruptive origin.

Greywackes and greywacke-slates, with characters in each case of 

their own, but in general similar to those of the Lake Huron series, we 

have examined from the Animikie series of the region of Thunder Bay, 

and thence' westward along the national boundary line, from the Huro9 See infra, p. 27. 

*° Geikie's Text Book of Geology, p. 159.

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20 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

nian of the Penokee region of Wisconsin, and from the folded slaty series of the region of Knife Lake on the national boundary line. All of 

these are plainly fragmental, being composed mainly of quartz and 

feldspar fragments, and permeated to a marked degree by a quartzose 

cement whose areas are always more or less generally optically continuous with the original quartz particles. A belt of rocks, composed of 

dark-colored sandstones and shales, which would come under Geikie's 

definition of greywackes and greywacke-slates, forms a prominent member of the Keeweenaw series between Keeweenaw Point and Bad Eiver 

in Wisconsin, reaching a particularly large development in the region 

of the Porcupine Mountains. This is the belt which we have elsewhere 

described under the name of the Nonesuch Belt.11 In many sections 

of this rock an interstitial quartz, occurring as enlargements of the original particles, is met with, and is particularly abundant in sections from 

that portion of the Porcupine Mountains known as the Iron Eiver Silver Belt. 12 These greywackes, and particularly those of the silver 

belt, are no less metamorphic than the greywackes of the type Huronian, and yet they occur interstratified in a great thickness of unaltered 

sandstones. Moreover, they lie in that series many hundred feet above 

the latest of the great flows of eruptive material which characterize it, 

so that the alteration can in no way be attributed to igneous action.

Argillaceous rocks are not promising ones for the discovery of enlargements of quartz particles, and yet we have noted in them a number 

of instances of such enlargements, as, for example, in the cleaved slates 

of the Saint Louis Eiver region of Minnesota, and in the Marshall Hill 

schists of the Upper Wisconsin Valley, in Central Wisconsin.13 Mention 

has.been made in a preceding paragraph of the peculiar way in which 

the enlargements of quartz fragments in certain quartzites are made to 

appear as if fading off gradually into the fine interstitial material. A 

somewhat similar appearance, but one which is evidently due to a quite 

different cause, is met with in these argillaceous rocks, in which the enlargements of the widely separated quartz fragments have enveloped, 

in the process of growth, portions of the clayey matrix.

In nearly all of the schistose areas of the Northwest which have been 

by us or other geologists.referred to the Huronian, cherty rocks that 

is, rocks more or less largely composed of a chalcedonic or amorphous 

silica form considerable thicknesses. They are present in the Animikie 

series of the Thunder Bay region, in the folded slates of the region 

farther north, in the original Huronian of Lake Huron, in the ironbearing series of the Marquette and Menomonee regions of Michigan, 

and in the Penokee and Wisconsin Valley regions of Wisconsin. At 

least some of the jaspers associated with the " jaspery iron ores" are of

"Copper-bearing rocks of Lake Superior. Monographs of the U. S. Geological 

Survey, Vol. v, pp. 220-224. 

 Loc. cit., p. 221. 

13 Geology of Wisconsin, Vol. IV, pp. 668, 681 to 683.

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ENLARGEMENTS IN CHERTS IN MICA-SCHISTS. 21

this nature. We are still engaged in a general study of these cherts, 

jaspers, etc., and are not yet prepared to give a systematic account of 

them. But there are several features that we have noted in regard to 

them that are of interest in the present connection. At times these 

cherts are for a considerable thickness wholly composed of chalcedonic 

silica, but in other-cases they contain fragments of quartz, in smaller 

or greater quantities, up to a predominating amount. In such cases we 

have frequently noted that the quartz fragments are enlarged in the 

ordinary manner. ,. These cherts seem, in part at least, to be of direct 

chemical origin, and the appearance in the thin sections is as if the 

quartz.fragments had taken an enlargement of quartz simultaneously 

with the deposition of the mass of the amorphous silica. In these cherty 

rocks the enlargements of quartz fragments present the appearance of 

fading away gradually into the matrix material in a manner similar to 

that already noted in the case of certain quartzites, where the appearance has been explained by the lessening of the crystalline influence of 

the original particles, and the formation of more and more of independently oriented matter, as they are receded from. Here, however, we 

find a gradation all the way from the areas deposited so as to be 

optically continuous with the original quartz fragments, through a fine 

interlocking, independently oriented quartz, to the chalcedonic material. 

There are many.points as to the origin of these cherts which are yet 

obscure, chiefly because of the small amount of microscopic study given 

to them. We think, however, that it may be taken as certain that the 

Huronian cherts have in considerable measure originated in the same 

way as the cherts of the later formations. In the Potsdam sandstone, 

for instance, at a number of points in the region of the Upper Baraboo 

River, in Central Wisconsin, layers of sandstone are to be noted which 

are highly impregnated with chert, and in which at times the chert even 

predominates over the sand. Chert is ordinarily thought of as a characteristic of limestone formations, but the cherts of this region are 

wholly below and independent of any limestone formation. Evidently 

these cherty layers have been produced by the secondary deposition 

from solution of the interstitial cherty material, and they do not appear 

to differ, either as to the nature of the material or as to its origin, from 

some of the true Huronian cherts. These Potsdam cherty sandstones 

give interesting sections, in which the interstitial secondarily deposited 

material presents every degree of coarseness, from large areas optically 

continuous with the original quartz fragments to the finest, most completely non-polarizing amorphous silica.

Our sections of true mica schists are not yet very numerous, but we 

have found unmistakable enlargements of quartz fragments in the 

mica-schist forming part of the " Lower Quartzite" of Brooks, north of 

the Michigamme mine, Marquette region, Michigan, and in the more 

quartzitic portions of the upper mica-schist member, Formation XXI, of

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22 SECONDAEY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

the Penokee Huronian.14 This member of the Penokee series is plainly 

the equivalent of the upper mica-schist member of the Marquette 

Huronian.15 The latter mica-schist is finely displayed among the islands 

at the outlet of Michigamme Lake, where it is often plainly of an arenaceous appearance, but so far our sections have failed to prove the 

existence of secondary enlargements of quartz fragments in them, 

although what appears distinctly to be fragmental quartz is seen in 

these sections. The larger part, .however, of the quartz present is 

fine and clear, so that it is difficult to determine whether it is wholly 

an originally deposited quartz or is a finely fragmental material, the 

particles of which are now so enlarged as to interlock.

A general fragmental appearance is not uncommon in the mica-schist 

sections that we have examined, while the presence, in some kinds at 

least, of very strongly marked and unmistakable sedimentary deposition 

bandings traversing the schistose or slaty cleavage directions is sufficient 

proof that in such cases the material is mainly of fragmental origin. But 

so far as our investigations have progressed we have only in a few cases 

been able to prove the enlargement of quartz fragments by secondary 

deposition. It seems probable, however, that in many cases where 

their existence cannot be proved the enlargements exist. In such 

cases we may suppose that they cannot be seen simply because of the 

absence of a bordering material or of rough-ened surfaces to the original 

fragments. None of the mica-schists above referred to are like those 

which approach the gneisses in character. The latter have often as a 

characteristic feature large flattened areas of quartz lying in the planes 

of foliation. We have not as yet examined any such rocks in this connection.

Below we give a list of the various localities of rocks in which we 

have discovered the secondary enlargements of quartz fragments. The 

induration of the rocks of these places is in most cases mainly due to 

the presence of these secondary enlargements, the remainder of the 

material being fragmental, but cases are included where, as explained 

above, the indurating silica has been separated out in part independently. The list does not represent nearly all of the sections in which 

this indurating quartz has been found. Often a number of sections from 

the rocks from one general neighborhood have been examined, but the 

locality is only referred to once. We have classified the localities (1) 

according to the general position of the rocks in the geological series; 

(2) according to geographical distribution; and (3) according to the 

lithological characters. Brief descriptive notes are added in each case.

i4 Geology of Wisconsin, pp. 145-149.

16 Geological Survey of Michigan,Vol. I, p. 113. Geology of Wisconsin, Vol.Ill, p. 165.

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THJN SECTION OF RED OUARTZITE
IKVING AND VAN HIM.] ENLARGEMENTS IN HURONIAN ROCKS. 23

LIST OF LOCALITIES. 

HURONIAN EOCKS.

IN THE TYPICAL HURONIAN REGION OF LAKE HURON.

A.. Vitreous Quartzites.

1. Island two miles east of Thessalon Point, north shore of Lake Huron.

(Logan's "3 a," « Grey Quartzite."14 )

A feldspathic quartzite, holding many granite pebbles and boulders. Rounded to 

angular fragments of quartz, orthoclase, and oligoclase, with a fine interstitial material, partly of the same nature and partly kaolinitic, make up most of the rock, 

but the induration is plainly due to secondary enlargements of the quartz fragments, 

the enlargements being narrow, and not interlocking intricately. In places the angularity and abundance of the feldspar fragments, the occurrence of granite fragments, including both feldspars and quartz, and the presence of-the secondary enlarging silica, produce a rock which is macroscopically and microscopically similar 

in appearance to granite or gneiss. (Slides 1071 to 1079 inclusive.)

2. Islands 3£ miles northwest of Thessalon Point, north shore Lake 

Huron. (Logan's " 3 c," u White Quartzite.")

A feldspathic quartzite. Quite intricately interlocking quartz areas make up the 

larger part of the rock, but the interlocking is plainly due to the enlargement of 

rounded fragments, whose outlines are here and there plainly to be seen. There is 

also much of a fine interstitial independently deposited silica, which here and there 

approaches very close to, if.it does not reach, the amorphous form. (Slides 1183, 

1184.)

3. Mainland, four miles northwest of Thessalon Point, north shore Lake 

Huron. (Logan's " 3 c," « White Quartzite.")

A vitreous, white to brown quartzite conglomerate, in which the pebbles, 1 to 2 

inches in diameter, are of white quartz and black chert, with rarer ones of red jasper. The matrix is composed of the same materials, along with fragments of feldspars. The induration has been chiefly by enlargement of the quartz fragments, 

among which are some originally complex. These have taken complex enlargements. 

The bounding lines of the original quartz fragments are only now and then perceptible. The larger pebbles of .quartz do not seem to have taken any enlargements. 

There is also some fine independently deposited interstitial silica and a good deal of 

interstitial clayey material and flakes of chlorite, the latter probably a result of metasomatic change of the feldspars. (Slides 1185 to 1188 inclusive.)

4. Islands off east side Bruce Mine Bay, Lake Huron. (Logan's " 3 c," 

" White Quartzite,")

A light-colored feldspathic quartzite, much like the last described, but with these 

differences : the quartz areas interlock much more intricately; the division lines between the original grains and enlargements are still more rarely visible, being plain 

in only two or three out of some twenty sections; the feldspars are much more abundant, and include microcline and plagioclase, as well as orthoclase. This rock has 

plainly received a larger quantity of siliceous cement than the last described. The 

abundance of feldspars, the presence of plagioclases, the intricate enlargements produced by secondary quartz, and the presence of much chlorite as a result of the alteration of the feldspars, all combine to produce a strong resemblance to some gran-

( 16 ) See Atlas to Geology of Canada, 1863, Plate III, for Logan's subdivisions of 

the original Huronian.

(207)
24 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

ifcic rocks. The specimens are mostly taken from the neighborhood of some of the 

numerous dikes with which the rock is riddled, which may possibly have something 

to do with the large amount of siliceous cement and the consequent granitic appearance presented by this rock. (Slides 1191, 1192, 1194, 1196, 1197, 1201 to 1205 inclusive.)

5. North side of Campement d'Ours Island, Lake Huron. (Logau's 

" 3 f," « Upper Slate Conglomerate.")

A red feldspathic quartzite, the feldspars including both orthoclase and plagioclase, the two together making up.fully one-half of the rock. The quartz fragments 

are much enlarged, the enlargements interlocking with each other and with the feldspars somewhat intricately. There are present interstitially kaolin, chlorite, and 

oxide of iron, but only a very little fine secondary quartz. (Slide 1224.)

6. South.side Campement d'Ours Island, Lake Huron. (Logan's "3 f," 

" Upper Slate Conglomerate.")

A feldspathic quartzite, the feldspars including both orthoclase and oligoclase, but 

not nearly so plenty as in the rock last described. The quartz fragments are very 

much enlarged, so as to interlock intricately. The lines of division betwe'en the enlargements and the original fragments are only rarely satisfactorily seen, some sections being quite without them. That the interlocking quartz areas of this rock are 

due to enlargement of quartz fragments would never be suspected but for'their previous discovery in other similar rocks and in other parts of this same layer. Only a 

very small quantity of the interstitial quartz in this rock appears to have crystallized independently of the original fragments. (Slide 1226.)

A number of rocks on the west and south sides of Campement d'Ours, belonging 

with the same member of the series as the above, were examined, and all showed essentially the features above noted. ' 

7. North shore of Lake Huron, two iniles east of McClennan's Landing. 

(Logan's " 3 f," " Upper Slate Conglomerate.")

A purple, vitreous, non-feldspathic quartzite, composed chiefly of rounded quartz 

grains, which have rarely, if evef, received any enlargement, and consequently do 

not. interlock. Interstitially finely-divided secondary silica has been deposited, in 

part in an amorphous form. There is also a good deal of kaolinic material in the interstices. The presence of this material and also of a small quantity of iron oxide 

and the absence of enlargements give the sections of this rock just the appearance 

of those of an ordinary sandstone. Nevertheless it is much indurated, and the indu- 

' ration is plainly due to the independent secondary deposition of interstitial silica. 

(Slide 1233.)

8. McClennau's Landing, north shore of Lake Huron. (Logan's "3 g," 

" Bed Quartzite.")

A light-red, non-feldspathic quartzite. This rock is a good'deal like the last described, the induration being mainly due to the independently oriented interstitial 

silica, but the quartz fragments are, for the most part, somewhat enlarged. (Slide 

1238.)

9. Two miles west of McClennan's Landing, north shore of Lake Huron. 

(Logan's U 3 k," "Bed Jasper Conglomerate.")

A white quartzite, made up chiefly of quite large quartz grains, all of which are 

more or less enlarged, though the bounding lines of the original fragments are only 

here and there perceptible. There is, however, not much interlocking of the quartz 

enlargements, there being a good deal of interstitial material in the shape of kaolin, 

muscovite scales, and finely-divided quartz. (Slide 1239.)

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THIN SECTIONS OF SANDSTONE AND QUARTZITE.
IKVINOANDVANHIBE.J ENLARGEMENTS IN HURONIAN EOCKS. 25

10. Near the mouth of Echo Eiver, Canada side of Lake George, Saint 

Mary's Eiver. (Logan's "3 h," "Eed Jasper Conglomerate.")

A conglomeratic quartzite composed chiefly of clear,quartz pebbles, one-fourth to 

one-half inch in length, with rarer ones of red jasper. These are imbedded in a fine, 

much-indurated matrix, apparently composed of the same materials. Under the 

microscope the matrix is seen to be composed of finely-divided, perhaps sometimes 

amorphous silica, with kaolinic material and oxide of iron. The quartz fragments 

are enlarged, but never so much as to interlock with one another, and the outlines 

of the original grains are often imperceptible. Some of the large quartz areas appear 

to fade away into the fine matrix in the manner described on a previous page. This 

appearance is plainly due to the fact that, as the enlargement of the grain progressed, 

it became more and more difficult to thrust aside the clayey matrix, more and more 

of which was consequently included within the enlargements, more and more of the 

secondary silica at the same time departing from its allegiance to the original grain 

and depositing independently. (Slide 1242.)

11. North shore of St. Joseph's Island, Lake Huron. (Logan's "3 i," 

"White Quartzite.")

A gray, non-feldspathic quartzite. The induration is principally due to the enlargements of the original grains, which sometimes interlock closely, but in places 

there is a good deal of a fragmental matrix of kaolinic material, including muscovite scales, in which cases the grains sometimes appear to fade away into the matrix, 

as described in the preceding. The outlines of the original grains-are often quite distinctly seen. (Slide 1228.)

12. East tfeebish Island, St. Mary's Eiver. (Logan's " 3 i," " White 

Quartzite.")

A light gray to white quartzite. At times completely vitrified and without any 

trace of a fragmeutal appearance, but in other places a loose sandstone, with crystal 

faceted grains, there being every possible phase between those two extremes. In 

the thin section, the most completely vitreous kinds are found to be made up wholly 

of enlarged quartz fragments, there being none of the independently deposited interstitial silica or of any other interstitial material. The quartz areas interlock intricately, the outlines of the original fragments being everywhere strongly marked. 

In sections of the less completely vitreous kinds, a fine interstitial silica is to be seen 

in greater or less quantity. Some of the quartz fragments present the appearance, 

of graduation into the matrix, due to the gradual change in the depositing silica from 

dependence upon .the original fragments to independence of them. Fig. 2, Plate V, 

is drawn from the East Neebish quartzite. The arenaceous varieties of the East Neebish rock are noted below in another connection. (Slides 1019 to 1024, inclusive.)

13. Eocky islets in Saint Mary's Eiver, northwest of Saint Joseph's 

Island, Lake Huron. (Logan's " 3 i," " White Quartzite.")

These islands show a gray quartzite similar to that of Neebish Island. (Slides 1025, 

1028.)

14. McDonald Township, six miles east of Saint Mary's Eiver, Canada. 

(Logan's " 3 i," " White Quartzite.")

A white, completely vitreous quartzite, entirely similar to the most vitreous phase 

of the Neebish quartzite. The outlines of the original fragments are everywhere 

very plain in this section. (Slide 1240.)

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26 SECONDARY ENLAEGEMENTS OF MINEEAL FRAGMENTS. [BULL. 8.

15. From near the mouth of Echo Eiver, Canada side of Lake George, 

Saint Mary's Eiver. (Logan's « 3 i," « White Quartzite.")

A completely vitreous quartzite, similar to that of Neebish Island, except in having 

a very small quantity of intrestitial kaolinic material. (Slides 1245, 1246.)

B. Schistose quartzites.

16. Islands two miles southeast of Neebish Eapids, Saint Mary's Eiver. 

(Logan's " 3 i," " WKite Quartzite.")

Light-gray, argillaceous, schistose quartzites, differing from the non-schistose quartz - 

ites above described in containing a very large amount of a clayey matrix, and in 

the schistose structure. The rather unusually large quartz fragments are "wholly 

separated from one another by the matrix, and, as is generally the case when there 

is much of a clayey matrix, the enlargements are but slight. Some of the quartz 

fragments are complex, and'appear to have received complex enlargements. '(Slide 

1031.)

C. Sandstones.

17. East Neebish Island, Saint Mary's Eiver. (Logan's " 3 i," " White 

Quartzite.")

Intercalated in and grading into the vitreous quartzite above described (No. 12) is 

a reddish, very coarse-grained, feebly indurated sandstone, each one of the grains 

being furnished with crystal faces from secondary enlargement. The crystal faces 

are in this case very much larger than in any other case that we have yet noted. 

Some of the grains, each a single quartz individual, reach 'as much as one-fourth inch 

in diameter, and have crystal faces of correspondingly large size, while half the mass 

of the rock is composed of grains which exceed one-sixteenth inch in diameter. Occasionally some of these grains are complex, but most of them are single individuals. 

The oxide of iron cement is very abundant, and the secondary enlargements of the 

grains have always between them and the original surfaces a heavy border of the 

iron oxide. Fig. 2, Plate II, represents one of these grains broken by hand from the 

rock, as seen in a balsam mounting enlarged 67 diameters. The crystal facets bounding the grain are not seen on this mounting, but only thorough, iron-stained surface of

the original grain and the outlines of the pellucid enlargement. Fig. 1 of the same

plate shows the positions of the crystal faces upon another grain, the positions of the 

faces having first been drawn in with the camera from a dry mounting, after which, 

without altering its position, the fragment was covered with balsam, and the kernel 

drawn in its position within the crystal. The very slight coherence of this rock as 

compared with the completely vitreous quartzite into which itx grades within a few 

inches, is plainly to be attributed to the relatively coarse character of this rock, and 

to the supply of indurating quartz not having here been sufficient to fill out the largesized interstices, and its having consequently developed crystalline faces. (Slide 1391.)

D.^Graywackes.

18. Palladreau Islands, north shore Lake Huron. (Logan's "3 d," 

"Lower Slate Conglomerate.")

A very dark greenish-gray, nearly black, fine-grained, compact rock, having an 

aphanitic matrix, in which are scattered minute particles of quartz and feldspar. 

Except for very sparsely scattered" granite and porphyry pebbles, the appearance is 

more that of a very fine-grained porphyritic green-stone than that of a clastic rock. 

The clastic nature is, however, very evident in the thin section, which shows a 

ground-mass composed very largely of kaolin and chlorite, mingled with fine particles of feldspar and quartz, with more or less brown oxide of iron and magnetite.

(210)
VAN HISE.] ENLARGEMENTS IN HURONIAN ROCKS; 27

The kaolin and chlorite are evidently the results of the alteration of the feldspathic 

portion of the matrix. Thickly scattered through this matrix are larger fragments 

of quartz and feldspar, between' which and the particles of the matrix there is every 

gradation in size. The feldspars include both plagioclase and orthoclase. The 

rounded quartz fragments here and there show narrow enlargements, and also the 

gradual fading away into the matrix which is characteristic of rocks where there is 

much of a finely fragmental matrix. It is possible that some of the induration has 

been produced by the independent secondary deposition of fine silica, but it seems 

to be largely due in this case to the chloritic alteration of the matrix. (Slide 1032.)

19. From tbe mainland, four to five miles east of Oampement d'Ours Island Lake-Hurou. (Logan's " 3 f," " Upper Slate Conglomerate.")

The specimens collected from the "Upper Slate Conglomerate," as exposed along the 

north shore of Lake Huron, between the French Islands and Campement d'Ours, are 

chiefly of rocks nearly allied to the last described, though including also some true 

vitreous quartzites, some of which have been above alluded to, and between* which

and the predominating graywackes there is a complete gradation. A part of the

rock is very highly conglomeratic, with pebbles of granite, felsitic porphyry, and 

jasper, but in other portions the pebbles are wanting, or are very sparse and small. 

These present a great variation in coarseness, the finest kinds being contorted clayslates, but they are all composed of essentially the same materials as noted in the 

slate conglomerate from the'Palladreau Islands above described, like which they are 

all dark colored, from the presence of much chlorite. Enlargements of-the quartz 

fragments are generally to be made out, and, at least in those kinds which are more 

distinctly quartzitic, much of the induration is due to these enlargements. Induration 

seems also to have been produced by the deposition of a fine interstitial quartz, and 

a chalcedo'nic or amorphous silica.' The feldspar grains, including both orthoclase 

and plagioclase, also often present an appearance which suggests that they too have 

been enlarged by second growths. Sharp lines of division between the supposed 

enlargements and the original nuclei, as seen so often in the. case of enlarged quartz 

fragments, we did not satisfactorily make out; but in many instances the outer portion of the grain is relatively undecomposed and free from inclusions, as compared 

with the nuclei. This appearance, taken together with the fact that secondary enlargements of feldspar fragments have been proved to occur in certain Keweenawau 

sandstones, lead us to believe that we have them here also. 17 All of these rocks 

carry a very large amount of a green chloritic mineral, which has plainly been produced from the feldspars by a metasomatic process. ,

These graywackes are all typically " recomposed." rocks, and while plainly fragmental, are no more so than many kinds that are classed as crystalline schists. The 

enlargement of the quartz and feldspar grains, the production of abundant chlorite, 

the presence of much feldspar, and the secondary deposition of an interstitial silica 

certainly would have to be carried but little further to give us a rock in which it 

would be exceedingly difficult to detect the presence of the detrital material. (Slides 

1215 to 1218.)

IN THE IRON-BEABING SEBIES OP MABQVETTE, MICH.

A. Vitreous quartzites.

20. Quartzite range, south of Marquette, near shore of Lake Superior, 

(K.W. J, Sec. 6, T. 47, E. 24 W., Michigan). (Brooks's u Formation 

V," "Lower Quartzite;")

A bright-red vitreous quartzite, composed almost wholly of interlocking areas of 

quartz, which are all taken to have been produced by the enlargement of fragmental

17 See Part II of this bulletin ; also American Journal Science, May, 1884, p. 399.

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28 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

nuclei, since in a number of them the outlines of these nuclei are plainly recognizable. The red color of the rock is due to the presence of a small quantity of red oxide of iron. (Slide 1009.)

21. Shore of Lake Superior, two and a half miles southeast of Marquette, 

(SE. J,Sec. 36, T. 48, E. 25 W., Michigan). (Brooks's "Formation 

V," " Lower Quartzite." 18 )

This is the locality of the unconfprmable contact of the Lake Superior sandstone 

and Huronian quartzite, made classical by Foster and Whitney. A white, strongly 

vitreous quartzite. The induration appears to be almost wholly due to the interstitial deposition of fine quartz, the original outlines of the quartz fragments coinciding 

for the most part with the outlines as now seen of the individual areas. There is a 

little kaolinic interstitial material. (Slide 1013.)

22. Gannister quarries, north and south sides of Carp Eiver, near Marquette (Sees. 35 and 36, T. 48, E. 25 W., Michigan.) (Brooks's 

" Formation V," u Lower Quartzite.")

Light-gray, highly translucent, completely vitrified quartzites. These rocks are 

composed almost wholly of quartz, there being a very minute quantity in some of the interstices.of kaolinic material. Although coming from the same vicinity and layer as 

the rock last described, and not differing very much from it microscopically, we have 

in these rocks a case where the induration and vitrification are wholly due to secondary enlargement of the original fragments. The outlines of the nucleal grains are 

usually very distinct, and the enlargements interlock quite intricately, so that, as seen 

in the polarized light, this rock seems to be completely made up of originally deposited areas of quartz. In some portions the layers of the gannister quarries are quite 

thin-bedded. In sections from some of these thin-bedded portions in the quarries on 

the north side of Carp River the quartz areas are all elongated in a common direction, 

the lengths of the areas being usually great in proportion to their widths. These 

elongated grains of quartz interlock and oyerlap one another just as do the quartzes 

of many mica schists and gneisses. This arrangement in the present case is perhaps 

partly due to the pressing into this position of originally oblong areas, but it seems 

also to be duo in part to the elongation of the quartzes by secondary enlargements'. 

Fig. 1, Plate VI, represents a thin section of tine non-schistose portion of this rock.

(Slides 1012, 1479.)

23. Northwest corner of Teal Lake, Michigan.' (Brooks's "Formation

V," "Lower Quartzite." )

, A gray and brown vitreous quartzite. The same ledge shows also greenish, chloritic quartz-schists. In the sections of the non-schistose portions the induration is 

seen plainly to be the result of the interlocking of the enlargements of the original 

clastic particles, whose smoothly-rounded outlines are strongly marked. The cementing silica has, however, not all of it united with the original grains, some of it having separated out interstitially in minute interlocking areas. The peculiar appearance of gradation of a quartz area into fine interstitial quartz, due to the diminution 

outwards in power of the crystalline influence of the nucleal grain, is here noticed 

also. The more schistose portions of the rock of this ledge are seen in the thin section 

to carry a larger proportion of kaolin, and .to have but little of the indurating silica 

co-ordinated with the original fragments, most of it having been deposited independently of them. (Slide 988.)

18 Geol. Sur. of Mich., Vol. I, p. 83. 

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U.S. GEOLOGICAL SURVEY

THIN SECTIONS OF QLJARTZITES.
ENLAKGEMENTS IN HUKONIAN ROCKS. 29

24. Hanging wall of Palmer Mine, Michigan. (Brooks's " Formation V," 

" Lower Quartzite.")

A dark-gray, conglomeratic quartzite. The numerous, large-sized quartz fragments 

of this rock, some of them simple, some of them complex, are buried in an abundant 

matrix, which is composed of finely-divided quartz mingled with amorphous or chalcedonic silica, the latter at times predominating, along with kaolinic material, flakes 

of muscovite and chlorite, and of oxide of iron. The quartz fragments are often 

angular, but there is no evidence that the angularity is due to secondary enlargements qf rounded, grains. The induration seems to be wholly due to the independently deposited interstitial silica. (Slide 973.)

25. Hanging wall, Saginaw Mine, Negaunee District, Michigan. 

(Brooks's " Formation XIV," " Upper Quartzite.")

A Very dark-colored, conglomeratic quartzite, the pebbles partly of clear quartz and 

partly of red and black jaspery or cherty material. The rock is very much indurated, 

the induration being chiefly due to the independent deposition of interstitial quartz 

and of some amorphous Silica, there being but few and small enlargements of the 

quartz fragments. Oxide of iron is very abundant in the matrix, which includes also 

some kaolinic material and muscovite scales. (Slide 1457.)

26. Hanging wall, Spurr Mine, Michigamme District, Michigan. 

(Brooks's "Formation XIV," "Upper Quartzite.")

A highly vitreous, dark-gray, conglomeratic quartzite, mostly made, up of large, 

clear, often interlocking quartz areas, which are in many cases plainly, and inferentially always, due to the enlargement of fragments. A few biotite flakes, often altered 

into chlorite, as also particles ofjnuscovito, microcline, and orthoclase, are contained. 

Within six feet across the strike this clear, vitreous quartzite passes into the chlorite schist, which carries the well-known chlorite pseudoinorphs after garnet. There 

is a complete variation from one rock to the other within this distance. (Slide 1279.)

B. Quartz-schists.

27. Quartzite range, south of Marquette, near shore of Lake Superior 

(N. W. J, Sec. 1, T. 47, E. 24 W., Michigan). (Brooks's "Formation V," " Lower Quartzite.")

A red, dolomitic quartz-schist. This rock grades within a few feet into the red, 

non-schistose quartzite described above as No. 20, and in another direction, within 

.an equally short distance, into a clay slate, with strong transverse cleavage. The 

thin section shows quartz grains imbedded in a fine matrix. The quartz grains often 

show strongly marked secondary enlargements. The matrix contains some little kaolinic matter and some fine quartz, but appears to be chiefly made up of a finely crystalline dolomite, which is to be regarded as of a secondary nature. The red color is 

due to a minute quantity of iron1 oxide. (Slide 1007.)

28. North of Michigamme Mine (N.W. 4, K W. 4, Sec. 20, T. 48, E. 30 

W., Michigan). (Brooks's " Formation V," " Lower Quartzite.")

A dark- and light-banded quartz-schist, the light-colored bands being vitreous and 

quartzitic, the dark-colored ones being much finer and more clay-slate-like. There 

is a tendency to transverse cleavage, especially in the dark-colored bands. In the thin 

section the light-colored bands are seen to be composed mainly of worn grains of 

quartz, which have often been enlarged, and sometimes so much so as to interlock 

quite deeply. An interstitial material is present, composed of very fine quartz, with

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30 SECONDARY ENLARGEMENTS OP MINERAL FRAGMENTS. [BULL. 8.

biotite and kaolin scales, with a little chlorite and' iron oxide. In sections of the 

'da*k-colored bands this matrix material becomes predominant. (Slides 1284,1285, 

1286.)

0. Mica-schists.

29. North of Michigarmne Mine (N. W. £, K W. J, Sec. 20, T. 48, E. 30 W. 

Michigan). (Brooks's "Formation V," "Lower Quartzite.")

A very fine-grained schist, strongly marked with very thin bands of sedimentary 

deposition, and exhibiting an imperfect slaty cleavage. Closely resembles much of 

the slate exposed along the Saint Louis and Mississippi Rivers, Minnesota, and grades 

into the rock last described, the only difference being that here the finer material 

predominates. In the thin section this resemblance is borne out, and the rock is seen 

to be composed as the matrix of No. 28. Some of the minute quartzes have distinctly 

been enlarged from fragmental particles. Crystals of garnet occur very sparsely 

scattered through the section. Ifc is difficult to say how much of the fine quartz of 

this rock is the result of crystallization in situ, and how far the result of the enlargement of fragments. (Slide 1289.)

D. Sandstone.

30. Short distance north of the foot-wall of Spurr Mine, Michigamme, 

District, Michigan. (Brooks's "Formation XII.")

A fine-grained, saccliaroidal, very friable, white sandstone, the grains being provided with crystal faces. Certain bands, one-eighth to one-fourth of an inch wide, 

carry much magnetite. The sand crumbled from the rock by hand shows, in a balsam mounting, that each one of the faceted grains has a rounded fragment as a 

nucleus. It is only with a particular disposition of the light that the outlines of the 

original grains can be detected, so clear are both the nuclei and the enlargements. 

The crystal terminations are generally both present. See Fig. 3, Plate II. (Slides 

1274,1433, 1434.)

FROM THE IRON-BEARING SERIES OP THE PENOKEE REGION, WISCONSIN.

A. Vitreous guartzltes. 

i

31. Near Penokee Gap, Ashland County, (N. W. |, Sec. 14, T. 44, E. 3 

W., Wisconsin.) (" Formation III" of the Penokee series, " Siliceous Schist.") 19

A greenish, vitreous quartzite, composed almost wholly of intricately interlocking 

quartz areas of some size, each one of which has; however, plainly been enlarged 

from a fragmental nucleus. Chlorite in small particles forms the only other ingredient. (Slide 1402.)

32. Gorge of Tyler's Fork, Ashland County (S.E. J, N.E. |, Sec. 33, T. 45, 

E. 1 W., Wisconsin). ("Formation III.")

A greenish, vitreous quartzite, closely like the rock last described, except that the 

induration, though chiefly, is not wholly due to the enlargement of the original fragments, there being present quite a quantity of a finely divided interstitial quartz. 

The chlorite, besides occurring in bunches, is noticed also to occur in films around 

the outlines of the nucleal grains of the quartz areas. (Slide 2094, Wisconsin survey 

series.)

19 For the stratigraphy of the Penokee series, and the numbers given to its subordinate members by R. D. Irviug, see Geol. of Wis., Vol. Ill, p. 104. For a description of Formation III throughout its extent, see the same, pp. 111-118.

(214)
ENLARGEMENTS IN HUKONIAN ROCKS. 31

33. Bad Eiver, Ashland County (S.W. £, KW. £, .Sec. 11, T. 44, E. 3 W., 

Wisconsin). ("Formation XV." 20 )

A very dark-gray feldspathic quartzite, composed of angular quartz and partly 

kaolinized feldspar fragments (the former often slightly enlarged) imbedded in an 

.abundant matrix composed largely of the same materials, with a good deal of a blackish iron oxide in fine particles. As is usual where there is much of a fine fragmental 

or clayey matrix, the quartz fragments appear to merge into the matrix. (Slide 1496, 

Wis. sur. series.) .

34. Near Penokee Gap (west line KW. J, Sec. 11, T. 44, E. 3 W., Wisconsin). (" Formation XIX." 21 )

A very fine-grained, dense, black, vitreous quartzite. Quartz in minute' particles 

is the most abundant ingredient. Much of it appears clearly to be of a clastic origin, 

and the grains have often received secondary enlargements. Biotite in abundant, 

minute, brown scales; fragments of feldspar, pyrite, and brown iron oxide are the remaining ingredients. (Slide 1113.)

B. Quartz-schists.

35. The gorge of Tyler's Fork, Ashland County (KB. £, Sec. 33, T. 45, 

E. 1 W., Wisconsin). (" Formation III.")

A greenish-gray, vitreous quartzite, very clearly resembling No. 28 of this list. 

Quartz, in relatively large, interlocking areas, composes fully three-fourths of the 

section, each area having a distinctly marked, nucleal fragment. The enlargements 

of these fragments are often unusually wide, and the interlocking at times quite intricate. A little, finely-divided quartz is present in the interstices. Chlorite occurs 

in large rounded areas, which are taken to have resulted from the decomposition of 

feldspar fragments in films and patches between the quartz areas, and in films.followiug the outlines of the original grains, thus taking the place more usually occupied 

by iron oxide, which is, however, also present'to some extent here. (Slide. 1111.)

36. South line Sec. 27, T. 45, E. 2 W., Ashland County, Wisconsin, 

(" Formation XXI." 22)

A light-gray, fine-grained quartz-schist. Rather sparsely scattered fragments of 

quartz and feldspar, the former the most abundant, are scattered through a matrix 

composed of the same materials, with more or less kaolin, muscovite, chlorite, and 

iron oxide, in fine particles. The quartz fragments are often distinctly enlarged. 

(Slide 1113.)

C. Mica-schist.

37. West line S.W. £, Sec. 2, T. 44, E. 3 W., Ashland County, Wisconsin. ("Formation XXI," the great mica-schist at.the top of the 

series.)

A light-gray, very fine-grained, quartzose mica-schist. Quartz in closely fitting 

areas, in many of which a nucleal fragment may be recognized, is the chief constituent. There is also some fragmental orthoclase. The mica (biotite) lies between the 

quartz areas, and along with it there is often some brown oxide of iron. (Slide 2006, 

Wis. sur. series.) .. ' -r 

20 Geol. Wis., Vol. Ill, p. 142. 

21 Geol.Wis.,Vol.III,p,144. 

» Geol. Wis., VoL'in, pp. 145-149.

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32 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

D. Graywaclce and graywacke-slate.

38. Tyler's Fork (ff.E. J, Sec. 28, T. 45, E. 1W., Ashland County, Wisconsin). (" FormationXVII." 23> 

A very dark-gray, fine-grained rock, similar macroscopically and microscopically 

to No. 33 of this list, differing only in the larger proportion of the feldspathic and 

clayey material. Many of the quartz grains are distinctly enlarged, and present the 

common appearance of merging into the matrix. The decomposed feldspar fragments 

have abdut them often borders of a fresh feldspathic material, an occurrence suggesting tha,t they too have received secondary enlargements. (Slide 2104, Wis. eur. series.)

E. Arenaceous quartzite and sandstone.

39. Penokee Gap, Ashland County, Wisconsin, (KB. |, KW. £, Sec. 14, 

T. 44, E. 3 W., Wisconsin). (" Formation II."24)

A inilky-white, arenaceous or semi-vitrified quartzite. Except some few minute 

particles of brown oxide of iron, the slide shows nothing but quartz in closely fitting, 

sometimes interlocking areas, within many of which may be seen the outlines of the 

nucleal fragments. The slide is evidently from one of the more vitrified portions, the 

rock being quite irregular dn the degree of induration. (Slide 1110.)

40. Mount Whittlesey, Ashland County (KW. £, KW. £, Sec. 16, T. 44, 

E. 2 W., Wisconsin). (" Formation II."-)

A very fine-grained, white, indurated sandstone, closely like the last rock described, 

except that the enlargements of the grains are very frequently furnished with crystal 

faces, as may be seen both in the thin section and in the balsam mounting of sand 

crumbled from the rock. This is evidently a common peculiarity of this layer in the 

Penokee series, since hand specimens from different localites are made up of sparkling grains. There is often a very abrupt transition from the highly arenaceous to 

the strongly vitrified phase. (Slides 1406,1465,1482.)

IN THE SLATES OF THE SAINT LOUIS RIVER, MINNESOTA.

41. Knife Falls, Saint Louis Eiver, Minnesota.

A fine-grained, light-gray, highly argillaceous schist. _ Minute fragments of quartz, 

orthoclase, and oligoclase, the first-named often with small enlargements, are buried 

in a fine matrix, composed partly of the same materials and partly of kaolin,- with 

some chlorite. 

42. Near Mahtowah, Minnesota.

An arenaceous schist, closely resembling the last described, both macroscopically 

and microscopically, except that it is somewhat coarser grained. The quartz fragments 

are often enlarged. (Slide 766.)

43. Saint Louis Eiver, near Thompson, Minnesota.

A very dark-gray, fine-grained graywacke. The thin section shows the rock to be 

composed much like the last two described, except in containing a larger quantity of 

feldspar fragments, and in having a larger proportion of chlorite in the matrix. The 

quartz fragments are often distinctly enlarged.

These rocks are all somewhat nearly allied to the gray wacke-slates of Lake Huron. 

They are, however, whilst fine-grained, only the coarser phases of the great slate formation in which they occur, the predominating phases of which are true-clay slates

. ' ' 23 Geol. Wis., Vol. Ill, p. 142. . 

. ' . M Gcol. Wis., Vol. in, p. 108.

(216)
IKYING AND VAN HiBE.j ENLARGEMENTS IN HURONIAN ROCKS. 33

and a very fine-grained, shining mica-slate, in which the proportion of decomposed 

feldspar detritus is often very large, and the quartz fragments are so minute that if 

any secondary enlargements occur they are very difficult of detection. The whole 

series is affected by a very strong transverse cleavage, the fine bands of sedimentary 

lamination being at the same time often most beautifully preserved. (Slide 761.)

IN THE QVART/ITE FORMATION OP THE BABABOO REGION OP WISCONSIN.

A.' Vitreous quartzites.

44. Caledonia, Columbia County, Wisconsin. '

A grayish-white quartzite conglomerate, the pebbles being of white quartz and of 

small size. In the thin section quartz fragments of some size, often showing distinctly 

secondary enlargements, are buried in a finer matrix, chiefly of the same material, 

some of which may be fragmental, but much of which appears to be originally deposited material. (Slide 729.)

45. Upper Narrows of the Baraboo Eiver, Sauk County, Wisconsin.

Dark purple, vitreous, close-granular quartzite, made up almost wholly of interlocking areas of quartz, each one of which has been produced by the enlargement of 

a fragmental nucleus whose outline is always strongly marked by oxide of iron. 

The lines along which the interlocking areas of quartz join are peculiarly jagged. 

There is also present some of a fine, independently deposited interstitial quartz. (Slide 

745.)

46. Freedom, Sauk County, Wisconsin.

A pinkish white, very close-grained, vitreous, translucent quartzite. The thin section is made up entirely of irregularly outlined, interlocking, angular areas of quartz, 

all of which have evidently been formed by the enlargement of fragmental nuclei, the 

outlines of which, however, are usually very faintly marked. While plainly composed in the main of detrital material, this rock, but for the discovery that these enlargements exist in other quartzites, would undoubtedly be taken as made up entirely 

of quartz crystallized in situ. (Slide 744.)

47. Westfield, Sauk County, Wisconsin.

A pinkish, vitreous, translucent quartzite, composed chiefly of interlocking quartz 

areas, the outlines of the original fragments being, generally very distinctly marked. 

The enlargements are usually not broad. There is a small quantity of fine interstitial quartz which appears to have been deposited in situ.

B. Quartz-schists.

48. Lower Narrows of the Baraboo Eiver, Sauk County, Wisconsin.

A yellowish-white, granular, argillaceous quartz-schist, composed in about equal 

proportions of a fine clayey matrix, and of rounded fragments of quartz with some of 

feldspar. The matrix includes also >some fine quartz. The quartz fragments show 

the usual small enlargements and appearance of fading into the matrix, so often noted 

above as characteristic of clayey quartzites. (Slide 735.)

49. Ableinan's, Sauk County, Wisconsin.

A dark-grayish, vitreous quartz-schist, made up chiefly of enlarged quartz grains, 

elongated in a common direction, whence the schistose structure. There is a minor 

quantity of fine interstitial quartz. (Slide 748.)

50. Upper Narrows of the Baraboo Eiver, Sauk County, Wisconsin.

Pink, fine-grained, quartz-schist, made up chiefly of grains of quartz, with their 

longer axes lying in a common direction, each enlarged from a nucleal fragment.

(217). 

Bull. 8-^-3
34 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS

One-fourth of the rock is made up of a fine filling material, which is about equal parts 

of fine quartz and kaolin. (Slide 746.)

C. Sandstone. 

51. Devil's Lake, Sank County, Wisconsin.

The larger portion of the quartzite in the Devil's Lake region is without arenaceous 

appearance, but now and then a tendency to an arenaceous appearance is notable, 

and occasionally small areas are met withvrhere the rock is only a slightly indurated 

or even a quite loose sandstone. The transition from friable sandstone to the most 

indurated quartzite is quite abrupt. The present slides consist of a balsam mounting 

pulverized from one of the slightly indurated portions. Each rolled grain of sand is 

seen to be surrounded by a secondary border of limpid quartz, on which, however, 

crystal faces are not to be observed, the interference having been too great. (Slides 

820,821.)

IN THE QUARTZITE FORMATION OP SOUTHERN MINNESOTA.

A. Vitreous quartzites. 

52. Bedstone, Nicollet County, Minnesota.

In southwestern Minnesota, and westward in Southeastern Dakota, as far as the 

James River Valley, are areas of a sandstone and quartzite formation, which evidently 

underlies all of this region, the exposures being detached from one another by the 

overlying Cretaceous and Quaternary formations. Unfortunately, the next newer 

formation with which it is seen in contact is the Cretaceous, so that stratigraphical 

proofs of its geological position are wanting. It is contrasted so completely with the 

Potsdam formation of the Mississippi Valley that there can be no question of its in. 

ferior position. So far all who have examined it of late years are agreed. Professor 

Winchell, if he is rightly understood by us, is disposed to regard it as the equivalent 

of the lower portion of the copper-bearing series. Certain of the reddish, more argillaceous, and more sandy parts of the formation are often much like some of the 

red sandstones of the copper series, although the similarity does not hold on closer 

inspection. In its quartzitic portions the formation is almost identical in character 

with the Huronian quartzites of the Baraboo region of Wisconsin. In its more argillaceous portions, also, it approaches, very nearly the argillaceous members of the series 

of the Penokee region, and thepipestone-bearing quartzites of Barron County, Wisconsin. These resemblances, the evident considerable thickness of the series, and the 

differences between it and the Keweenawan rocks leave little doubt in our minds of 

the correctness of the position taken by those who would refer. it to the Huronian. 

It may be said that much of the quartzite of this region is near to much of the 

quartzite of the Huronian of Lake Huron.

At Redstone the transitions from argillaceous, reddish sandstone to completely 

vitrified, brick-red to purple quartzite, and from these again to completely loose sandstones, are frequent and abrupt. In places, over considerable areas, the appearance 

is as if the rock at higher levels had been vitrified by exposure. But in the railway 

cutting it is seen that the vitreous quartzites are not restricted to the exposed portions, but are interstratified with, and arranged in irregular areas in, an entirely unindurated crumbling sandstone. The peculiarly irregular distribution of the induration, and the abrupt transitions from indurated to non-indurated material, suggest 

the possibility of its production by the descent along joints and the spreading thence 

through the layers of a silica-bearing solution. The thin sections of the completely 

vitrified quartzites of this place show the outlines of the original fragmental grains, 

strongly marked by borders of oxide of iron. In the main the fragments are simple, 

but at times they are composed each of several interlocking quartz areas. All of

(218)
IKYING AND VAN HisE. I ENLARGEMENTS IN ANIMIKIE EOCKS. 35

these fragments have been enlarged, the simple ones in' the usual mariner and the 

complex ones into larger complex areas. The enlargements at times interlock, but in 

other portions of the sections interstices are left between them, which have been filled 

by an independently deposited silica, a portion of which is chalcedonic or amorphous. 

(Slide 1376.)

53. Near JSTew Ulm, Mcollet County, Minnesota.

A fine conglomerate, forming the matrix of a boulder conglomerate composed of 

white quartz pebbles, imbedded in a still finer matrix of fine quartz, kaolin, and oxide 

of iron. The quartz fragments were in the main originally complex, but have been 

slightly enlarged. (Slide 1373.)

54. Delton, Cottonwood County, Minnesota.

A pinkish, glassy quartzite. The thin sections show essentially the same characters 

as No. 52 of this list. Some of the interstitial material of these rocks is fibrous, chalcedonic silica arranged radially about some of the complex grains of quartz. (Slides 

1380,1381.1382.)

55. Mound Creek, Germantown, Cottonwood County, Minnesota.

An arenaceous, gray quartzite. The thin sections resemble those of the immediately 

preceding numbers, except that the induration has not proceeded so far, the enlargements of the grains not having commonly interlocked. There is much of a fine quartzose matrix. (Slide 1383.)

B. Sandstone.

56. Bedstone, Mcollet County, Minnesota.

A fine-grained, somewhat indurated, red, argillaceous sandstone. Fragments of 

quartz, partly simple, partly finely complex, the former often enlarged, are buried in 

a matrix of red iron oxide, clayey material and fine quartz. (Slide 1375.)

57. Bedstone, Nicollet County, Minnesota.

One end of the specimen is a purple vitreous quartzite, like No. 52; the other a loose 

sandstone, with the grains faceted from secondary enlargement. We have, then, in 

this specimen the two extremes of the process of induration. (Slides 1377,1378.)

IN THE ANIMIKIE SERIES OP NORTHERN MINNESOTA AND THE THUNDER BAT REGION OP

LAKE SUPERIOR.

A. Vitreous quartzites.

58. Prairie Eiver Falls, (Sec. 34, T. 56, B. 25 W., Minnesota).

A red, vitreous quartzite, closely resembling much of the red quartzite of Southern 

Minnesota (e. g., No. 54 of this list); also the red quartzites occurring in the Marquette (e. g., No. 20) and Baraboo Huronian regions (e. g., No. 47). The induration has 

been entirely produced by the enlargement of very much rounded fragments, whose 

outlines are beautifully marked in the thin section by lines of red and brown oxide 

of iron. The enlargements have often very intricately interlocked. Eutile needles 

are plentiful in the original fragments, coming up often quite to their outlines, but 

are altogether absent from the enlargements. There is no other mineral of importance 

present. The quartz fragments are usually simple, but are occasionally made up of 

two or more interlocking quartz areas. Figs. 1 and 2, Plate IV, magnified 39 diameters, represent portions of this rock in the ordinary and polarized lights, so that the 

present and original extents of the quartz areas may be readily seen. See also Fig. 2, 

Plate VI., upper half. (Slides 1088, 1089.)

(219)
36 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS., [BULL.8.

59. Wauswaugoning Bay, Lake Superior, Minnesota.

A light-gray, vitreous quartzite. Angular quartz areas, each plainly enlarged from 

a nucleal grain, and often interlocking, make up most of the rock. There are also 

present fragments of feldspar and fragments made up of very minute interlocking 

quartz areas. Chlorite is present in the matrix, which appears to be in part composed of quartz deposited in titu. (Slide 413.)

60. Pigeon Point, Lake Superior, Minnesota.

A very dark-gray, nearly black, compact, very fine-grained, vitreous quartzite. 

Consists of angular quartz areas, plainly enlarged from fragmental nuclei, whose outlines are often visible, with some fragments of feldspar (both orthoclase and plagioclase), imbedded in a matrix made up of minute interlocking quartz areas, chlorite 

and biotite flakes and abundant small round grains of a brightly polarizing, colorless 

mineral, which is nearer in appearance to the sahlite variety of angite than to anything else with which we are familiar. This rock is very near to those described as 

vitreous graywackes, the only diiference being in its greater richness in quartz, and 

highly vitreous character. It is also very close, indeed, to the more quartzitic phases 

of the "slate-conglomerates" of Lake Huron, and is quite as completely a "crystalline" rock as anything except the greenstones to be found in the type Huronian of 

Lake Huron. It is a type of rock which is largely concerned in the make-up of the 

Auimikio series. It is directly interstratificd with arenaceous quartzites or even 

sandstones. (Slide 423.)

B. Arenaceous quartzites.

61. Portage Bay Island, Minnesota, coast of Lake Superior.

The light-gray, fine-grained arenaceous rock of Portage Bay Island is often little 

more than a slightly indurated sandstone, but in places it becomes a decided quartzite, 

and though always somewhat more arenaceous, gives sections which resemble very 

closely those of No. 59 of this list, the induration being merely not quite so strong. 

The outlines of the original fragments are beautifully distinct, and the enlargements 

are very broad. There is some calcito present in the matrix. (See Fig. 2, Plate 

III.) (Slides402,403.)

C. Vitreous graywacltes.

61. South side of Rove Lake, Minnesota (KB. £, Sec. 28, T. 65, E. 1 E. 

Minnesota). .

A fine-grained, dark-gray, much indurated rock, with conchoidal fracture. This 

rock differs from No. 60 in its larger content of feldspathic and chloritic material. It 

may be taken as the 'type of the rock which forms the larger part of the Animikie 

series. The quartz is the principal mineral and occurs in three phases: (1) in simple 

fragmental grains, always showing some secondary enlargements; (2) in complex 

fragments, which are also occasionally enlarged; (3) as an interstitial material in 

minute interlocking areas. The feldspar fragments include orthoclase and plagioclase, 

and are very plentiful, often closely interlocking with the enlarged quartzes. Sornekaolinic material in the matrix probably represents decomposed feldspars. Some 

chlorite is also present in the matrix. The rock is fully as "crystalline" as anything 

in the original Huronian, to the graywacke-slates of which it is closely comparable, 

especially to the more quartzitic phases of those rocks. It is still closer to some of the 

quartzitic phases of the slate series of the Saint Louis River (e.g., No. 43) and of the 

great series of folded schists of the Knife and Kingfisher Lake region on the national 

boundary. (Slides 1346,1347.)

(220)
inviKG AND VAN HisB.] ENLAKGEMENTS IN ANIMIKIE EOCKS. 37

G3. East end of Mountain Lake (S.W. i, S.W. £, Sec. 13, T. 65, E. 2 E., 

Minnesota.)

A lighter-colored rock than No. 62, but otherwise identical with it. (Slide 1350.)

64. Partridge Falls, Pigeon Eiver, Minnesota.

A feklspathic quartzite or vitreous graywacke, very close to No. 62, differing only 

in having less interstitial material, and, consequently, more thorough interlocking of 

the enlarged quartz areas with each other, and with the feldspar particles. (Slides 

1181, 1328.)

65. South side of Clear Water Lake (near center of Sec. 27, T. 65, E. 1 

E., Minnesota.)

Differs from No. 62 only in being finer grained, being otherwise identical with it, 

macroscopically and microscopically. (Slide 1178.) ' .

66. East side of Thunder Bay, Canada.

A dark-gray rock, near to No. 62, except that it is finer grained and is more argillaceous. The thiu section shows a larger quantity of kaolinic interstitial material than 

Ko. 62, and a larger proportion of chlorite. The usual enlargements of the quartz 

fragments are found. (Slide 432.)

D. Argillaceous graywacke.

67. Grand Portage Falls, Pigeon Eiver, Minnesota.

A fine-grained, light-greenish-gray, argillaceous, not greatly indurated rock. The 

thin section is near to that of No. 62, but shows a very much larger amount of a clayey 

matrix, and less of a siliceous cement. The quartz fragments are often enlarged. 

(Slide 1355.)

IN THE FOLDED SCHIST OP THE NATIONAL BOUNDARY LINE, NORTH OF LAKE SUPERIOR.

68. Kingfisher Lake (S.W. J, S.E. £, Sec. 23, T. 65, E. 6 W., Minnesota.

A dark-gray, fine-grained, vitreous graywacke or quartzite, somewhat coarser 

grained than No. 62 of this series, but otherwise closely like i=t. This resemblance 

holds also in the thin section, except that this rock is, perhaps, somewhat more feldspathic. The quartz fragments are often enlarged. (Slide 1147.)

69. Kingfisher Lake (N.W. £,K E. £, Sec. 26, T. 65, E. 6 W., Minnesota.

A dark-gray, fine-grained rock, resembling the last described, but somewhat 

coarser-grained. Close also to much of the graywacke of the slate-conglomerate of 

Lake Huron. In the thin section, quartz and feldspar fragments, the former often 

enlarged, and the latter including both orthoclase and plagioclaso, are embedded in 

fine matrix composed partly of quartz, but also in part of amorphous silica and kaolin, 

with also numerous particles of oxide of iron. Chlorite is abundant as an alterationproduct of the feldspars. (Slide 1144.)

70. Knife Lake (8. W. J, S. E. J, Sec. 17, T. 65, E. 6 W., Minnesota).

A fine-grained, dark-gray cherty quartzite or quartz-schist. Thefragments of quartz 

are ofteued enlarged. Orthoclase and plagioclase compose about one-half of the rock, 

the remainder being made up of an excessively fine, siliceous matrix material, which, 

in a large measure, has no effect on the polarized light.

It is of considerable interest as bearing upon the question of the structural relation

(221)
38 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

of the rocks of the great slate series, from which these specimens come, to the Auiinikie series south of them, that there should he such a close lithological resemblance 

between the rocks of the two series.25 (Slide 1151.)

KEWEENAWAN SANDSTONES.

71 Eagle Harbor, Keweenaw Point, Michigan.

A red sandstone from the uppermost part of the "great conglomerate." This rock, 

which is made up of the detritus of different acid porphyries, is described in detail in the 

second part of this bulletin, since the induration has been mainly due to the secondary 

enlargement of feldspar fragments. The few grains of quartz contained are observed 

at times to have received secondary enlargements. (Slides 596,1474.)

72. Near Copper Falls Mine, Keweenaw Point, Michigan.

A red sandstone from a layer interstratified with amygdaloids and traps, much resembling No. 71, except that the principal indurating material is calcite. The occasional quartz grains show very distinct enlargements.26 (Slide 526.)

73. North side Portage Lake (Nonesuch Belt 27), Keweenaw Point, Michigan.

A fine-grained, dark-colored, strongly-indurated sandstone, composed in large part 

of the detritus of the acid porphyries and basic rocks of the Keweenaw series, but 

containing also a large proportion of quartz fragments, most of which show distinct 

secondary enlargements. 28 (Slide 614.)

74. Foot-wall of the Nonesuch Mine, Porcupine Mountains, Michigan.

A light-reddish brown, streaked, fine-grained sandstone, composed about two-thirds 

of fragments of basic and acid eruptives, the remainder being quartz fragments, 

many of which are quite angular, and seemed to have broken from the crystals of 

a quartz-porphyry. In many cases these fragments have received secondary enlargements.» (Slide 617.)

75. Little Iron Eiver, (N. W. J, N. W. |, Sec. 12, T. 50, E. 43 W., 

Michigan).

A fine-grained, dark-gray,.much indurated sandstone orgraywacke, the silver-bearing rock of Iron River. The predominant quartz occurs in the two forms of interlocking areas of some size, each with a plainly fragrnental nucleus, and of an independently deposited interstitial material. The quartz fragments are at times finely 

complex. The remainder of the rock is made up of quartz-porphyry detritus, with 

some infiltrated calcite. (Slide 620.)

76. Little Iron Eiver, (S. W. £, Sec. 13, T. 51, E. 42 W., Michigan).

A rock close to the last described and coming from the same " silver belt," differing 

chiefly in having more infiltrated calcite in the matrix. The induration is, however, 

largely due to infiltrated quartz, which occurs both as enlargements to the quartz 

fragments and independently oriented.

The rocks from the same belt on Big Iron River, on the lake shore near Lone Rock,

25 Monographs of the U. S. Geological Survey, Vol. V. pp. 399,417. 

20 For description and figure of this rock, see monograph on Copper-Bearing rocks 

of Lake Superior, p. 129, and Plate XVI, Fig. 3. 

« Op. dt., pp. 193, 220-224.

28 For further description of this rock, ^see Loc. cit., p. 131. 

89 Op. cit., p. 131.

(222)
IRVIKG AND VAN HISS.] ENLARGEMENTS IN CAMBRIAN ROCKS. 39

and in the vicinity of Presqu7 Isle River, except that the "basic detritus and infiltrated 

calcite become more ahundant, present the same appearance. (Slide 655.)

77. Presqu' Isle Elver, (NB. J, sec. 5, T. 49,' E.. 45 W., Michigan). 

Upper sandstones of the Keweenaw series.

A dark-red, fine-grained sandstone, closely similar to the last two described. The 

quartz fragments are both simple and complex, the first often widely enlarged. 

(Slide 355.)

78. Silver Islet Landing, north shore of Lake Superior, Canada.

A fine-grained, cream-colored, indurated sandstone. Angular, often interlocking 

quartz areas, each with a fragmental nucleus plainly outlined, make up most of the 

rock. Independently deposited quartz and some dolomite occur interstitially.30 

(Slides 471, 472.)

79. East side of Black Bay, Lake Superior, Canada.

A fine-grained, red-and-white-streaked, quite indurated sandstone. Subangular 

fragments of quartz, often showing quite wide and distinct enlargements, along with 

feldspar fragments, are buried in a matrix of finer fragmental quartz, which, in the 

 red bands, is mingled with red oxide of iron and, in the white ones, with dolomite. 

(Slide 477.)

80. Burnt Island, Nipigon Bay, Lake Superior.

A fine-grained, brick-red, very much indurated sandstone, almost a quartzite. The 

predominating quartz is in interlocking areas each with a distinctly oiitlined fragmental nucleus the enlargements having at times been very wide and also in the 

shape of an independently deposited finely divided material. The feldspar fragments are plenty, and the rock is stained with oxide of iron. (Slide 491.)

CAMBRIAN ROCKS. 

IN THE GRAND CANON GROUP OF THE COLORADO RIYER.

81. The Grand Canon of the Colorado, near the mouth of the Little 

Colorado Eiver, Arizona.

The specimens from this locality, kindly furnished us by Mr. Walcott, of the U. 

S. Geological Survey, range from a moderately indurated sandstone to nearly wholly 

vitreous quartzite. They are nearly white in color, and consist almost wholly of 

quartz with a minute quantity of iron oxide. The outlines of the original fragments 

are everywhere distinct, but always lie some distance within the individual areas, 

which interlock more or less thoroughly. (Slides 1363-1366 inclusive.)

IN THE POTSDAM SANDSTONE OP THE MISSISSIPPI VALLEY.

82. Immediately above unconformable contact with Huronian iron ores, 

Cyclops and Norway mines, Menominee iron region, Michigan.

A very much indurated, buff to brown sandstone at times almost a vitreous 

quartzite. The thin section is composed, almost entirely, of interlocking grains of 

quartz, each w ith its distinctly outlined fragmental core. There is a little independently deposited interstitial quartz, and a little fragmental feldspar. The rock is in 

no respect different from much that is to be seen among the quartzites of the Huronian. (Slides 959, 960.)

30 For description of this rock see Op. tit., p. 133. 

(223)
40 SECONDARY ENLARGEMENTS OP MINERAL FRAGMENTS. [BULL. 8.

>-

83. Lower Narrows of Baraboo Eiver, from near contact with Archaean 

quartzite.

A much indurated, fine-grained sandstone carrying quartzite pebbles. The quartz 

fragments, originally but little rounded, are all strongly enlarged, so that there is a 

considerable degree of interlocking. There is .also present some fine independently 

deposited interstitial quartz. The section does not differ materially from those of 

many Archaean quartzites. (Slide 742.)

84. Eoche Ecrit. Adams County, Wisconsin.

A dark-purplish, in places very much indurated sandstone. The grains are all enlarged, and occasionally have crystal faces developed. (Slide 749.)

85. Packwaukee, Marquette County, Wisconsin.

A pale, buff-colored, much indurated sandstone, showing only very rare crystalline 

facets. In the thin section the grains are seen to have been enlarged slightly, so as 

to fit closely without any dovetailing. Occasionally the enlargements have had an 

opportunity to develop crystal faces. (Slides 731,732.)

86. Black Eiver Falls, Jackson County, Wisconsin.

A white, rather coarse-grained rock, not so much indurated as the last-described, 

aud showing more crystal facets, although not very plentifully. The thin section is 

much like that of the rock last described, except that the enlargements are proportionally broader and have more often developed crystal faces. (Slides 733, 734.)

87. New Lisbon, Wisconsin.

A fine-grained, pink-and-white-mottled sandstone, from which the light is reflected 

in numerous sparkling points. The induration, while distinct, is only slight, small 

fragments crumbling readily in the fingers. The crumbled sand mounted in balsam 

shows every grain enlarged, the lines of junction between the old and new quartz being always strongly marked. The enlargements have in all cases developed crystalline faces, which are, however, only perfect and uninterrupted upon the smallest of 

the grains. In most cases they are more or less indented b,y the enlargements of contiguous grains. This rock may be taken as a type of the crystal-faceted sandstones. 

(Slides 710 to 716 inclusive.) (See Figs. 4,5,6, Plate II.)

88. Middleton, Dane County, Wisconsin. 

A fine-grained, loose, white sandstone, showing the grains sparkling from crystal 

facets. The balsam mounting of the sand crumbled from the rock shows the grains 

with the usual cores and crystal outlines. (Slides 1469, 1470.)

IN THE EASTERN SANDSTONE OP LAKE SUPERIOR.

89. West Branch of the Ontonagon Eiver (Sec. 13, T. 46, E. 41 W., 

Michigan).

A reddish, coarse-grained, indurated sandstone. The quartz fragments which make, 

up the rock have all been enlarged, sometimes very much so, so as to interlock. 

There is also some independently oriented fine interstitial quartz. Some much reddened, feldspathic detritus is included. (Slides 95, 96, 97.)

90. Quarry on Torch Lake Eailroad, Keweenaw Point, Michigan.

A white to pinkish, feebly indurated quartzose sandstone. Some of the less indurated portions show numbers of faceted grains. The slide here described is from 

one of these less indurated portions. It is seen to bo made up almost entirely of much 

rolled quartz fragments, which have in nearly every instance been enlarged, the enlargements only occasionally showing crystalline outlines. These crystal outlines

(224)
IHVING AND VAN HIBE.] ENLARGEMENTS IN SILURIAN ROCKS. 41

s . 

are, however, more frequently to he seen in the balsam mounting of crumbled sand. 

They are not nearly so numerous, however, as in some of the rocks previously described, the grains having interfered too much to form crystal outlines. The outlines 

of the original grains are usually very strongly marked by brownish iron oxide. 

There are occasional rounded fragments of feldspar present, and in each thin section 

may be seen a few particles worn from some of the fine-grained Keweenawan ernptives. (See Figs. 7,8,9, Plate II.) (Slides 513,514,1471,1472,1473.)

See with regard to this rock also Copper-Bearing rocks of Lake Superior, pp. 356- 

358. See also for an earlier description M. E. Wadsworth in Bull. Mus. Comp. Zool., 

Vol. VII, No. 1, p. 117. Wadsworth found the crystal-outlined grains abundantly in 

his sections, although we failed to do so in ours until recently. He regarded these 

crystal grains as being the usual dihexahedral crystals of quartz-porphyries, on which 

view the crystals antedate the formation of the sandstone instead of being subsequent to it. More recently (Science, Vol. II, No. 23, p. 52, July 13,1883) he has reasserted this view. Bat a careful re-examination of this rock, as also of others from 

other places within the area of the Lake Superior sandstone, lias served to convince 

us that in all of these cases, as in all sandstones yet examined by us, provided with 

such faceted grains, they owe their crystal faces to secondary enlargements of rolled 

fragments. Ifc is of course possible and even probable that these quartz fragments 

were once, some of them, the quartzes of quartz porphyries, but if so they have rarely, 

if ever, retained their crystal faces, as it is, indeed, hardly conceivable that they 

should do.

91. Quarries at Marquette, Mich.

A reddish, fine-grained sandstone, showing numerous minute glistening flakes of 

mica. Quartz fragments make up rather more than half of the rock, many of the 

grains being finely complex. The simple quartz grains are mostly very angular; 

many of them show very distinct enlargements. Tho»remainder of the rock is composed chiefly of fragments of feldspar, including othoclase and plagioclase, with 

chlorite, brown iron oxide, and muscovite flakes, the chlorite having resulted from 

the alteration of the feldspars. The plagioclase includes quite a number of large-sized 

pieces of niicrocline.

92. Near Eockland. South of the Trap Eange (S. E. £, Sec. 7, T. 50, E. 

39 W., Michigan).

A fine-grained, feebly indurated, pinkish, quartzose sandstone, sparkling from presence of crystal facets, each quartz fragment being enlarged, the enlargements being 

often provided with crystalline outlines. (Slides 1475,1476.)

IN THE WESTERN SANDSTONE OP LAKE SUPERIOR.

93. Basswood Island, Ashland County, Wisconsin.

A fine-grained, feebly indurated, white sandstone, containing besides the quartz 

many feldspar fragments. The quartzes are often enlarged, the enlargements being 

in many cases supplied with crystal facets. (Slide 53, Wis. sur. series.)

SILURIAN BOCKS. 

IN THE SAINT PETER'S SANDSTONE OP WISCONSIN.

94. Near Lancaster, Grant County, Wisconsin.

This rock is represented in our list only by slides kindly furnished by the Rev. A. A. 

Young, of New Lisbon, Wis. They are dry mountings of the sand crumbled by hand 

from the rock. The grains are furnished with crystal facets from secondary deposition.^ (Slides 707 to 711.) . '.

31 Amer. Jour Sci., July, 1883. 

(225)
42 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BOIL a.

95. Arlington Prairie, Columbia County, Wisconsin.

The Arlington Prairie is part of a large elevated area underlain by the Lower 

Magnesian Limestone, but dotting it here and there are small outliers of the Saint 

Peter's sandstone. A group of these outliers occurs in the southwestern part of the 

town of Arlington. 32 Most of the rock of these outliers is quite loose, and of the ordinary character of the Saint Peter's sandstone. Along its weathered surface, however, 

and along the sides of joint cracks, it is very much indurated, becoming even a completely vitreous quartzite for the distance of one-fourth or one-half an inch inwards 

from the surface. Sections of this completely vitrified portion show the quartz fragments with enlargements that everywhere fit closely together or interlock, but sections taken from an inch or two below this crust show the enlargements frequently 

furnished with crystal facets, the enlargements having interfered with one another 

sufficiently to give a slight induration. Fig. 1, Plate III, shows the appearance of a 

thin section of this less indurated portion as seen in the ordinary light. 33 (Slide 724).

96. Gibraltar Bluff, Columbia County, Wisconsin.

A very much indurated, fine-grained rock, in which a fine arenaceous texture is 

visible only upon the closest inspection. The rock is one which, if found among the 

crystalline schists, would undoubtedly be classed as a true quartzite, and the appearance of the thin section would entirely bear out this classification. It is made up 

only of interlocking grains of quartz of two very different sizes, the larger ones predominating. The large ones of these areas, and many of the smaller ones, show each 

a more or less plainly outlined fragmental nucleus. The areas interlock, often very 

intricately, and in every possible sense the rock is fully as "metamorphic" as any 

quartzite yet studied from the Archaean formations, and yet it is a mere local phase 

wholly independent of any igneous or other apparent metamorphosing action, in a 

formation whose ordinary character is that of an incoherent sandstone. In no Archaean quartzite that we have^examined is the interlocking of the quartz areas, and the 

consequent appearance of complete original crystallization, more marked than in this 

sandstone.3* See Fig. 1, PL V. (Slide 727.)

IN THE EUREKA QUARTZITE OF NEVADA.

97. Eureka, Nevada.

This rock and the three following' are the ones in which Hague and Iddings noted 

enlargements of quartz grains as long ago as the summer of 1881. They Will he found 

fully described in Hague's monograph upon the Eureka district. Mr. Hague has been 

kind enough to furnish us specimens and slides for the purpose of comparing them 

with quartzites which we had examined. The specimen of Eureka quartzite furnished 

by Mr. Hague would be classed by us as a semi-vitreous quartzite. The enlargements 

of the quartz fragments of which the rock is composed has produced close fitting but 

never any considerable interlocking. But still the rock is fully as much altered as any 

of the true Huronian quartzites.

DEVONIAN.

98. Sandstone from the White Pine shale, Eureka, Nevada.

A fine-grained, strongly indurated sandstone, composed of fragments of quartz and 

of chalcedonic or amorphous silica. The quartz fragments are often enlarged and 

are sometimes furnished with crystal faces. (Slide 1436.)

^Geol. of Wis., vol. II, p. 583.

33 For figures drawn from the vitrified crust of this rock see Amer. Jour. Sci., June, 

1883, p. 407.

34 Amer. Jour. Sci., June, 1883, p. 408.

(226)
IEVKO AND VAN KIBE.] ENLARGEMENTS IN CARBONIFEROUS ROCKS. 43

CARBONIFEROUS.

99. Eureka, Nevada, Diamond Peak quartzite.

A fine-grained, greenish-drab, feldspathic quartzite. In the thin section feldspar, 

often much altered, is seen to.compose a large proportion of the rock. The minute 

grains of quartz show relatively wide enlargements. (Slide 1368.)

TRIASSIC.

100. Henry Mountains, Utah.

A light-gray to pinkish, fine-grained, feebly indurated sandstone from near contact 

with one of the laccolites. Small rounded grains of quartz compose the larger part 

of the rock. These have often been enlarged, and the enlargements fit somewhat 

closely. There- are some grains of feldspar and, interstitial ly, calcite, fine quartz, 

clayey material, and iron oxide. (Slide 1367.)

CRETACEOUS.

101. Courtlandt, Nicollet County, Minnesota.

A light-gray, compact, calcareous sandstone, consisting of quartz fragments embedded in a matrix of crystalline calcite. The quartz fragments, only rarely in contact with each other, have quite often been enlarged. (Slide 1384.)

(227)
II.

ENLARGEMENTS OF FELDSPAR'FRAGMENTS IN CERTAIN

KEWEENAWAN SANDSTONES.

BY C. B. VAN HISE.

For some time past I have been on the outlook for evidence of the 

secondary enlargement of feldspar fragments. In the slate conglomerates of the north shore of Lake Huron (as mentioned in Part I of 

this bulletin) I have found what may be enlarged feldspar grains, but 

the evidence is not sufficiently satisfactory that any of the material is 

of secondary origin, the lines of separation between the supposed new 

material and the nuclei being illy marked. However, I have found what 

seem to be additions to grains of that mineral in certain of the Keweenawau feldspathic sandstones. The specimens in which the supposed 

enlargements were first found are taken from those portions of the sandstones almost in contact with overlying basic eruptives. This position 

is evidently a favorable one for the development of such enlargements, 

the heated alkaline waters which would naturally descend supplying 

appropriate conditions. Then, too, quartz enlargements, when most 

easily found, are shown by lines of ferrite about the nuclei, and are ordinarily best seen in the less indurated quartzites. The Keweenawan 

sandstones are highly ferruginous, and are of an open texture; hence, 

if in them the feldspar fragments have taken new growths, the conditions for their detection are favorable.

The feldspathic sandstone immediately underlying the diabase of 

Eagle Harbor, Michigan, is of a uniform medium grain, a magnifying 

glass showing but little quartz. The feldspar grains are stained red 

with iron oxide. Hydrochloric acid gives with the powder a slight effervescence. In the thin section the sandstone is seen to be composed 

largely of grains of different feldspars, next to which in abundance are 

rounded complex fragments derived from a granitic porphyry,1 consisting of feldspars penetrated by a saturating quartz. Then follow in 

order of abundance complex fragments of some altered basic rocks. 

Finally, a few grains of quartz and a little secondary calcite are noted.

The feldspars are frequently somewhat kaolinized, but most of the 

grains are fresh enough to give quite uniform colors in polarized light, 

and, in the cases of the plagioclases, well denned twinning bands. The 

grains are all rounded, their boundaries being broad lines of ferrite. 

However, some subsequent mineral has used these grains as nuclei

° ' Third Annual Keport U. S. Geol. Survey, p. 114. 

44 (228)
IBVING AND VAN HISE.] ENLARGENENTS OF FELDSPAR FRAGMENTS. 45

about which to deposit, and now each individual appears in the polarized light to extend beyond its original limits. The newly formed borders as compared to the interiors are different, in that they show no 

decomposition and are freer from iron stains. When the borders from 

different feldspathic grains have extended so far as to come in contact, 

as they usually have done, they form sharply serrate, nicely fitting 

junctions, roughly comparable to the suture of a skull (Fig. 1).

Fig. 1. Portion of section of E agio Harbor sandstone enlarged 50 diameters. AAA, feldspar fragments, bounded by oxide of iron borders, aaa, outside of which, are enlargements, EBB, of the grains 

polarizing in each case with the nucleal fragment as'indicated by the shading. C is a quartz fragment, D unfilled spaces, and E supposed secondary feldspars polarizing independently of the original 

fragments.

This newly added material appears to be feldspar, which has co-ordinated crystallographically with the grains about which it has deposited. 

It possesses no optical properties which would exclude that mineral, 

but cleavage and decomposition being absent, no comparison with feldspars can be made as to those characteristic features. The belief that 

the new material is feldspar is, however, based upon the folio wing facts :

When the enlarged feldspar is orthoclase, the deposited substance 

polarizes uniformly with the nucleus about which it is seen (Fig. t) exFig. 2. Enlarged fragment of. triclinic feldspar in the Eagle Harbor sandstone, shaded so as to 

show how the fragment and enlargement [polarize together. The black line is the heavy oxide of iron 

border of the original fragment.

(229)
46 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

actly as quartz enlargements polarize with the grains on which they 

have grown. Further, when plagioclase fragments present the enlargements, as they frequently do, the new material is twinned uniformly 

with the old, the twinning bands in polarized light running directly 

across cores and borders (Fig. 2). This phenomenon was observed in 

many different grains and in different sections.

Again, the complex fragments above mentioned as derived from a 

granitic porphyry, containing quartz and feldspar, often have enlargements, and the added portions resemble and usually polarize with the 

feldspars instead of with the quartz, with which they would naturally 

co-ordinate, if with either, were they composed of silica. Frequently 

the enlargements of this class of grains are apparently all of feldspar, 

even when a half or more of the edges of the original fragments (and 

in some places for considerable spaces continuously) are quartz (Fig. 3).

Fig. 3. Enlarged fragment of feldspar, including some quartz, from the Eagle Harbor sandstone. 

The shading shows the feldspar fragment polarizing with the nucleus, even where not in contact with 

it. The black line is the oxide of iron border of the original fragment.

Finally, the complex basic fragments also have enlargements. These 

basic grains are often very feldspathic, the feldspar individuals being, 

however, small. Here a border, instead of being a unit, as it commonly 

is in the preceding cases, consists of several, or many individuals. The 

feldspars at the edge of the nucleus appear to have controlled the new 

growth, so that the new material polarizes with them in separate parts. 

These parts have, however, often extended upon each side beyond the 

immediately adjacent feldspars of the nucleus, and thus at times overlapped other feldspars whose conditions were less favorable for renewed 

growth, or other minerals, if such chance to b& in contact with the 

division line between the fragment and its border.

The change which has taken place in one grain of orthoclase is of 

some interest. The grain has been broken into two parts, which have 

spread somewhat, and is now cemented with a new material which 

extinguishes with the original fragments, and also with the exterior 

second growth with which it is continuous in one place (Fig. 4.)

In some cases the new material deposited on a grain, instead of continuing as a single individual until it meets a similar growth from an-

(230)
IRVIHG AND VAN HME.1 ENLARGEMENTS OF FELDSPAR FRAGMENTS. 47

other grain, has crystallized independently in small interlocking grains 

(Fig. 1). This independent feldspar (if I am correct in. so considering

Fig. 4. An enlarged fragment of orthoclase from the Eagle Harbor sandstone. This fragment has 

been broken across and cemented by a material that polarizes with the original fragment and the 

enlargement. The black line is the oxide of iron border of the original fragment.

it) is more plentiful about the basic fragments than about the feldspar 

grains or those of the granitic porphyry. , Uncovered thin sections were examined with acid, and the supposed 

feldspar enlargements found not to be affected. An attempt to test 

for hardness was not very successful. Micro-chemical tests from the 

nature of the case could hardly be applied.

This same secondary material has been found in other localities in 

the Keweenaw series, and in two cases the sandstone directly underlies 

eruptive greenstone.

(231)
III.

SUMMARY OF GENERAL CONCLUSIONS.

By E. D. IRVING.

Genesis of 'Huronian quartzites. All the true quartzites of the Huronian 

are merely sandstones which have received various degrees of.induration 

by the interstitial deposition of a siliceous cement, which has generally 

taken the form of enlargements of the original quartz particles, less 

commonly of minute independently oriented areas, and still less commonly of chalcedouic or amorphous silica; two, or even all, of the three 

forms occurring at times in the same rock. There may have been in 

some cases some solution and redeposition of the original quartz material, but in the main these rocks are still made up of the fragmental constituents that composed them before induration, the fragments retaining 

for the most part their original contours. That these quartzites are but 

altered sandstones is, of course, a truth which has long been generally 

recognized; it is the nature of the alteration that has not been understood.

It should be said that the term " Huronian " is here used, provisionally 

at least, to cover (1) the original Huronian on the north shore of Lake 

Huron, east'of Sault Sainte Marie; (2) the iron-bearing formation of the 

Marquette and Menominee regions of Michigan and Wisconsin; (3) the 

slaty rocks of the Wisconsin Valley in the vicinity of Wausati; (4) the 

iron-bearing rocks of the Penokee-Agogebic range of Northern Wisconsin and Northwestern Michigan; (5) the cleaved slates of the Saint 

Louis and Mississippi Eivers in Minnesota; (6) the quartzites of the 

Chippewa Eiver region of Western Wisconsin; (7) the iron-bearing 

schists of Black Eiver, Wisconsin; (8) the quartzites of the Baraboo 

region, Southern Wisconsin; (9) the red quartzites and sandstones of 

Southwestern Minnesota and Southeastern Dakota; (10) the Animikie 

series of the Thunder Bay region, on the north shore of Lake Superior, 

and thence southwestward to Pokegaina Falls, on the Mississippi Eiver; 

and (11) some, at least, of the folded schists of the national boundary 

line.

Huronian quartzites no more " metamorpliic" than numerous sandstones 

of later formation. Without perhaps being definitely so stated, the generally accepted view with regard to the production of quartzites from

. 48

(232)
IRVING AND VAN KIBE..] GENESIS OF HURONIAN QUARTZITES. 49

sandstones has included the idea of a more or less thorough molecular 

rearrangement and recrystallization of the original fragmental material, 

quartzites having generally been classed as metamorphic or often even as 

crystalline rocks. But, so far as the Archaean quartzites of the Northwest are concerned, it appears that they have undergone no other alteration than that found to affect sandstones in the later and unaltered 

formations in all periods down to the Cretaceous. Irregular areas, and 

at times mere surface films 35 in the otherwise unaltered horizontal 

Potsdam and Saint Peter's sandstone in the Mississippi Valley have been 

changed to vitreous quartzites, indistinguishable microscopically and 

macroscopically from the quartzites of the Archaean, while great beds 

of as completely indurated quartzite as any of the Huronian are met 

with in the unaltered Paleozoic formations of the West. These later 

quartzites are plainly due to the interstitial percolation of silica-bearing 

waters, and to the same cause must be attributed the induration of the 

Huronian quartzites. In the case of the quartzites of the indurated portions of the Potsdam and Saint Peter's sandstones, no possible connection 

with any igneous action can be conceived, the surface crusts being due 

to a mere weathering, the interstitial silica-bearing waters having been 

drawn to the surface by evaporation and capillary action. These crusts 

are particularly interesting, because they are evidently in process of 

formation at the present time, occurring wherever the accidents of denudation have produced exposed surfaces of the rock, and one cannot conceive that either heat or pressure is concerned in their production, and 

yet they are as completely vitreous and crystalline as any of the true 

quartzites of the Huronian.

In the case of the quartzites of the Huronian and other formations 

where there is much interstratified eruptive material, the latter may 

have been the source of heated silica-bearing solutions, but I can see 

no reason to believe that there has been any other causal relation between igneous action and the induration of the sandstones than this.

It is of interest to note in this connection that since the quartzites of 

the various Huronian areas, and indeed the larger part of the other 

non-eruptive Huronian rocks, are in no sense more altered than any fossil-bearing quartzites, etc., of later formations, it maybe taken as quite 

certain that the failure thus far to find fossils in the Huronian is not to 

be attributed to their destruction by metamorphic action, but rather to 

an actual, original barrenness of the series.

Other rocks in the Huronian than true quartzites have been affected by a 

siliceous induration. It also appears that, besides the true quartzites, 

other rocks of the Huronian for instance the graywackes in which 

quartz is merely a subordinate, or at least not the principal, ingredient

35 See Hawes's Lithology of New Hampshire, p. 239; Dana's Geology, p. 70; Geikie's 

Geology, p. 117,127 ; Hawes noticed the complex character of some of the quartz fragments of certain New Hampshire quartzites, and took it to mean that these grains had 

heen recrystallized rather than that they were originally complex.

(233) 

Bull 8 4
50 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BOLL. 8.

have been affected by the same sort of siliceous induration, the indurating silica occurring both as enlargements of the quartz fragments and 

independently of them. Accompanying this induration there has been 

at times a replacement of feldspathic material by quartz, and the alteration of feldspar to chlorite, the chlorite occurring both as a pseudomorphic substitute for the feldspars, and independently crystallized in 

the interstices. Probably, also, the feldspar fragments have received 

secondary enlargements analogous to those described by Mr. Van Hise 

in Part II of this paper. By one or more of these processes rocks have 

been changed so as to present macroscopically and microscopically the 

appearance of more or less complete original crystallization, and yet 

they are made up almost entirely of the original fragmental material, the 

alteration which they have undergone having been merely metasomatic, 

and not " metamorphic " as the term is generally understood.

Besides the graywackes some at least of the mica-schists of the Huroniau are mainly made up of the original fragmental material, unaltered, in some cases mingled with mica that appears to have developed 

in situ, the quartz grains often showing enlargements.

" Metamorphism " in the Huronian generally. In the various Huronian areas above enumerated, one or more of quartzites, graywackes, 

and clay slates, with intermediate phases, make up most of the series, 

from which it follows that the bulk of the Huronian is made up of rocks 

not properly falling under the term metamorphic.36 I may say, indeed,

36 1 am aware that the Huronian has often been spoken of as characterized mainly by 

other rocks than quartzites. In "Azoic Rocks" (Sec. Geol. Sur. Penn., p. 70.), Hunt 

speaks of Murray's first exploration of the north shore of Lake Huron as showing the 

existence there of " a.great series of chloritic slatesand conglomerates with interstratified greenstones, quartzites, and limestones." Murray's own words (Report Geol. 

Sur. Canada, 1847-1848, p. 109) are, "A set of regularly stratified masses, consisting 

of quartz rocks, or altered sandstones, conglomerates, slates, 'and limestones, interstratified with beds of greenstone." " Under the denomination of slates are included 

various thinly laminated dark green, blackish, and reddish rocks, some of which are 

very chloritic and some contain epidote." In Logan's description of the series (Geol. 

of Canada 1863, p. 55, and atlas to the same, Plate III) the Huronian section between 

the Mississaugi and Saint Mary's Rivers is made to include 10,820 feet of quartzites, 

4,280 feet of slate conglomerates, 2,000 feet of '' chloritic and epidotic slates and traplike beds," and 900 feet of limestone and chert. Of the " slate-conglomerates " a large 

proportion is qnartzite, the balance being the gray wacke, gray wacke-slates, and graywacke-conglomerates of the first part of this paper. It should be said that the various intercalated greenstone layers of the series are included by Logan in these measurements. Having carefully examined the ground myself, I am convinced of the 

general correctness of Logan's section. At least two-thirds of the series is made up 

of quartzite. Of the balance the graywackes of the slate-conglomerate make up at 

least one-half. Of the remaining sixth, one-third is limestone and chert and the balance "chloritic and epidotic slates, and trap." But these chloritic and epidotic slates, 

which, although so insignificant a portion of the series, have been made to serve as 

its most prominent characteristic, are, as I have convinced myself by examining them 

/ in their typical development east of Thessalon Point and in the thin sections, merely 

' eruptive, diabasic greenstones in various degrees of alteration. It is possible (hat 

the occurrence of the greenish .chloritic graywackes in the slate-conglomerates has

(234)
IRVING AND VAN RISE.] MINERAL ENLARGEMNETS IN ROCK ALTERATION. 51

although the matter cannot be discussed in this place, that as my 

studies progress, rocks in the Huronian, to which the term " metamorphic" meaning that they are altered from fragmental sediments, but 

now consist chiefly or wholly of material crystallized in situ would 

properly apply, grow fewer and fewer, those that remain being restricted almost entirely to regions where the series is highly folded.

Mineral enlargements in rock alteration generally. The wide-spread 

importance of the enlargement of quartz fragments in the production 

of quartzites and other quartz-bearing indurated rocks being proved, 

naturally the lithologist is led to query as to whether fragments of 

other minerals, each after its kind, may not have received secondary 

enlargements, and, if so, how far such enlargements may have been concerned in the production of" metamorphic rocks." As a partial answer 

to this query we can offer the enlarged feldspar fragments of certain 

Keweenawan sandstones, described in Part II of this bulletin, and the 

apparent enlargements of feldspar fragments in certain of the feldspathic graywackes of Lake Huron. Farther than this we have as 

yet nothing to offer. Certainly the field is one deserving of investigation. We have not studied any gneisses or similar rocks since our 

attention was drawn to this matter. Theoretically, one can easily see 

how such enlargements might be of great importance in the production 

of the crystalline schists, the enlargements being accompanied, perhaps, 

by partial solution of the fragmental material, and by processes of replacement and pseudomorphism, and by some recrystallization, -pressure coming in to produce the foliation. As noted before, Bonney has 

already suggested the importance of this matter of enlargement of 

mineral fragments. His words are worth quoting here in full. Speaking of certain banded crystalline schists of the Lizard district, Cornwall, England, he says:

"It seems, then, possible to me that in these and in some of the curiously-banded rocks in the upper groups, many of the constituents 

may be in part original. I do not mean that any one grain, as it now 

stands, is an original constituent; crystallization in situ, especially in 

the case of hornblende and mica, has taken place to a large extent. In 

the more minutely crystalline schist, the original structure is very prob 

ably wholly obliterated. Still, these large feldspar grains, for instance, 

may have as their nucleus feldspar grains which were original constituents, and may have survived the dissolution of the finer sedimentary 

materials in which they were imbedded. Then, in the process of reconstitution, feldspar (not perhaps always of the same species) may have 

been added to feldspar, quartz to quartz, mica to mica, and hornblende 

to hornblende or altered augite. This traces of the minuter structure of

contributed to the idea that chloritic and epidotic crystalline rocks are its main characteristics. The type Huronian, then, i. e., that of the area between the Mississaugi 

and Saint Mary's Rivers; should be described as a great quartzite series, including subordinate quantities of graywacke, limestone, chert, and eruptive greenstones.

(235)
52 SECONDARY ENLARGEMENTS OF MINERAL FRAGMENTS. [BULL. 8.

the original rock, even in a highly metamorphosed series, may now and 

then remain. In those beds where the chemical composition of the 

constituents facilitated change, or where the materials were finely levigated, the agents of metamorphism reduced the whole to a mere pulp 

(if the expression be permissible) from which the present mineral constituents crystallized, almost as they would do from the magma of an 

igneous rock; but in other cases, only a portion of the material was 

reduced to this condition, and those constituents which remained undigested would form nuclei around which the other minerals would crystallize, and would so continue to bear testimony to the original history 

of the rock itself. Thus the explanation of those granitoid bands, in 

some cases so curiously like granite veins, may be that originally they 

were a rather coarse quartz-feldspar grit. As regards some of the 

hornblende schists, one would suggest the possibility (as I believe has 

been elsewhere done by the late Professor Jukes) of their having been 

basaltic tuft's, with which in chemical composition they would agree 

fairly well.

"I have ventured on this digression because these Cornish rocks have 

presented structures which seem to me worthy of careful consideration 

by all who are studying the phenomena of metamorphism a subject 

which has occupied my attention for some years past. The observations are not entirely novel. Dr. Sorby drew attention to somewhat 

similar structures in his very valuable and suggestive paper on the 

original constitution and subsequent alteration of mica-schist. The 

agglutination of identical mineral matter has been noticed in the case 

of quartz by that author, by Mr. J. A. Phillips, and by myself independently, not tq mention others. In the gneissic series traversed by 

the upper part of the St. (Jothard Pass, and in other districts, I have 

repeatedly noticed similar instances, all tending to show that the minute 

Structures, and in some cases very probably the original constituents 

(at any rate as nuclei), may be preserved in rocks which are metamorphic in the fullest sense of the word.

"I trust some day to treat the subject more fully; -but I take this opportunity of calling attention to it, because I believe that in it we find 

a clue which may ultimately enable us to solve many difficulties in that 

most perplexing inquiry the relation of the metamphoric and of the 

igneous rocks." 37

"(Quarterly Journal Geol. Soc. Lond., xxxix, p. 19.) 

(236)
INDEX.

Ableman's, Wis., Quartz-schist of........

Animikie Quartzite of Pokegama Falls... 

Animikie Series, Cherty rocks of ........

 , Grey wackes of.....................

 , Quartz enlargements in rocks of.. 20,32,

 , Quartzites of.......................16,

Arlington, Wis., Sandstone of............

Bad Kiver, Wis., Greywacke of..........

 , Qaartzite of.....................

Baraboo Region, Wis., Huronian of......

 , Quartzite of.....................

 , Quartz-schist of.................

 , Sandstone of.....................

Basswood Island, Lake Superior, Sandstone of... ............................

Black Bay, Lake Superior, Sandstone of. 

Black River Falls, Wis., Sandstoue of....

 , Wis., Huronian of..................

Bonney on Enlargements of Mineral Fragments ..................................13,

Brace Mine Bay, Lake Huron, Quartzite 

of......................................

Caledonia, Wis., Quartzite of.............

Cambrian Rocks, Enlargements of quartz 

fragments of............................

Campement d'Ours Island, Greywackeof 

vicinity of.....................

 , Quartzite of vicinity of..........

Champion Mine, Mich., Quartzite of......

Cherty Rocks, Enlargements of quartz 

fragments in.....................

 , of Animikie Series .................

 , Origin of ..........................

 of the Huronian ....................

 Marquette region .............

 Penokee region................

 Potsdam Sandstone ...........

 , Relation of, to thejasperyiront)res.. 

Chippewa Valley, Wis., Hurouian of..... 

Clay Slate, Enlargement of quartz fragments in. .........................

 of Knife Falls, Minn................

 Mahtomah, Minn.......'..........

 Saint Louis River, Minn..........

Clearwater Lake, Minn., Grey wacke of... 

Colorado Canon, Sandstones of...........

Complex quartz fragments. Enlargements

of................................^.....

Conclusions, General.....................

Copper Falls, Mich., Sandstone of........

Courtlandt, Minn , Sandstone of..........

Cretaceous rocks, Enlargements of quartz

fragments in ...........................

Crusts, Quartzitic, A. Geikie on...........

 , of Potsdam Sandstone..............

 , of Saint Peter's Sandstone .........

33

48

20

19,36

35,37

35,48

42

20

31

48

0900

33

40

41

39

16,40

48

51-52

23

33

39

27

24

17

20-21

20

21

21

20

20

21

21

48

20; 32 

32 

32 

32 

37 

39

18

48-52 

38 

43

43

13

49

16,49

"Crystallized" Sandstone, Commonness of 14 .

 , Daubre'e on. .... ................... 12

 , Gerhard on. ........................ 12

 , Huronian .......... ..........15, 26, 30,"32, 35

 , Illustrations of, PI. II. ............. 14

 , Naumann on ....................... 12

 of Arlington, Wis. .................. 42

 EastNeebish. .................... ' 15,26

 Lancaster, Wis........ ........... 15,41

 Madison, Wis .................... 15

 Mount Whittlesey, Wis. ......... 32

 New Lisbon, Wis.

 - Oolite...:.......-

(237)

 Penokee Gap, Wis ...............

 Potsdam Sandstone ........ 12, 15, 16,

 Rodstone, Miun ..................

 Southern Wis ....................

 Spurr, Mount, Midi ..............

 Saint Peter's Sandstone ....... 12, 15,

 the Vosges, France. ..............

Dakota, southeastern, Quartzites of ......

Daubr6e on ' ' crystallized ' ' sandstones ....

 of the Vosges ..................

Del ton, Miun., Quartzite of. ..............

Devil's Lake, Wis., Sandstone of ........

 quai tzite of ......................

Devonian Rocks, Enlargement of Quartz 

fragments in ..............................

Dikes in quartzite of Lake Huron ........

Eagle Harbor, Mich., Sandstone of. ......38,

East Neebish Island, Crystallized sandstone of ........................

 , Quartzite of ....................;

Echo Kiver, Canada, Quartzites of .......

Enlargementsof complex quartz fragments

 feldspar fragments ..................

 in Keweenawan Sandstones . . .

 in Huronian Grey wackes. . ....

 mineral fragments, Bonney on ..... 13,

 in metamorphism ..............

 orthoclase fragments ................

 plagioclase fragments ...............

 quartz fragments, Fading of, into 

matrix ......................

 , Hague and Iddings on ........

 , Historical account of ......... 

 in Animikie rocks. ............

 Cambrian rocks. ............

 Carboniferous rocks ........

 Cherty rocks................

 Clay slates...... ............

 Cretaceous rocks...... ......

 "Crystallized" sandstones.. 13,

32, 35, 38,

 Devonian rocks ...............

53

15

- 11 

11

15,32 

18, 40 

15,35 

15 

30

41, 42 

12 

34 

12 

12 . 

35

15, 34 

34

24 

44-47

15, 26

25 

25, 26

18

44-47 

44-47 

19, 27 

51, 52

50

45

46

17, 20 

13

11-13

35-38

39

43

20,21

20,32

43

16, 26

40, 41

42
54 INDEX.

Enlargement of quartz fragments in Diamond Peak qnartzite of 

Nevada .................. 43

 Eureka quartzite of Nevada. 42

 feebly indurated sandstones. 16,26,32, 

34, 35, 38,40,41, 43

 "Gannister" of Yorkshire.. 11

 Greywackes .18,19,26,27,32,36,37,38

 Hurouian rocks ............. 23

 Keweenawan sandstones.... 38

 loose sandstones ......M, 13-16, 23,35

 mica-schists ................ 21, 30, 31

 Potsdam sandstones......... 39,40

 quartz-schists ........25,26,29,31,33

 sandstone of Henry Mountains....................... 43

 Silurian rocks :............. 41

 strongly indurated sandstones ...........16,36,38,39,40,42

 Triassic rocks .............. 43

 Trinidad sandstone......... 11

 Vitreous quartzites .... .16-18,23-26, 

27-29, 30, 31, 33, 34, 35, 36

 ^ White Pine shale ........... 42

 List of rocks showing....... 23-43

Feldspar fragments, Enlargements of.... 44-47

Fossils, Absence of, from Huronian ...... 49

Freedom, "Wis., Quartzite of.............. 33

Gannister of Marquette, Mich............ 17,28

 Yorkshire, Eng..................... 11,14

Geikie on greywackes.................... 19,20

 induration of sandstone by weathering................................ 13

Gerhard on crystallized sandstones....... 12

Gibraltar Bluff, Wis., Sandstone of ...... 16,42

Grand Portage Falls, Minn., Greywacke of 37 

Grand Rapids, Wis., Sandstone of........ 16

Grey wacke of Bad River, Wis ........... 20

 Campement d'Ours, Lake Huron. ... 27

 ClearwaterLake, Minn............. 37

 Grand Portage Falls, Minn ......... 32

 Keweenaw Point, Mich ............. 20

 Kingfisher Lake, Minn ............. 37

 Xnife Lake, Minn................... 20, 37

 Mountain Lake, Minn .............. 37

 Nonesuch Belt...................... 20

 Palladrean Islands, Lake Huron .... 26

 Partridge Falls, Minn .............. 37

 Rove Lake, Wis .................... 36

 Saint Lonis River, Minn ............ 32

Greywackes, Enlargements of quartz fragments in.............. 18, 19, 26, 27, 32, 36, 37, 38

 , Geikie on ............................. 19,20

 , Induration of Huronian .............. 49-50

 of Animikie Series..................... 19,32,36

 Keweenaw Series................... 38

Hague and Iddings on enlargement of feldspar fragments......................... 13

Henry Mountains, Utah, Sandstone of... 43 

Historical account of enlargement of 

quartz fragments....................... 11

. Huron Lake, Bruce Mine Bay, Quartzites

of...:...,............................... 23

 , Dikes in quartzites of.............. 24

1 Page. 

Huron Lake, Quartzites at McLennan's

Landing....................... 17,24

 , near Thessalon Point............ 23

 , of North Shore.................. 24

 , Saint Joseph's Island......... 26

Hnronian, Absence of fossils from...... ^. 49

 , Chertzrocks of the................... 21

 , Crystallized sandstone.......... 15,26,30,32,35

 , Greywackes, Enlargment of feldspar

fragmentsin .1...................... 19,27

 , Metamorphism in the.................19,49,50

 of Baraboo region, Wis ................ 48

 Black River, Wis ................... 48

 Chippewa Valley, Wis.............. 48

 Marquette region................... 48

 Menominee region .................. 48

 Penokee region ..................... 48

 -^ Southern Minnesota ................ 48

 Saint Louis River, Minn............ 48

 Wisconsin valley ................... 32

 on Thunder Bay, Lake Superior....... 48

 quartzites, Genesis of...............'... 48

 rockSj Enlargement of quartz fragments in.............................. 23

 sandstone, Mount Whittlesey......... 3B

Iddings on enlargements of quartz fragments in ............................... 13

Indurations of sandstones by chalcedonic

silica........................... 18

 by enlargement of quartz fragments ........................... 13-17

 by independently crystallized

quartz.......................... 17

_ _ _ by weathering..............12,13,16,42,49

Keweenaw Point, Greywacke of......... 20

 Series, Greywacke of.................. 38

 sandstones, Quartz enlargements in ... 38

 , Feldspar enlargements in .......... 44-47

Kingfisher Lake, Greywackes of......... 37

Knife Falls, Minn., Clay slate of......... 32

 , Lake, Minn., Slates of ........ 1... 20,37

Lancaster, Wis., Crystallized sandstone of 15,41 

Little Iron River, Mich., Sandstone of... 38 

Localities, List of, for rocks showing 

quartz enlargements................... 23-43

Logan, Sir W., on the Huronian ..... 19,23-27,50

Madison, Wis., Crystallized sandstone of. 15 

Mahtomah, Minn., Clay slate of.......... 32

Marquette, Mich., Gannister of........... 17,28

 , , Quartzite of....................16,17,27,28

 , , Quartz-schist of................... 17,29

 , , Sandstone of ...................... 41

 region, Cherty rocks of................ 20

 , Huronian of........................ 48

 , Mica-schist of ..................21,22,30,31

Marshall Hill, Wis., Slates of ............ 20

McDonald township, Canada, Quartzite 

of...................................... 25

McLennan's Landing, Lake Huron, Qnartzite of................................... 17,24

Menominee Region, Huronian of......... 48

 , Mica-schist of ...............20,21,22, 30,31

Metamorphism in Huronian..............19,49,50

 , Mineral enlargement in............... 51

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INDEX. 55

v Page. 

Mica-schist, Enlargement of quartz frag- .

ments in.........................21,30,31

 of Marquette region ............. 21,22,30,31

 Penokee region................... 21,31

Michigamme District, Mich., Mica-schist 

of......................................21, 30,31

Microscopic rock descriptions............ 23-43

Middleton, Wis., Sandstone of........... 40

Mineral Enlargements, Bonney on........13,51-52

 , in metamorphism .... ...I........... 51

Minnesota, southern; Huronian -of....... 48

 , , Quartzitesof...................... 16,34

Monnd Creek, Minn., Quartzite of......-.. 35

Mountain Lake, Minn., Greywacke of.... 37

Murray on the original Huronian ........ 50

National Boundary, Schists of............ 37

Naumann on crystallized sandstones..... 12

Neebish Island, Quartzite of............. 16

New Lisbon, Wis., Crystallized sandstone of................................ 15

New Ulm, Minn., Quartzite of........... 35

Nipigon Bay, Sandstone of............... 39

Nonesuch Belt, Greywacke of............ 20

 mine, Sandstone of.................... 38

" Old Eed," Crystallized sandstone of.... ' 11

Ontonagon Kiver, Mich., Sandstone of... 40 

Oolite, Crystallized sandstone of......... 11

Orthoclase fragments, Enlargements of.. 45 

Packwaukee, Wis., Sandstone of......... 16,40

Palladreau Islands, Lake Huron, Greywacke of............................... 26

Palmer Mine, Mich., Quartzite of... .... 29

Partridge Falls, Minn., Greywacke of.... 37

Penokee region, Crystallized sandstone

of.....................,".......... 15,32

 , Chertyrocka of.................... 20

 , Greywackes of..................... 20

 , Huronian of........................ 48

 , Mica-schist of...................... 21,31

 , Quartzitesof....................... 30,31

 , Quartz-schists of................... 31

Pigeon Point, Lake Superior, Quartzite of 36 

Plagioclase fragments, Enlargements of . 46 

Pokegama Falls, Minn., Quartzite of..... 48

Portage Bay Island, Sandstone of........ 16,36

Portage Lake, Michigan, Sandstone of... 38 

Potsdam Sandstone, Crystallized sands

of.......................... 12,15,16,18,40

 , Cherty sandstone of ............... 21

 , Enlargements of quartz fragments

in................................ 39,40

 , Induration in, by weathering ...... 12

Prairie Eiver Falls, Minn., Quartzite of..17,18,35 

Presqu' Isle River, Mich., Sandstone of.. 39 

Qnartzite of Bad Eiver, Wis ............. 31

 Baraboo region, Wis................ 33

 Brace Mine Bay, Lake Huron ...... 28

 Caledonia, Wis ..................... 33

 Campement d'Ours, Lake Huron ... 24

 Champion Mine, Mich.............. 17

 Dakota (southeast) ................. 34

 Delton, Minn....................... 35

 Diamond Peak, Nevada ............ 43

 East Neebish Island, Canada....... 25

Quartzite of Echo Eiver, Canada ....... 25,26

 Eureka, Nevada.................... .42

 Freedom, Wis...................... 33

 Marqnette, Mich.................16,17,27,28

 T- Minnesota (southern)............... 16,34

 McDonald township, Canada........ 25

 McLennan's Landing, Canada....... 17,24,

 Mound Creek, Minn ................ . 35

 Neebish Island, Canada............. 16

 New trim, Minn .................... 35

 Palmer Mine, Mich ................. 29

 Penokee region, Wis ............... 30,31

 Pigeon Point, Minn................. 36

 Portage Bay Island, Minn .......... 16,36

 Prairie Eiver Falls, Minn...........17,18,35

 Bedstone, Minn..................... 16,34

Quartzites, Enlargements of quartz fragments in.. 16-18, 25, 26,27-29, 30, 31, 33, 34, 35,36

 Hnronian, Genesis of.................. 48

 near Thessalon Point, L. S............ 23

 of Animikie Series ....................16, 35,48

 north shore of Lake Huron.......... 24

 TealLake, Mich.................... ' 28

 Wauswaugoning Bay, Wis.......... 36

 .Origin of.............................. 12

 , vitreous, Enlargement of quartz fragments in .16-18,23-26,27-29,30, 31,33, 34,35,36 

Quartz-schist, Enlargement of quartz fragments in ................... 25,26,29,31,33

 of Ableman's, Wis.................. 33

 Baraboo region................... 33

 Marquette.Mich................. 17,29

 Penokee region, Wis............. 31

Bedstone, Minn., Crystallized sandstone

of................................ 15,35

 , Qnartzite of........................ 16,34

EocheE'crit, Wis., Crystallized sandstone 

of...................................... 15,40

Bockland, Mich., Sandstone of ........... 41

Eovo Lake, Minn., Greywacke of......... 36

Saginaw Mine, Mich., Quartzite of........ 29

Saint Joseph Island, Lake Huron, Quartzite of........................ 26

Saint Louis Kiver, Minn., Greywacke of. 32

 , Huronian of.................. 48

 , Slates of.......................20,32,48

Saint Peter's Sandstone, Crystallized sand

of..............................12,15,42

 , at Arlington, Wis ............... 42

 , Induration of, by weathering..: .12,15,42 

Sandstone, '' Crystallized ".. 11,12,13,14,16,26,32,

35, 38,40,41,42

 Daubr6e on......................... 12

 of Arlington, Wis................... 42

 of East Neebish Island ............. 15,26

 o? Southern Wisconsin.............. 15

 ofVosges.............. ............ 12

 , loose, Enlargements of quartz fragments in...................... -11,13-16,23, 35

Sandstone of Arlington, Wis .....---;.... '42

 Baraboo, Wis ....................... ' 40

 Basswood Island, Wis ............... 41

 Black Bay, Lake Superior.......... 39

 Black Kiver Falls, Wis ............. 16,40:

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56 INDEX.

Page.

Sandstone of Colorado CaHon............. 39

 . Courtlandt, Minn ................... 43

 Dakota (southeast) ................. 34

 Devil'sLake,Wis... ............... 15,34

 Delton, Minn ...................'.... 35

 Eagle Harbor, Mich ................38,44-47

 Freedom, Wis ...................... 33

 Gibraltar Bluff, Wis ................ 16,42

 GrandEapids, Wis ................. 16

 Henry Mountains, TJtah ..........'.. 43

 Lancaster, Wis ..................... 15,4.1

 Little Iron Eiver, Mich............. 38

 Madison, Wis....................... 15

 Middletoa, Wis..................... 40

 Marquette, Mich ................... 41

 Nipigon Bay, Lake Superior........ 39

 Nonesuch Mine, Mich............... 38

 Oolite in England................... 11

 "Old Bed "in England ............. 11

 Ontonagon River ................... 40

 Packwaukee, Wis .................. 16,40

 Penskee Gap, Wis.................. 15,32

 Portage Bay Island, Minn .......... 16,36

 Portage Lake, Mich................. 38

 Presqu' Isle Eiver, Mich............ 39

 Silver Islet Landing, Lake Superior. 39

 Trinidad, W.I...................... 12

Silica. Chalcedonic, as indurating material..................................... 18

Silver Islet Landing, Sandstone of ....... 39

Slate, Greywacke. See Greywacke...... 39

Slate of Knife Falls, Minn............... 32

 Lake,Minn ...................... 20,37

 Marshall Hill, Wia.................. 20

Sorby on crystallized sandstones......... 11

 Enlargement of quartz fragments .. 11

 Gannister of Yorkshire............. 11,14

 Genesis of qnartzites............... 11-22

Page. 

Sorby on quartzite of Trinidad........... 12

 Vosges sandstone................... 12

Spurr Mountain, Mich., Sandstone of... .14,15,30

Teal Lake, Mich., Quartzite of........... 28

Thessalon Point, Lake Huron, Quartzites 

near ................................... 23

Thunder Bay, Lake Superior, Animikie

of.........................-.20,35,37

 , Huronian on..................

Trinidad, W.I...........................

Tyler's Foi-k, Wis., Qnartzite of..........

 , Greywacke of ....................

Von Cotta on crystallized sandstones ....

Vosges, Crystallized sandstone of ........

Wadsworth, M. E., on induration by 

weathering ........................

 , on the Torch Lake sandstone ......

WauswaugoningBay, Minn., Qnartzite of.

48

12

30

32

12

12

13 

41 

36

Weathering of sandstones, induration by. 12,13,16,

42,49

 , Geikieon........................ 13

Western sand stone of Lake Superior, Enlargements of quartz fragments in...... 41

Westfleld, Wis., Sandstone of............ 18

 , Quartzite of........................ 33

White Pine Shale, Enlargement of quartz

fragments in ........................... 42

Whittlesey, Mount, Huronian sandstone

of...................................... 32

Winchell, N. H.......................... 17

Wisconsin Valley, Tipper, Enlargements

in slates of............................. 20

 Cherty rocks of............. 20

 Huronian of......................... 48

Young, A. A., on crystallized sand in the 

Potsdam sandstone..................... 12

Yorkshire, Gannister of.................. 11,14

Zirkel on crystallized sandstones......... 12

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