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UNITED STATES DEPARTMENT OF THE INTERIOR

OCCURRENCE OF MANGANESE

IN EASTERN AROOSTOOK COUNTY

MAINE

GEOLOGICAL SURVEY BULLETIN 940-E

-c

UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

Bulletin 940-E

OCCURRENCE OF MANGANESE 

IN EASTERN AROOSTOOK COUNTY, MAINE

BY

WALTER S. WHITE

Strategic Minerals Investigations, 1943 

(Pages 125-161)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1943

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington, D. C.

Price 25 cents

CONTENTS

Page

Abstract................................................ 125

Introduction............................................ 126

Geology of the manganese deposits....................... 128

Presque Isle area................................... 128

General geology................................. 128

Manganese deposits.......o...................... 130

Deposits associated with hematltic shale.... 132

Deposits associated with chlorite-carbonate

rock...................................... 135

Houlton area............ f ........................... 137

General geology................................. 137

Manganese deposits.............................. 138

Origin of the manganese deposits........................ 142

Depth of oxidation and enrichment....................... 144

Reserves of manganese-bearing rock...................... 146

Economic possibilities of the deposits.................. 150

Future exploration...................................... 152

Description of deposits................................. 153

Presque Isle area.................................... 153

Higgins farm.................................... 153

Dudley farm..................................... 154

Turner road..................................... 155

Castle Hill Grange Hall......................... 155

Gelot Hill...................................... .156

Capitol Hill.................................... 156

Deposit north of Perham......................... 157

Perham village.................................. 158

Frenchville..................................... 158

Other deposits in the Presque Isle area......... 158

Houlton area........................................ 159

Henderson Hill.................................. 159

Westford Hill................................... 160

Daggett Hill.................................... 160

Linneus township................................ 160

Other deposits in the Houlton area.............. 161

Township C, Range 2................................... 161

III
ILLUSTRATIONS

Page

Plate 24. Reconnaissance geologic map and sections of 

the Presque Isle area, Aroostook County, 

Maine...................................... 128

25. Geologic map of manganlferous heraatitic

shale locality in southeast Castle Hill 

township.................................. 132

26. Distribution of manganiferous hematitlc

shale in the southern half of the Houlton 

quadrangle, Maine......................... 140

27. Outcrop map of an area on the south side of

Westford Hill............................. 140

28. Geologic map of Westford Hill area, Hodgdon,

'Maine.................................. 1.. 160

Figure 14. Index map of Maine showing location of

Presque Isle and Houlton areas............ 126

TABLES

Page 

Table 5. Estimated reserves at larger deposits to a

depth of 10 feet.......................... 147

6. Partial analyses of surface samples of manganiferous rocks of Aroostook County, 

Maine..................................... 151

IV
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY BULLETIN 940 PLATE 24

Mapleton sandstone SWEDEN

New Sweden PO Chapman sandstone

New Sweden *

X x x /r^/JK

(Ga/careous tuff ancf breccia)

(Ashland limestone and shale or

former reports. S su, upper member,

calcareous shale with lenses of limestone conglomerate: SsI, lower member, gray shale localfy altered to slate)

(S a u; upper member, nubbylimt 

Sam. middle member, ribbon lit

stone: Sal, slate and calcareous s/ate)

(Sheridan sandstone of

former reports)

Undirferentiated argillites

Manganiferoushernatitic shale 

(Sofia lines give location of outcrops)

Manganiferous / / < , 

-, / // j

green shale 

(Solid lines give location of outcrops)

Inferred fault

1-9 

Localities described in text

<>Staie Rogfcl^^1;

v/:/::-:-P°v:.; /.{.v.: .: :- CAST 

.".'.'.'.'x

Base from Geological Survey 

quadrangles

68 15 68 Geology by WS.White 

and RE.Cloud,Jr.

0 *o 

(0

>1 g

T^

Sea level- Ss /* 

 -O'u

o

0

to 

3^_^SaL_Sal sam Sau Ssl i ^^iSsl |

\\ ill 1/nl d \ ^J *\V***\\^-J W '/f yt'/t // \ i \ I

0

5V)

Sau ______ Sam ^

^~\ / /'Sal

Sea level -

Ou

/

Sal

/

Ssu Sau Ssl

\ Ssl / \ 

\ / \

^-^ V

Ssu j Dm

\ ^i Ssl^r x \ Ssti ' *Ssl

\ V \ x. *J»" j 1

Sau ^ ^"im

; / sal

Pyle 

Mtn.

Area not mapped, includes 

some igneous rocks

Ssl Ssu Ssl Ssu Dv mPC

s

DC Ssu Sau

5 Miles 

j

RECONNAISSANCE GEOLOGIC MAP AND SECTIONS OF THE PRESQUE ISLE AREA, AROOSTOOK COUNTY, MAINE
GEOLOGICAL SURVEY BULLETIN 940 PLATE 25

EXPLANATION

Manj^aniferous hematitic shale

Red and green shale, locally

calcareous to west

Impure crfnoidal limestone

Impure nodular limestone

Fossil if erous limestone breccia

fc 4

Ends of trench (Manganese Ore Co.) 

Ends of trench (state of Maine^ /94l)

Test shaft (Manganese Ore Co)

_~ .JHI M __ ___

Strike and dip of beds

Strike of vertical beds

500 Feet

Geology by W. S.White, P. E.Cloud, Jr., and G. H. 

F_spenshade ; August I94I ; revised October 1942

GEOLOGIC MAP OF MANGANIFEROUS HEMATITIC SHALE LOCALITY IN 

SOUTHEAST CASTLE HILL TOWNSHIP
GEOLOGICAL SURVEY BULLETIN 940 PLATE 26

EXPLANATION

Base map from U.S.Geological Survey

67°50'

2 Miles

Geology by W.S.White and RE.CIoud,Jr.

Green and gray phyllite,poorly

bedded,locally calcareous.May

include some Ordovician phyllite

Green and gray phyllite with

minor manganiferous hematitic

Massive bedded micaceous

Black graptolit/c slate 

Fault,dashed where inferred

Boundary of areas mapped

10-14- 

Localities described in text

DISTRIBUTION OF MANGANIFEROUS HEMATITIC SHALE IN SOUTHERN HALF OF HOULTON QUADRANGLE, MAINE
By Walter S. White

ABSTRACT

Manganiferous rocks are found in two areas in eastern 

Aroostook County, Maine, one west and northwest of Presque 

Isle and the other south of Houlton. The manganiferous deposits are sedimentary lenses, up to 150 feet thick and half a 

mile long, in middle Silurian argilllte. The rocks of both 

areas are much deformed, but the deformation is less intense 

and the continuity of the deposits therefore greater in the 

Presque Isle area than in the Houlton area. The dip of the 

rocks at most deposits is steep to vertical.

Below the zone of oxidation the manganese occurs as carbonate and as the silicates braunite and bementite. These 

minerals are primary constituents of the shales and should 

continue downward to the limits of the sedimentary units that 

contain them. One deposit, which has been explored by drilling to an average depth of 130 feet, contains about 11 percent 

of manganese, but most of the deposits probably contain between 6.5 and 9 percent. There are many millions of tons of 

these manganiferOus shales in the county. Some of the deposits contain 20 percent or more of iron., mostly as hematite and 

limonite, and magnetite is abundant in the Houlton area.

In parts of the deposits above the water table about 30 

percent of the manganese occurs as a heavy stain of secondary 

oxides along joints and parting planes. . The manganese oxides 

partly replace the primary rock minerals for a distance of 1 

to 3 millimeters from cracks in the rock. At the one deposit 

from which drilling data are available, manganese oxides are 

found on only a few fractures below the water table, which is 

at a depth of 20 feet, and none were seen in rocks from below 

45 feet. It is estimated that there may be over 1,700,000 

tons of partly oxidized manganiferous shale in the region.

Some of the deposits are overlain by a thin zone, probably 

about a foot thick, that is richer in manganese than the 

underlying oxidized rocks. At the deposit explored by drilling, the average manganese content of the deposit as a whole 

is 76.4 percent of the average as determined from surface samples. The surface enrichment is believed to have taken place 

before the last advance of the Pleistocene ice, which may have 

scraped off the enriched part of many deposits. There are 

probably less than 100,000 tons of enriched rock in all the 

scattered deposits of the region.

There is a very much greater tonnage of low-grade unenriched manganlferous rock in Aroostook County, but it cannot 

be utilized until methods of extraction have been improved.

125
126 STRATEGIC MINERALS INVESTIGATIONS, 1943

INTRODUCTION

Manganiferous rocks occur in two areas In Aroostook County, 

in northeastern Maine (see fig. 14). One of these areas lies 

west and north of Presque Isle (pi. 24) and the second south

Figure 14. Index map of Maine showing location of Presque Isle and

Houlton areas.
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 127

of Houlton (pi. 26). No manganese-bearing material has yet 

been mined, but two deposits near Presque Isle have been 

partly explored by diamond drilling. The nature and size of 

the other deposits can be inferred only from small natural 

exposures and shallow trenches. Most of the manganese localities described were originally discovered by Mr. Olof Nylander 

of Caribou and Mr. Harry Thwaites of Hodgdon.

During the summer of 1941 these areas wera partly mapped 

by the writer and Preston E. Cloud, Jr., under the direction 

of Josiah Bridge. At the same time Mr. Paul F. Eckstorm was 

employed by the State of Maine to trench and sample all the 

larger deposits and many of the smaller ones. The trenching 

and prospecting done by Mr. Eckstorm were of great assistance 

to the work of the Geological Survey, and the State of Maine 

has generously permitted publication of its results.

In the fall of 1942 the Manganese Ore Co. began exploratory diamond drilling on two deposits, one in Castle Hill 

township and another in Mapleton. The writer made two brief 

visits to the area at that time, and the subsurface data made 

available by drilling have been incorporated in this report. 

He is deeply indebted to Mr. A. E. Walker, geologist in charge 

of the exploratory work, for much valuable material and information.

Valued help has been given by several members of the Geological .Survey. Preston E. Cloud, Jr., and Josiah Bridge performed much of the field work xipon which this report is based. 

T. A. Hendricks has aided materially in appraising the economic possibilities of the deposits, and the writer has profited from discussions of the geologic problems with D. P. 

Hewett and G. P. Loughlin. H. G. Perguson, P. C. Calkins, and 

D. P. Hewett have reviewed the manuscript critically. The 

petrography of the manganese in several specimens from drill 

cores was studied by Charles Milton. J. Axelrod made X-ray
128 STRATEGIC MINERALS INVESTIGATIONS, 1943

examinations of two minerals, and K.. J. Murata made a spectrographic analysis of a mineral specimen.

GEOLOGY OF THE MANGANESE DEPOSITS

Presque Isle area

General geology

The sedimentary deposits of the Presque Isle area (pi. 24) 

range in age from Ordovician to Upper Devonian. The sequence 

of the formations and their lithologic features are summarized 

in the stratigraphic table on the following page.

The thickness of the middle Silurian rocks as given in the 

stratigraphic table appears excessively large. The figures in 

the table represent measurements made in cross sections, without allowance for thickening or thinning by minor folding and 

faulting, and may be two or three times the true thickness. 

Exposures are not adequate, however, to serve as a basis for 

reliable correction factors. A second reason for the excessive apparent thickness may be the erroneous separation of 

different sedimentary facies of the same stratigraphic units. 

Specifically, it is possible that the rocks mapped as the lowest member of the Aroostook limestone actually are equivalent 

to the shales above the Aroostook. The succession of formations presented in the table is based on the simplest interpretation of the stratigraphy and structure in the light of 

what is known at the present time, but more detailed field 

work might show the need of revising this interpretation.

West and south of Presque Isle there is an igneous complex 

made up of many small, narrow, subparallel intrusive bodies of 

andesite, trachyte, and quartz trachyte porphyries. Most of 

the contacts between rock units trend north to northwest.

The sedimentary rocks are much folded and faulted (see 

structure sections, pi. 24) but the deformation is not
129

Sequence and character of the rocks in the Presque Isle area

Age

fc OJ 

<O -H

ft O

D >

P

Sn Oi

5 C

S£0) P

acd

 H

3

 rH

ID

H d -d

E

c

cd

<» -H 

H 0

 d -H -d >

 H O

O

Formation

Mapleton sandstone.

Lithology

Upper 500 feet are red and

greenish sandstone, the

remainder red conglomerate

and sandstone.

Chapman sandstone .

\Tf\ T f* O Y\ "1 f* Q

Shale and.

slate. i/

Aroostook

limestone.

Sandstone =/. . .

Mn

Greenish sandstone, Becraft

or Oriskany fauna.

Calcareous tuffs and breccias, New Scotland fauna.

- Slight unconformity 

Upper member blue and gray

calcareoxis shale with limestone lenses; lower member

greenish argillite with

thin calcareous layers .

Upper member gray, nubbly argillaceous limestone; middle member ribbon limestone; lower member slate,

partly calcareous.

Sands ton'e and conglomerate

with a little slate and

calcareous argillite.

'ked angular unconformity 

Undifferentiated gray-blue calcareous siltstone, greenish argillite, black shale,

and chert. ' [ hree fossil zones recognized.

Apparent 

thickness 

(feet)

1,800-2,500

.Over 700

2,000

5,000±

18,000±

5,000±

Unknown

I/ Ashland shale and Ashland limestone of Williams and Gregory (Williams, H. S., and Gregory, H. E., Contributions to the geology of Maine: 

rJ. S. Geol. Survey Bull. 165, 1900).

2/ Sheridan sandstone of Williams and Gregory (Williams, H. S., end 

Gregory, H. E., op. cit.).

uniformly intense. Structural differences caused by differences in lithologic character can be recognized between the 

northern and southern parts of the Presque Isle area. South 

of the Aroostook River, where massive sandstones are involved 

in the deformation, the folds are open and plunge at low angles. The axis of a broad syncline trending north-south lies 

halfway between Mapleton and Presque Isle, and farther west 

are a narrow anticline and syncline of similar trend. These 

folds plunge to the south except in the area underlain by the

N

555112 O - 43 - 2
130 STRATEGIC MINERALS INVESTIGATIONS, 1943

Mapleton sandstone, which lies unconformably upon the older 

rocks in a structural basin. North of the Aroostook River, 

and in eastern Castle Hill township south of the river, the 

rocks are dominantly argillites and thin-bedded limestones. 

The bedding dips steeply and folds are prevailingly small. 

Nearly isoclinal folds several hundred feet across were found

;

at many places in the lower,, argillaceous member of the Aroostook limestone between New Sweden and the Aroostook River, but 

such folds are difficult to identify except where their noses 

are exposed. Minor folds, less than 10 feet from crest to 

crest, are rare except in the middle Silurian ribbon limestone 

and the manganiferous shales. Large and small folds alike 

plunge steeply both to the north-northeast and south-southwest. 

 Slaty cleavage is well developed in argillaceous rocks north 

of the village of State Road. It generally dips steeply to 

the west, and at most places its relation to bedding shows 

that the rocks lie on the east limb of an anticline.

Outcrops west of Mapleton and State Road indicate at least 

two large faults of northerly trend. Each of these faults has 

the older rocks on,the west side, and both are probably reverse faults dipping steeply to the west. Minor faults of the 

same type were found at several places, but they could be 

traced for only a few tens or hundreds of feet.

Manganese deposits

Manganiferous .rocks are found at three stratigraphic horizons in the middle Silurian series, one being in the greenish 

argillite immediately above the Aroostook limestone and two in 

the lower slate and calcareous slate member of the Araostook 

limestone (see p. 129). The distribution of outcrops of manganif erous rocks is shown in plate 24. The manganese-bearing 

rocks are well bedded and locally contorted, and the deposits 

are elongate parallel to the regional and local strikes of
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 131

bedding. The dips are consistently greater than 60/ and prevailingly almost vertical. In the higher of the two manganiferous horizons of the Aroostook limestone and in the greenish 

argillites above that formation, the manganese is intimately 

associated with red hematitic shales. The lowermost manganiferous horizon is characterized by a heavy, dark green, thinbedded chlorite-carbonate rock containing very little hematite, 

The manganiferous rocks crop out only at scattered points. 

Failure of a given deposit to crop out for a long distance 

along the strike may be due to structural complication, to 

stratigraphic lensing, or to concealment by glacial cover, 

whose average thickness at various places in Aroostook County, 

except in swamps and gravel-covered areas, ranges from 2 to 8 

feet.-^ The manganiferous shales generally crop out, however, 

in larger and higher exposures than the surrounding rocks, and 

they should therefore be exposed, if they are present, in 

areas where there are outcrops of other rocks. Where manganiferous rocks are not exposed but are;not too deeply buried, 

the soil immediately overlying them has a characteristic dark 

olive-drab or purple color and contains abundant black-stained 

shale fragments. Because of such indications, and of the 

relative thinness of the glacial cover, it is possible to 

trace zones of manganiferous rocks at many places in cultivated areas where outcrops are few or wanting. It seems reasonable, on the whole, to attribute the apparent discontinuity 

of the zones only in small part to concealment by glacial 

cover, at least within areas now under cultivation above the 

valley floors. The discontinuity is probably due mainly to 

lensing and faulting. One deposit, 2 miles west of State 

Road, is clearly cut off by a fault at the south end, and many 

other deposits may be similarly interrupted. Most deposits

I/ Hurst, L. A., Knobel, E. W., and Hendriokaon, B. M., Soil survey of 

the Aroostook area, Maine: U. S. Dept. Agr., Advance Sheets, Field operations of the Bur. of Soils, 1917, p. 19, published 1921.
132 STRATEGIC MINERALS INVESTIGATIONS, 1943

show marked differences in thickness at different points along 

the strike (pi. 25), which suggests that they are lenslike. 

If the nianganiferous zones were originally laid down as sedimentary layers that were continuous over large areas, the Tact 

would probably be apparent despite glacial cover and structural complications; it is believed, therefqre, that the manganiferous rocks were probably deposited as scattered small 

lenses.

Deposits associated with hematitic shale. The hematitic 

shale is interbedded with red, gray-green, and green argillite. The stratigraphic zones containing hematitic shale are 

commonly 5 to 30 feet thick; their greatest observed thickness 

is about 150 feet (pi. 25). Such zones contain, on an average, 

25 or 30 percent hematitic shale, and probably nowhere contain 

more than 50 percent. Individual beds' of hematitic shale, 

separated by nonhematitic shale, range in thickness from a 

fraction of an inch to about 20 feet; their average thickness 

is 1 or 2 feet.

Diamond drilling on a deposit of hematitic shale at the 

M. S. Dudley farm in Castle Hill township has made it possible 

to study the mineral composition of this type of deposit with 

the aid of unoxidized material. Specimens collected from 

several drill cores were examined petrographically by Charles 

Milton, to whom the writer is indebted for identification of 

many of the minerals in the deposit. This laboratory study 

has been supplemented by detailed assay data of the Manganese 

Ore Co. and by petrographic examinations made by the writer on 

oxidized material collected before the drilling.

The rocks are typically made up of thin layers ranging in 

thickness from a fraction of a millimeter to about 25 centimeters. The average grain size is about 0.02 millimeter. 

Each layer contains an intimate mixture of two or more minerals, and the boundaries between individual grains are generally vague.
133

The manganese minerals known to occur below the zone of 

oxidation are braunite ^(MnjFeJpOg.MnSiOg), bementite, and 

manganiferous carbonate. Some braunite has been positively 

identified, and the most abundant of the manganese minerals, 

which occurs in dense aggregates with iron oxide and calcitic 

carbonate in the heaviest hematitic layers, is believed to be 

braunite. Relatively pure braunite, Identified by X-ray 

study, occurs locally in red shale, where it forms discontinuous layers a quarter to half .an inch thick. The layers where 

Interrupted have rounded ends, and they appear, when examined 

under the microscope, to cut across the bedding of the rock. 

The microscope also reveals that the cores of some masses of 

braunite consist partly of well-crystallized bementite. The 

braunite is dark brownish-black and rather lustrous. Only a 

negligible quantity of braunite occurs in this manner, but the 

Dudley farm deposit, to judge from its average manganese content and from visual.estimates, contains 10 or 11 percent of 

what is believed to be braunite.

Bementl/te, which probably makes up 1 or 2 percent of the 

deposit, is mostly associated with carbonate in small pods or 

nodular masses and in cross-cutting veinlets. Many of the 

nodular masses contain collophanite. Bementite and some material that is probably bementite occur as disseminated particles and as irregular masses in some of the hematitic shale.

White to pink carbonate is an abimdant constituent of the 

deposits of hematitic shale. It occurs both as a sedimentary 

constituent of the rocks, generally associated with iron oxide 

or chlorite, and as veinlets and stringers that cross the bedding. Some of the veinlets follow mlcrofaults. There seems 

to be a wide range in the composition of the carbonate. Most 

of it is essentially calcite and effervesces with cold dilute 

HC1; much of it, however, gives a bead test for manganese, and 

some of it has the pink color and the optical properties of a
134 STRATEGIC MINERALS INVESTIGATIONS, 1943

carbonate close to rhodochrosite. It is estimated that possibly 2 percent of the manganese in the Dudley farm deposit is 

present as carbonate, and that about 25 percent of the deposit 

"is carbonate.

About 27 percent of the manganiferous zone at the Dudley 

farm deposit is PegOg. The red color of the rocks indicates 

that a large part of the iron occurs as hematite, but a little 

limonite is visible under the microscope. The iron oxide is a 

major constituent of some of the heaviest layers, and more or 

less of it is present in all the layers.

Apart from the carbonate, the principal nonmetallic minerals of the deposit are the silicates chlorite and sericite. 

Chlorite is intimately mixed with the other minerals in the 

hematltic beds. The interbedded red and green shales consist 

largely of sericite and chlorite and contain scattered grains 

of detrital quartz. A few heavy dark-green beds, mostly at 

the west side of the deposit, consist mainly of chlorite and 

slightly manganiferous carbonate. Biotite is present in a few 

places. Collophanite (hydrous calcium phosphate, Ca-PgOg.HgO) 

is found with carbonate and bementite in irregular areas and 

nodules, and the sludge and core from one drill hole were 

found to contain, on the average, 0.67 percent of phosphorus. 

Barite forms the inner part of the rounded bleb of greenish 

carbonate in a specimen of red shale.

A layer of volcanic ash 1 to 2 inches thick was noted at 

the Dudley farm "in one drill core and in two trenches on the 

surface. Should this ash prove to belong to a single continuous layer in the deposit, it would serve as an excellent reference plane for detailed stratigraphic and structural studies.

2/ It consists, according to Charles Milton,-'mainly of crystals

of sodic plagioclase in a matrix of what is probably montmorillonite, derived from fragments of glass. Strongly pleo2/ Personal communication.
135

chroic biotite and stubby prisms of apatite are abundant, and 

small fragments of slightly altered rhyolite can also be identified.

The manganiferous rocks and adjacent strata are strongly 

oxidized at the surface. The rocks are coated and partly 

replaced along bedding planes and joints by extremely fine 

grained black manganese oxide. Shales that are largely composed of hematite are not noticeably replaced; in them the 

manganese oxide forms mere films, readily scraped off, on 

relatively fresh rock. Rocks, however, that contain abundant 

carbonate, chlorite, or sericite are partly replaced to distances of 1 to 3 millimeters from cracks in the rock. Oxides 

are .particularly noticeable along fractures that follow carbonate veinlets. Fissile shales with closely spaced partings 

appear megascopically to be almost completely replaced, but it 

is apparent from analyses of surface rocks that, even if all 

the manganese is calculated as MnOg, manganese oxide only 

locally forms more than 40 percent of the rock. In thin sections the incompleteness of the replacement is evident. 

Within the black-stained areas along cracks there are small 

islands of unreplaced rock; quartz, in particular, is hardly 

anywhere corroded. The extent to which the braunite is oxidized is not known.

Although most of the statements in the preceding paragraphs are based solely on observations made at the Dudley 

farm deposit, this deposit is believed to be typical, qualitatively, of all the bodies of manganiferous hematitic shale in 

the Presque Isle area. There are probably differences in the 

relative proportions of certain lithologic types and mineral 

constituents, but in general the rocks exposed at the surface 

are similar at all the deposits.

Deposits associated with chlorite-carbonate rock. The 

lowest manganiferous strata, which are in the Aroostook
136

limestone, differ primarily from the others in being almost 

free from hematite. The individual manganiferous zones range 

in thickness from 5 to 50 feet and average about 15 feet. In 

a field 1.4 miles N. 26° E. of Perham there are three manganif erous zones, separated by gray serlcitic phyllite, within a 

stratigraphic interval of 140 feet, but here the aggregate 

thickness of the manganiferous rocks is only 55 feet. At this 

and a few other places it is difficult to determine whether 

two or more closely parallel streaks of manganiferous rock, 

separated by phyllite, represent different beds or a single 

bed repeated by folding or faulting.

The manganiferous rocks are made up of alternating light 

and dark green layers, and are noticeably heavier and harder 

than the typical shales of the area. The layers range in 

thickness"from a fraction of a millimeter to about 10 centimeters.

The lighter-green layers are largely composed of a very 

fine grained, greenish, calcitic carbonate, which effervesces 

with warm dilute HC1 and generally gives a bead test for manganese and iron. The darker layers consist largely of chlorite with small quantities of carbonate and 5 to 10 percent of 

quartz. The carbonate apparently makes up 15 to 30 percent of 

the individual manganiferous zones. In several specimens of 

shale chlorite is oriented parallel to the axial planes of 

small folds. Three or four hematitic layers a few millimeters 

thick were found at two deposits.

The rocks are stained at the surface with black manganese 

oxide, but in general the stain is not so dark as in the hematitic shales. There are fewer cracks and closely spaced bedding planes than in the hematitic shales, and consequently the 

amount of replacement by manganese oxide is less. The rock is 

partly replaced for as much as 3 millimeters from cracks in
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 137

the carbonate layers but generally for not more than a millimeter in the chloritic layers.

Houlton area / 

General geology

In the Houlton area (pi. 26) geologic mapping was limited 

to the immediate vicinity of localities at which manganiferous 

rocks have been reported. The rocks in the small areas mapped 

are mostly green and gray phyllites and quartzitic phyllites, 

probably of Silurian age. Black graptolitic slate of Ordovician age was found at three places, but its relation to the 

Silurian rocks was not established. The manganiferous rocks 

are everywhere interbedded with gray phyllite, and at Westford 

Hill they occur a short distance stratigraphically below a 

thick series of quartzitic phyllite beds.

The structure is complex, and its character is perhaps 

most graphically illustrated by the detailed map of Westford 

Hill and vicinity (pi. 28), an area of better than average 

exposure. In this area the major folds strike northwestward, 

plunge steeply to the east or southeast, and are slightly 

overturned toward .the southwest. Most of the dips recorded 

are to the northeast and steeper than 70°. These folds are 

cut by a set of faults, which strike north to northwest and 

seem to be reverse faults dipping steeply eastward. Along a 

later northeast-trending tear fault, of unknown dip, the north 

side seems to have moved relatively eastward about 1,200 feet. 

All the rocks have a .well-developed fracture cleavage, which 

is generally vertical and strikes north to northeast. At many 

places the cleavage crosses the axial planes of major and 

minor folds at a high angle, and it is therefore believed to 

be younger than the folding.

The structure in other parts of the Houlton area is probably of the same type as that in the vicinity of Westford Hill. 

555112 O - 43 - 3
138 . STRATEGIC MINERALS INVESTIGATIONS, 1943

In the east-central part of the Houlton area, the distribution 

of outcrops suggests that a single bed of phyllite containing 

manganiferous rock extends from the Canadian border almost to 

Westford Hill. The folds mapped in this belt (pi. 26) are 

largely Inferred, and the boundary lines of the belt have been 

drawn in such a way as to include over a hundred small outcrops of manganiferous rocks and no large areas of nonmanganiferous rocks. The strike of the bedding at most places here 

Is slightly east of north. The outcrop areas mapped are 

largely on hills, and the lower parts of the valleys contain 

few, if any, exposures.

Manganese deposits

The manganiferous rocks of the Houlton area are interbedded with gray Silurian phyllite. The phyllite is not generally well stratified, and Its total thickness in the Houlton 

area is not known, but the part of it that contains all the 

manganiferous strata is about 300 to 1,000 feet in thickness. 

Between the stratigraphic limits of the highest and lowest 

manganiferous beds there may be many manganiferous zones, separated from one another by zones of barren phyllite. Because 

of the Irregular interbedding, however, the manganiferous 

zones must be defined arbitrarily. Beds of manganiferous rock 

without interbedded phyllite may locally be as much as 12 feet 

thick, but thicker stratigraphic units contain larger percentages of barren rock. One large outcrop on the south side of 

Westford Hill (pi. 27) reveals a manganiferous zone 35 feet 

thick containing about 35 percent of phyllite, which is 

stained with oxides. On the west end of a hill 2 miles northeast of Linneus, a manganiferous zone 53 feet thick is 55 percent phyllite, partly stained. On Henderson Hill, 3^- miles 

southeast of Houlton, a zone 107 feet thick contains about 65 

percent of phyllite, mostly stained. Stratigraphic units over
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE ' 139

300 feet thick probably nowhere contain more than 15 percent 

of manganiferous rock.

The manganiferous beds can be traced only for short distances along the strike, as may be seen in an outcrop map of 

an area with better than average exposures (see pi. 27). In 

general the exposures of bedrock are more extensive in the 

Houlton area than in the Presque Isle area, and if the manganife-rous beds were continuous for distances of several hundred 

feet the fact should be readily apparent. The beds are much 

folded and faulted on a small scale, and the discontinuities 

along the strike are believed to be due in the main to faulting and folding, though some of.them are probably due to 

stratigraphic lensing. Projection of bodies more than 50 feet 

along the strike from trenches or exposures is hazardous, and 

even where exposures are good few of the deposits can be 

traced for more than 250 feet along the strike. As the dip of 

the bedding and the plunge of the folds are generally steep, 

vertical discontinuity of the same order of magnitude as the 

horizontal can be expected.

The manganiferous rocks are typically made up 'of layers 

ranging in thickness from a fraction of a millimeter to about 

30 centimeters. Each layer contains an intimate mixture of 

two or more minerals. The average grain size of different 

rocks ranges between 0.02 and 0.1 millimeter, but in places 

there are crystals of magnetite more than a millimeter across.

In the unoxidized rocks, manganese occurs as carbonate and 

as a mineral that is probably bementite. Possibly some manganese is present also in an opaque mineral such as braunite or 

hausmannite, but the metallic minerals were not studied in 

detail in polished secions or by chemical or X-ray methods. A 

specimen of manganiferous rock collected by G. P. Loughlln on 

Westford Hill was found by W. T. Schaller to contain magnetite 

and hematite, but apparently all the manganese was in rhodo-
140 STRATEGIC MINERALS INVESTIGATIONS, 1943

chrosite. Autoradiographs of two specimens collected by the 

writer from the Houlton area were made at the Massachusetts 

Institute of Technology under the direction of Dr. C. Goodman. 

The 'manganese, made radioactive in a cyclotron, appears white 

in prints made from a photographic plate exposed to the 

treated surface. All the manganese appears to be in those 

parts of the specimens that contain carbonate; areas occupied 

by sericite, chlorite, and opaque minerals are dark in the 

prints. It thus appears that a larger proportion of the manganese is present as carbonate in the rocks of the Houlton 

area than in the hematitic shales of the Presque Isle area.

White carbonate occurs in layers, nodules, and veinlets. 

The layers contain carbonate mixed with chlorite in different 

proportions, and some layers also contain sericite, quartz, 

and fine-grained disseminated magnetite. Nodules of manganiferous carbonate appear in thin section as round or-oval 

patches up to 5 millimeters across, generally with sharp 

boundaries against the enclosing chlorite-sericlte schist. 

Most of the nodules -are pure carbonate, but the grain size in 

different nodules may be markedly different, even in the same 

specimen. In the nodules of one specimen, the carbonate has a 

radial-fibrous habit. The cores of manganiferous carbonate 

nodules in another specimen contained an unidentified black, 

opaque material, possibly secondary manganese oxide. An 

uncommon type of banded nodule seen in one thin section has a 

quartz rim surrounding a core composed of chlorite and rhombohedral crystals of carbonate. Carbonate veinlets, mostly less 

than a millimeter wide, are abundant in all the manganiferous 

rocks. Many are parallel to the banding of the rocks, but the 

majority are cross-cutting.

The carbonate is not uniform in composition. Some of it 

has refractive indices near those of rhodochrosite. Most of 

it effervesces weakly with cold dilute HC1 but is shown by
GEOLOGICAL SURVEY BULLETIN 940 PLATK

25 0

I I

125 Feet

EXPLANATION

*"^

Hematitic shale beds, mostly

with heavy manganese stain

Shale, with heavy manganese 

Stain, but little or no hematite

Gray and green phyllite 

Red slate bed

Fault

F =1 

Ends of trench

Note: Strike of bedding indicated by lines of lithologic 

patterns. Dips steep northeast 

to vertical

OUTCROP MAP OF AREA ON SOUTH SIDE OP WESTFORD HILL 

(LOCATION OF AREA SHOWN AT "A" ON PLATE 28)
MANGANESE IN EASTERN AROOSTOOK,COUNTY, MAINE 141 

many bead tests and the two autoradiographs mentioned above to 

be manganiferous. Without analyses of samples taken from manganiferous zones below the zone of oxidation, it is difficult 

to estimate either the average percentage of carbonate in the 

rock or the average manganese content of the carbonate. 

Allowing for enrichment in surface samples (see p. 144), .and 

assuming that about 2 percent of the manganese is present in 

bementite and none in other minerals, the writer has estimated 

that the deposits contain, on the average, from 3 to 6 percent 

manganese as carbonate.

A mineral that is probably bementite is found in moderate 

quantity not only in some of the distinctly manganiferous 

rocks but locally in the interbedded phyllites. The mineral 

is reddish-brown in thin section, its birefringence is low, 

and its refractive indices are slightly below 1.65. It forms 

separate rounded grains up to 0.1 millimeter across, mostly 

scattered through chloritic layers, which may or may not contain sericite and specular hematite. In oxidized specimens 

the mineral is replaced by black opaque material, probably 

manganese oxide. How much of the supposed bementite there is 

in the manganiferous rock cannot be accurately estimated from 

a fevy thin sections of oxidized material, but there may be as 

much as 5 percent in some deposits.

It is estimated from the analyses of surface samples collected by Mr. Eckstorm that magnetite and specular hematite 

together make up, on the average, about 26 percent of the rock 

in the manganese deposits of the HoUlton area. Both minerals 

occur more or less abundantly as fine-grained aggregates in 

certain layers, and crystals of magnetite are scattered 

through many of the chloritic and sericitic layers. There is 

probably more magnetite than hematite.

Chlorite and sericite are the principal nomnetallic minerals other than carbonate. They are abundant in the
142 STRATEGIC MINERALS INVESTIGATIONS, 1943

manganiferous strata and are the chief constituents of the 

interbedded phyllites. The chloritic and sericitic layers 

contain 10 or 15 percent of quartz. Hornblende was observed 

in one specimen of manganiferous rock, but no biotite was 

seen. Some outcrops contain a little pyrite. About 0.6 percent of phosphorus is present in the rocks, probably as apatite.

Secondary manganese oxides have the same mode of occurrence in the Houlton area as in the Presque Isle area, and 

they need not be further described. Locally there seems to be 

extensive replacement of phyllites by oxides; small fragments 

of phyllite are black to the core and appear on superficial 

inspection to be completely replaced, but under the microscope 

they generally show miich unreplaced quartz, sericite, and 

chlorite.

ORIGIN OF THE MANGANESE DEPOSITS

The manganiferous rocks of Aroostook County were deposited 

as marine strata in middle Silurian time. The deposits at the 

Dudley farm and in Mapleton are closely associated with fossiliferous marine limestone and shale. Well-preserved graptolites were found in phyllite only a few feet from manganiferous beds on Westford Hill (pi. 28). The abundance of carbonate, the absence of coarse detrital material, and the 

regional distribution of the enclosing formations suggest that 

the beds were laid down as geosynclinal sediments at a considerable distance from shore. A lenticular bed of fosslliferous 

limestone conglomerate, about 200 feet stratigraphically above 

the Dudley farm deposit, was probably derived from the breaking up of a nearby reeflike structure and indicates that the 

sea was relatively shallow.

tie fflftagftftifWOua strata were probably deposited as discontinuous layers of Irregular thickness. They are found at
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 143

what appear to be three different stratlgraphlc positions in 

the Presque Isle area, but probably at only one in the Houlton 

area. It is not possible, on the basis of available evidence, 

to determine the extent to which individual deposits were laid 

down contemporaneously with one another.

The rocks of the region have been folded, faulted, and 

mildly metamorphosed, probably during late Devonian time. The 

chief differences in mineral composition between the manganiferous rocks in the Houlton and Presque Isle areas, notably the 

presence of magnetite and specular hematite near Houlton, can 

be attributed to a slightly higher grade of regional metamorphism in the Houlton area. All the manganiferous rocks are 

cut by numerous tiny veinlets, which are believed to have been 

formed, during the deformation of the rocks, by solution and 

redeposition of carbonate already present within the limits of 

the deposits. Vein quartz and pyrite are no more abundant in 

the manganiferous rocks than in the other lithologlc units of 

the region.

The heavy stain of manganese oxides along joints and partings is clearly the result of relatively recent oxidation of 

the rocks, and appears to be related to the present water 

table. Within a few feet of the surface there has been a 

moderate enrichment of the deposits by addition of secondary 

manganese oxides, for at the Dudley farm deposit the average 

manganese content of the surface samples exceeds that of samples taken from depth to a far greater degree than would be 

expected to result solely from oxidation of manganiferous carbonates in place. In many places the enriched rocks lie below 

several feet of unoxidized till, and fragments of shale 

stained with manganese oxides can be found in till that 

appears quite fresh. It is probable, therefore, that a thin 

zone of leached rock has been stripped from the deposits by 

glacial action, and that most, if not all, of the enrichment
144 STRATEGIC MINERALS INVESTIGATIONS, 1943

took place before the last advance of the Pleistocene glaciers. On small cliffs in the Houlton area, where glacial 

plucking can be assumed to have removed more than the usual

quantity, of rock, the oxides are noticeably less abundant than

\

elsewhere. This fact suggests that here both the zone of 

leaching and the underlying zone of enrichment were removed.

DEPTH OP OXIDATION AND ENRICHMENT

At the Dudley farm deposit, the only one from which drilling data are available, the' decrease In the proportion of 

secondary oxide with depth Is readily apparent. At)OV9 the 

water table, which is approximately 20 feet below the surface, 

there is abundant oxide along joints and bedding planes. The 

percentage of the total manganese that occurs as oxide probably ranges from about 90 in highly fractured and thin-bedded 

rocks to about 10 in the most massive rocks. The average for 

the whole zone above the water table is probably about 30 percent of the total manganese, but this estimate is based only 

on a brief examination of the drill cores and may be in error 

by as much as 10 percent manganese.

The average manganese content of 'the Dudley farm deposit 

as a whole is 76.4 percent of the average manganese content of 

surface samples taken within a few inches of the top of the 

bedrock; the surface samples, in other words, are 31 percent 

richer than the average. The depth to which this enrichment 

extends can only be estimated. Recovery of core in the upper 

few feet of drill holes was poor, and, as the zone is probably 

neither well defined nor uniformly thick, the depth of enrichment cannot readily be determined by inspection. Some evidence is supplied, however, by data from 13 drill holes that 

were begun within the assay walls of the deposit. The average 

manganese content of the whole deposit is 11.1 percent. The
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 145

sludge and core above a depth of 7 feet ^/average 10.6 percent 

manganese. The average for depths of 7 to 14 feet is also 

10.6 percent, and the average from 14 to 21 feet is 12.6 percent, or 1.5 percent greater than the average for the deposit. 

These figures suggest the possibility that there has been 

slight leaching in the upper part of the zone above the water 

table and slight enrichment in the lower. It is believed, 

however, that the variations are within the limits that can be 

attributed to the wide range in composition of the primary 

rocks. The averages are sufficient to show that the zone of 

enrichment is not thick enough to increase the grade of the 

upper 7 feet to any noteworthy degree.

No sharp line of demarcation was noted between the rocks 

above and below a depth of 20 feet, but very little manganese 

oxide was seen in drill cores from below this depth. Oxides 

are found to depths of at least 55 feet below the surface, but 

they are restricted to a very few fracture planes.

No data on the depth of oxidation and enrichment are 

available for other deposits. Certain generalizations may be 

made, however, from the evidence obtained at the Dudley farm 

and from the geologic history of the deposits. Secondary manganese oxides in about the same abundance as at the Dudley 

farm deposit can be expected down to the water table. The 

depth of the water table probably differs appreciably from 

place to place; in deposits near the tops of high hills for 

example in those on Gelot and Capitol Hills in New Sweden and 

those in the Houlton area the depth to water is almost certainly greater than in the Dudley farm deposit, which lies on 

a very gentle slope near the bottom of a valley.

The thickness of the zone of enrichment may be expected to 

differ in deposits with different topographic setting. Rocks

3/ The holes were drilled at 45° to 40° from the horizontal, and samples taken from each 10 feet on the incline represent about 7 feet vertically.
146 STRATEGIC MINERALS INVESTIGATIONS, 1943

exposed on high knobby hills, particularly on the south or 

plucked sides, have probably been more severely eroded by the

Pleistocene glaciers than less-exposed deposits. If the sur-

\ 

face enrichment of the manganlferous deposits preceded the

last glacial advance, as seems probable, the enriched zone may 

well have been stripped from many deposits that were exposed 

to vigorous glacial erosion. The manganese content of surface 

samples from such deposits is .probably more representative of 

the subsurface grade than are the surface samples from the 

Dudley farm. The writer saw no deposits that appeared to be 

less eroded than the one at the Dudley farm, but if such a 

deposit exists it might have a thicker zone of enrichment or 

might even be covered by a capping of leached rock.

RESERVES OP MANGANESE-BEARING ROCK

An estimate of the reserves at the larger deposits to the 

arbitrarily chosen depth of 10 feet is presented in table 5. 

The poor exposures and lack of subsurface data prevent the 

precise delimitation of the individual deposits. Some idea of 

their size may be gained, however, from the few natural exposures, and even more from the trenches dug under the auspices 

of the State. Where trenching has removed the overburden the 

exact width of most deposits can be measured, and at a few 

places the width can be determined rather closely without 

trenching.. The length is more difficult to determine.

In giving estimates of reserves, the terms "indicated ore" 

and "inferred ore" are used in somewhat arbitrary senses. 

"Ore" signifies material that contains at least 7 percent manganese, although it is recognized that relatively small deposits of rock containing 7 percent manganese cannot at present 

be called "ore deposits" in the strict sense. Where two 

trenches are dug within a few hundred feet of each other and 

geologic conditions, such as uniform attitudes or
Table 5. Estimated reserves at larger deposits to 

Deposit

Castle Hill Grange Hall..

Gelot Hill.. .............

Capitol Hill.. ...........

Perham, north of village.

Westford Hill. . ..........

Daggett Hill .............

Length 

(feet)

100

2,100

f 800

900

100

1,200

450

f 400

[ 150

100

200

i

Average 

width 

(feet)

23

1 P 11)

30

105

40

32

115

35

95

88

^n

'Indicate

Tons

2,300

262,500

24 , 000

94,500

4,000

38,400

51,800

14,000

1 4. POO

8,800

6,000

l d ore"

Surface 

grade 

(percent 

Mn)

17.6

14.46

9.2

8.7

1 ? Q7.6

7.7

10

7.5

8.1

7.5

Probable 

grade in 

depth 

(percent 

Mn)

13

11.06

7

8

11

6.5

6.5

8

7

7

7

Len

(f

1

1

1

I/ Proved "ore" totals over 2,000,000 tons, to an average depth of 130 feet. Th

may also be minable for a greater length along the strike. All data for this deposi

by A. E. Walker of the Manganese Ore Co.
148 STRATEGIC MINERALS INVESTIGATIONS, 1943

raanganiferous float, indicate that the manganiferbua zone is ^_ 

continuous between them, the calculated tonnage of manganiferous rock is considered to be "indicated ore". Calculated 

tonnages based on projections of 50 feet from a single trench, 

or based on a short projection between a trench and a large 

outcrop are also called "indicated ore". Where the spacing of 

trenches is of the order of 1,000 feet and there is a possibility of structural or stratigraphic discontinuity or where 

projections have been made between one trench and float or 

small outcrops at some distance from it, the estimated tonnage 

is classed as "inferred ore".

The lack of subsurface data at all but one deposit makes 

it necessary to adopt an arbitrary means of representing the 

relative quantities of manganiferous rock present at the different deposits. Tonnages of indicated and inferred ore are 

calculated only to a depth of 10 feet below the overburden. 

Ten cubic feet of rock are assumed to weigh 1 ton. At most 

deposits, manganiferous rocks undoubtedly continue downward 

for many tens or hundreds of feet. The arbitrary depth of 10 

feet has no relation to the zones of oxidation and enrichment 

at the different deposits; it is used solely as a convenient 

datum for tonnage estimates, without any implication that 10 

feet is a limiting depth. The actual depth to which the manganiferous rocks might conceivably be mined at a given deposit 

might be greater or less than 10 feet, and would depend on the 

grade at depth, the method of mining, the chemical composition 

of the rocks, their structure, and possibly on other factors 

the effect of which cannot now be predicted.

The average manganese content of the surface rocks at various deposits, as presented in table 5, was calculated from 

trench samples collected by Mr. Eckst.orm. Partial analyses of 

these samples are presented in table 6.
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 149

The trenches were not all dug at right angles to the 

strike of the rocks, chiefly because it was not everywhere 

possible to determine the strike beforehand. Some of the 

trenches, indeed, reveal folds and changes of strike. In 

determining the average grade for a trench, each analysis was 

weighted according to the thickness of the stratigraphic unit 

that it represented, and the weighted averages may differ 

materially from the numerical averages of the analyses in 

table 6. Where the trench was not at right angles to the 

strike, the total length of a sampling cut may exceed the 

width of the manganlferous zone at the place where the sample 

was taken.

Because of the enrichment in the upper parts of some 

deposits, the average percentage of manganese is likely to be 

greater in channel samples taken within a few inches of the 

top of the bedrock than in those taken at greater depth. In 

addition to the estimate of the grade at the surface, therefore, it seemed advisable that where possible a rough estimate 

of the probable grade at depth be given also for each deposit. 

These estimates, given in table 5, are based on consideration 

of the topographic position of each deposit and the amount of 

staining by secondary manganese oxides observed in the field.

It should be pointed out that the surface rocks at the 

Dudley farm deposit contain 11.4 percent manganese according 

to the State of Maine's sampling, and 14.46 according to the 

Manganese Ore Co.'s sampling. For essentially the same block 

of ground as is represented by the State's samples, the Manganese Ore Co.'s samples show an average manganese content of 

14.17 percent. The samples were not taken at the same places, 

and the difference in the results] might conceivably be -due to 

any one of several geologic reaso/ns. It seems more probable, 

however, that it is due to some difference in the method of
150 STRATEGIC MINERALS INVESTIGATIONS, 1943

sampling or of determining the manganese content. Until the 

reasons for the discrepancy are known, some doubt must attach 

to all the figures for manganese content in surface samples. 

In summary, the probable reserves of manganiferous rocks 

can be roughly estimated from the data presented in table 5. 

There are many millions of tons of rock in depth that contain 

from 6.5 to 11 percent manganese, mostly in the form of carbonate and silicates. If the average depth of oxidation is 

over 20 feet, there may be over 1,700,000 tons of oxidized 

rock, also containing 6.5 to 11 percent manganese; but in this 

rock about 30 percent of the manganese may be in the form of 

secondary oxides. Lastly, if it is assumed that the average 

thickness of the zone of enrichment is 1 foot, there are about 

85,000 tons of rock in which the maximum content of manganese 

is 17.6 percent and the average content about 9 percent. Over 

50 percent of this manganese probably occurs as oxide.

ECONOMIC POSSIBILITIES OP THE DEPOSITS

The deposits of Aroostook County have, in the aggregate, 

so large a volume that they constitute a potentially important 

source of manganese. In a discussion of economic possibilities, the three categories of manganiferous rock noted in the 

summary statement of reserves should be treated separately.

The manganese in the zone of surface enrichment is more 

abundant and in a form more suitable for economic extraction 

than that in the lower parts of the deposits. The total tonnage of enriched ore, however, is probably too small to be 

worth mining by itself. The deposits are scattered over a 

large area, and probably not more than one or two of them contains enough ore to justify the construction of a mill. In 

addition, an overburden of glacial drift that averages about 

4 feet in thickness would have to be removed.
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 151

Table 6. Partial analyses of surface samples of 

manganiferous rocks of Aroostook County, Maine i

Locality

Higgins. ..........

Dudley.. ..........

Castle Hill Grange 

Hall.

Gelot Hill........

Capitol Hill......

Henderson Hill....

Westford Hill..'...

Daggett Hill......

Percent

Mn

17.6

t- 10.6 

[13.6 

8.5 

[13.0 

10.2

9.2

1

8.4 

9.6 

I 8.9 

12.2 

8.7 

8.9

16.9 

12.1 

13.3

7.6 

11.0

14.2

7.0 

16.5 

6.1 

7.8 

7.9 

i 6.3 

r 9.1 

8.6 

7.5

8.8 

10.3 

8.8 

/ 7.7 

| 7.3

7.0 

7.5

8.1

Percent 

Fe

25.4

24.0 

22.4 

23.7 

18.8 

20.1

17.6

27.3 

18.5 

29.0 

26.2 

21.8 

28.6

5.2 

18.8 

20.7

13.0 

17.3

15.3

17.4 

18.2 

15.9 

20.5 

20.4 

16.8 

19.5 

19.6 

19.4

20.8 

25.4 

18.3 

18.4 

14.6

30.7 

19.8

17.0

Percent 

P*

0.58

0.82

1.04

0.67

0.62

0.60

0.55

Percent 

S#

0.14

0.03

0.05

0.11

0.04

0.09

0.18

Percent 

insolublet

28.8

32.2 

32.0 

36.6 

35.8 

38.9

44.3

29.3 

26.4 

23.0 

26.8 

32.5 

23.2

52.5 

39.2 

33.3

44.3 

31.0

34.2

45.7 

42.1 

46.6 

38.3 

42.3 

50.2 

41.3 

42.0 

40.6

43.7 

33.4 

38.6 

41.6 

49.1

23.6 

38.9

47.6

Length of 

sample 

(feet)

23.4

60 

65.7 

72 

37 

29.6

30.4

16 

48 

45 

42 

45.5 

55

32 

48.8 

14.5

33.6 

17.6

72

46.5 

23.5 

19 

43 

65 

65 

26 

50 

24

41 

80 

12

44 

43

88

I/ Samples collected by Paul F. Eckstorm and analyzed by D. L. Guernsey at the Massachusetts Institute of Technology.

* Phosphorus and sulfur determined only where figures are given.

t Insoluble in concentrated hydrochloric acid.

J Figures Joined by brackets represent samples taken from adjoining 

parts of the same trench.

The manganese-bearing material in the zone of oxidation, 

including the thin cover of enriched rock, is more promising. 

There are more than 500,000 tons of such material, averaging 

11 percent manganese, at the Dudley farm deposit alone. Mill
152 STRATEGIC MINERALS INVESTIGATIONS,' 1943

tests are now being conducted on carload samples of the ore, 

but no final statement of results is yet available. The Maine 

deposits of partly oxidized ore compare favorably In tonnage 

"and grade with other low-grade manganese deposits In the 

United States, but considerable Improvement in present methods 

of extraction may be necessary before these deposits can be 

utilized.

The Aroostook County deposits contain a tremendous tonnage 

of potential manganese ore below the zone of oxidation. 

Extraction of manganese from these rocks, however, is considerably more difficult than its extraction from the oxidized 

rocks. Whether it will be found practicable to mine the unoxidized manganiferous rock together with the oxidized will 

dejpend entirely on what new methods of recovery can be developed.

The abundance of iron oxide in the deposits suggests that 

they might be 'mined for manganiferous iron ore, as similar 

ores were mined at Woodstock, N. B., during the last century. 

The high silica and phosphorus content of the ore and the 

intimate mineral intergrowths are probably unsurmountable 

obstacles to the production of a smelting ore under present 

market conditions, but iron might form a valuable byproduct of 

manganese extraction. The rocks of the Houlton area contain 

magnetite and coxild easily be so treated as to produce a highIron concentrate.

All of the larger deposits can readily be reached by 

roads, and none is more than 5 miles from a railroad siding.

FUTURE EXPLORATION

If the known deposits prove to be worth mining, additional 

ore deposits may be sought In two ways. First, the extent of 

the known deposits could be determined by trenching ,and drilling. Trenches should be put down to depths of at least 2 feet
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 153

below the top of the bedrock, and a few test shafts would be 

advisable. Second, new deposits might be found along the projections of known deposits and within the stratigraphlc zones 

known to contain manganiferous rocks. Geophysical methods 

could very profitably be used in this work. As the manganiferous rocks of the Houlton area contain magnetite, they can be 

detected with a dip needle. K

DESCRIPTION OP DEPOSITS

Presque Isle area 

. Higgins farm

Eighty feet south of the Bangor & Aroostook Railroad 

tracks and 1.35 miles N. 73° E. of the railroad bridge in 

Mapleton there were, in the summer of 1941, a trench and.a 

small stripped area. The exposures revealed 23 feet of red 

manganiferous hematitic shale, bounded on the east and west by 

red and green argillites that lie, stratigraphically, not far 

above the Aroostook limestone. The bedding is vertical and 

strikes about N. 15° W. A sample across the manganlferous 

zone averaged 17.6 percent manganese, and some hand specimens 

of the rock show many thin bands of manganlferous carbonate. 

In the railroad cut northeast of the trench, a layer of manganif erous rock about 20 feet thick is exposed. Three more out-

« 

crops, all very small, were found between the trench and the

highway 1,700 feet -to the south. The outcrops are not alined

parallel to the strike of the rocks or to one another, a fact

(

which may be due either to 'structural displacement or to 

stratlgraphic discontinuity. .

The Manganese Ore Co. began to explore this deposit by 

drilling and trenching in the fall of 1942, but the de-velop4/ Numbers in parentheses correspond to those designating localities 

in plates 24 and 26.
154 STRATEGIC MINERALS INVESTIGATIONS, 1943

ment work had not progressed far enough at the time of the 

writer's visit to reveal any signifipant new facts.

Dudley farm (2)

The largest individual deposit of manganiferous shale in 

the Presque Isle area is on the Dudley farm, in Castle Hill 

township, 1.5 miles due west of the railroad bridge in Mapleton (pi. 25). The deposit trends nearly north-south in the 

southern part, but bends to about N. 30° E. in the northern 

part; the dip is 60° E. at the south end and steepens northward. The rocks belong to the lower part of the formation 

Immediately overlying the Aroostook limestone.

Trenches dug by the State of Maine in 1941 and by the Manganese Ore Co. in 1942 show that for at 'least 2,200 feet along 

the strike the deposit is nowhere less than 100 feet wide. 

The average width for this distance is about 125 feet. The 

ore body tapers southward, apparently by lateral gradation 

into red shales, but it may continue northward for a considerable distance beyond the northernmost trench shown in plate 

25. The trenching program was not completed at the time of 

the writer's visit, information regarding vertical extent and 

grade has been obtained by diamond drilling. Holes were put 

down at 40° to 45° from the horizontal both eastward and westward from the midpoint of some of the trenches, and another 

hole at about the same angle was drilled from the east end of 

each of these trenches. Three test shafts, also, were sunk 

for the purpose of obtaining large samples down to a depth of 

20 feet for mill tests. The exploration has shown the continuity of the manganif erous zone to 'depths of over 150 feet, 

with a probable average manganese content of 11 percent. 

There appears to be a body more than 2,000,000 tons of manganiferous shale more or less proved; but how much, if any, of
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 155

this material can be rained commercially depends on the results 

of the metallurgical tests that are now being made.

Turner road (3)

On the west side of Turner road, in Castle Hill township, 

3.2 miles N. 60° W. of the railroad bridge in Mapleton, there 

are several scattered outcrops of manganiferous hematltic 

shale that belongs to tne lowest member of the Aroostook limestone. The dip varies from steeply eastward to vertical. The 

manganiferous shales crop out at intervals for half a mile 

along a north-south line, but the average width of the zone is 

probably not more than 20 feet. No trenches were dug or samples taken at this locality.

Castle Hill Grange Hall (4)

In a small pasture a few hundred feet northwest of the 

Castle Hill Grange Hall and about 1.5 miles N. 70° W. of the 

railroad crossing at the village of State Road (Mapleton township), there are outcrops of manganiferous hematitic shale 

that belong to the lower member of the Aroostook limestone. 

The rocks strike northward and dip 80° W, to vertical. A 

trench about 500 feet N. 25° W. of the hall reveals'about 30 

feet of manganiferous rocks, containing on the average 9.2 

percent manganese, which can be traced almost continuously for 

800 feet in a field to the north and seem to maintain a fairly 

constant width. An outcrop still farther north along the 

strike suggests that the zone is cut off by a fault Just north 

of the state road. A second band of manganiferous shales, 

which seems to be about 40 feet wide, lies 400 feet west of 

the first. It was not trenched or sampled, and detailed mapping failed to show whether it is a separate band or the first 

band repeated by faulting. It can be traced by a few scattered outcrops for about 700 feet.
156 STRATEGIC MINERALS INVESTIGATIONS, 1943

Gelot Hill (5)

At the top of Gelot Hill, in New Sweden township, in an 

area extending about 900 feet north-northeast and 100 feet 

wide, the soil is dark and contains abundant float of hematitic shale. Two trenches dug across this area in 1941, after 

the writer had left the region, revealed a manganiferous zone 

with an average width of 105 feet and an average manganese 

content of 8.7 percent. The deposit may well continue farther 

north and south, but no estimate can be made of its extent.

Another trench 800 feet west-southwest of the top of the 

hill, in a similar stained area, revealed a zone 42 feet thick 

with an average manganese content of 12.2 percent. The zone, 

as traced by float, extends slightly east of north for at 

least 400 feet. Considerable shale is exposed between this 

zone and the top of the hill, but exposures are inadequate to 

determine whether there are two zones, or one zone repeated by 

folding or faulting.

Excellent exposures in the road 1,500 to 2,000 feet to the 

west and southwest reveal a few small hemati-tic bands, all 

less than 10 feet in width.

On Gelot Hill, and on Capitol Hill to the southwest, the 

distribution of outcrops suggests that the rocks are much 

faulted and folded, but the exposures are not sufficient for 

working out the structure. Adequate exploration of deposits 

on these hills would probably require trenching at smaller 

intervals than is necessary in other parts of the Presque Isle 

area.

Capitol Hill (6)

A long trench 4,000 feet N. 39° E. of New Sweden crosses a 

Steeply pitching fold in 40 feet of hematitic shale and manganese-stained red slate. The average manganese content for 30
.MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 157

feet of this thickness is 12.9 percent. No other outcrops 

were seen In the immediate vicinity.

Manganiferous hematitic shale Is exposed in road cuts 

1,600 and 2,000 feet east of New Sweden, and in a field northeast of them. The manganiferous zone at these places Is only 

a few feet thick.

At a point 350 feet east of the road and 0.65 mile south 

of New Sweden, a zone of red slate about 100 feet wide contains 5 to 10 feet of hematitic shale. Scattered outcrops oi 

the zone were found for a quarter of a mile in both directions 

along a line trending N. 35° E. No trenches were dug, because 

very little manganiferous rock showed at the surface.

Deposit north of Perham (7)

Outcrops in a field, 400 feet east of a point on the dirt 

road 1.3 miles N. 26° E. of the railroad crossing in Perham, 

reveal a zone of manganiferous chlorlte-caroonate rock 30 to 

35 feet wide. The beds are crumpled, but in general they 

trend N. 25° E. and dip steeply east to vertical. This zone 

Is flanked on each side by a narrower one. One of these, 12 

feet wide, is separated from the middle zone by 15 to 20 feet 

of barren green phyllite; the other, 10 feet wide, Is 60 to 75 

feet from the middle zone. A sample taken across the middle 

zone contained 7.6 percent manganese. The zones can be traced 

by good outcrops for 1,200 feet along the strike, mostly to 

the south of an east-west farm road beside which the sample 

was taken.

At the top and on the south slope of the hill to the west 

a similar zone, about 30 feet wide, can be traced for about 

1,200'feet by small outcrops. No- trenches were dug or samples 

taken here.
158 STRATEGIC MINERALS INVESTIGATIONS, -1943 

Perham village (8)

A small opening 200 feet south of the store in the center 

of Perham partly reveals 40 to 50 feet of manganiferous 

chlorlte-carbonate rock. The bedding strikes N. 15° E. and 

dips 60° NW. A sample taken across 17.5 feet of the richest 

rock contained 11.0 percent manganese, and the average for the 

whole zone is probably between 7 and 9 percent. Scattered 

outcrops suggest that the zone continues up the hill to the 

south for at least 600 feet and probably farther, but its 

width seems to decrease.

Frenchville (9)

Folded manganiferous hematitic shale and red shale crop 

out on a knob that is 0.9 mile N. 50° E. of Thornton School in 

Frenchville and about 8^ miles due west of Mapleton. These 

rocks belong to the lower part of the Aroostook limestone and 

lie but a few hundred feet stratigraphically above the underlying sandstone formation. A long trench roughly parallel to 

the strike reveals about 20 feet of manganiferous rocks, which 

contain 14.2 percent manganese. The only other outcrop of 

manganiferous shale nearby is one about 5 feet wide in the 

middle of the state road 700 feet east-southeast of the knob.

Other' deposits in the Presque Isle area »

The Geological Survey party visited many deposits of manganiferous rocks exposed at other places in the Presque Isle 

area (pi. 24), but none of these deposits is equal to those 

described above in volume of ore exposed and probable manganese content, and they need not be described in detail. Further search for manganiferous rocks should be concentrated on 

the only two atratigraphic units known to contain them. Since 

most of the farmers in the region are aware of the possible 

value of the black-stained manganiferous rocks and are very
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE 159

helpful in imparting any information they may have regarding 

them, it is believed that all the important "bodies and most of 

the minor occurrences in the cultivated areas have been mapped. 

Outcrops of sedimentary rocks are extremely rare and small in 

the adjoining wilderness. There, as one can see but a few 

yards ahead in the dense forest, search for outcrops would 

require many traverses spaced only a few feet apart, ai a cost 

that seems unlikely to be repaid.

Houlton area 

Renderson Hill (10)

The largest deposit of manganiferous rock in the Houlton 

area is on the west side of the top of Henderson Hill, 3,700 

feet S. 60° E. of East Hodgdon and 4.13 miles N. 57° E. of the 

dam in Hodgdon village. The rocks have a fairly constant 

strike of about N. 15° E. and dip 80° E. to vertical. Individual bands of manganiferous rock appear' to be more continuous at this locality than elsewhere in the Houlton area. The 

largest manganiferous zone, which has an average thickness of 

115 feet, is exposed in two trenches 450 feet apart. A few 

small exposures in the woods between the trenches suggest that 

the zone is continuous. The average manganese content is 7.7 

percent. A third trench, 1,200 feet to the south along the 

strike, exposes 130 feet of shale with an average content of 

8.8 percent of manganese. Outcrops are inadequate to determine whether the body of manganiferous rock is continuous 

throughout the intervening 1,200 feet.

In a small patch of woods on the northeast side of the 

hill, near a public road, there is a small body 15 feet wide 

with an average manganese content of 8.3 percent. A few hundred feet still farther north, on the north edge of the patch 

of woods, another trench reveals a zone of about the same
160 STRATEGIC MINERALS INVESTIGATIONS, 1943

width, and according to the owner, Mr. Harry Thwaites, 9 feet 

of this zone contains about 18 percent manganese.

Westford Hill (11 and 12)

Trenches on the three largest outcrops in the Westford 

Hill area are shown in plate 27 (deposit 11, on the south side 

of Westford Hill). The average manganese content of the material exposed here is about 10 percent. This material forms 

bodies averaging 35 feet in width, but they are separated by 

faults and would have to be mined from three separate pits.

A 'small, road-metal quarry, at the base of the southwes't 

corner of Westford Hill (deposit 12), 0.7 mile south of Hodgdon Corners, reveals about 95 feet of manganiferous rocks. 

Outcrops to the north suggest that that zone continues for at 

least 150 feet. The average manganese content is 7.5 percent. 

Scattered outcrops still farther north indicate that the width 

of the zone diminishes northward.

Daggett Hill (14)

Manganiferous rocks are exposed on a small knob 400 feet 

west of Route 1 and 2.32 miles S. 8° E. of Hodgdon Corners. A 

sample from a trench across the bedding, representing about 88 

feet of strata, contained 8.13 percent manganese. A smaller 

sample representing 38 of this 88 feet contained 11.2 percent. 

The rocks are highly folded and may be repeated in the trench. 

As manganiferous rocks cannot be traced away from the knob, 

the deposit is probably s,m§ll. West of the knob, in a road 

cut 70 feet long, 7 feet of> manganiferous rocks are repeated 

several times by folding.

Linneus township (13)

The largest deposits seen in Linneus are on the west and 

southwest sides of the hill 2.2 miles N. 43° E. of the village.
GEOLOGICAL SURVEY BULLETIN 940 PLATE 28

Ordovician graptolite locality

Base map from U.S. Geological Survey 5eology by W.S. White and P.E.CIoud,Jr

GEOLOGIC MAP OF WESTFORD HILL AREA, HODGDON, MAINE 

("A" IN INSET MAP SHOWS LOCATION OF AREA SHOWN IN PLATE 27)

EXPLANATION

Gray and green phyllite

Gray and green phyllite with 

beds of manganirerous hematitic shale and red slate

Outcrops of (a) manganiferous 

hematitic shale and (b) red 

slate

Fault, dashed where inferred 

Boundary of areas mapped
MANGANESE IN EASTERN AROOSTOOK COUNTY, MAINE .161

There are many outcrops of manganiferous rocks on the hill, 

but only one or two bodies of minable size. The largest is 

about 30 feet wide and has an average manganese content of 7.5 

percent.

Other deposits in the Houlton area

In all, about 350 outcrops of manganlferous rocks were 

examined within the areas'indicated in plate 26. At the great 

majority of these outcrops the manganiferous beds exposed were 

only a few feet thick and could be traced for only a short 

distance, and these showings are therefore neglected in calculating tonnages of manganiferous material. Many of them, however, lie near the larger deposits on Hehderson and Westford 

Hills and on the hill in Llnneus. Small ore bodies that lie 

near large deposits probably could be mined. At best, however, the cost of mining very small ore bodies must prove 

relatively high.

Township C t Range 2

A locality on a. hill in Township C, Range 2, outside the 

area examined by the Geological Survey party, was visited by 

Mr. Eckstorm. Small samples collected by him had an average 

manganese content of 9.07 percent.