Lead-Zinc-Silver Deposits 

Related to the White Mountain 

Plutonic Series in 

New Hampshire and Maine

By DENNIS P. COX

CONTRIBUTIONS TO ECONOMIC GEOLOGY

GEOLOGICAL SURVEY BULLETIN 1312-D

A potential target area for mineral 

exploration is indicated by breccia 

veins of argentiferous galena and 

sphalerite, probably introduced during 

igneous activity in the Jurassic

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1970
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

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

Washington, D.C. 20402 - Price 25 cents (paper cover)
CONTENTS

	Page 

Abstract. ________________________________________________________ D 1

Introduction._____________________________________________________ 1

Regional geology and age of mineralization.__________________________ 3

Mineralogy of the deposits.__________--_---__--___-________________ 4

Individual deposits._______________________________________________ 7

Deposits in Madison, N.H. _ _ _..._______.__.______.___..___.____ 7

Mascot and Shelburne deposits, Coos County, N.H. _______________ 11

North Woodstock deposit, Graf ton County, N.H __________________ 14

Mineral Hill deposit, Carroll County, N.H._______________________ 14

Kezar Falls deposit, York County, Maine.___-___--__.______..__. 16

Other deposits.______-___-_-__---------_----_---_---__________ 17

Summary and conclusions._________ __-_---_-_-____-________________ 17

References dited._________________________________________________ 18

ILLUSTRATIONS

Page

FIGURE 1. Map showing lead-zinc-silver deposits of eastern New Hampshire and southwestern Maine and distribution of intrusive 

rocks of the White Mountain Plutonic Series..-.---------- D 2

2. Photomicrograph showing quartz, galena, sphalerite, danalite(?), and other minerals in vein cutting altered mafic rock, 

Silver Lake deposit-__________________--________---__-- 6

3. Photomicrograph showing chlorite and biotite in vermiform

aggregates in coarse vein quartz, Silver Lake deposit--...-- 7

4. Photograph showing fluorite and vermiform aggregates of

chlorite and biotite from fracture in Conway Granite-..-.-- 8

5. Photograph showing mineralized breccia, Silver Lake deposit. __ 9

6. Geologic map of pit rim, Silver Lake mine...____-___-_____- 10

7. Geologic sketch map of Mascot mine.___.--_____-__--_-_-. 12

8. Longitudinal section showing workings in the Shelburne mine. 13

9. Geologic sketch map of North Woodstock mine.__--.------- 15

10. Photomicrograph showing breccia of jasperoid in matrix of

microcrystalline quartz, Kezar Falls deposit._____________ 16

in
>
CONTRIBUTIONS TO ECONOMIC GEOLOGY

LEAD-ZINC-SILVER DEPOSITS RELATED TO THE WHITE 

MOUNTAIN PLUTONIC SERIES IN NEW HAMPSHIRE

AND MAINE

By DENNIS P. Cox

ABSTRACT

Silver-bearing galena and sphalerite occur in mesothermal and epithermal 

deposits in post-Acadian fault-breccia veins in eastern New Hampshire and southwestern Maine. For the most part, the deposits cut Silurian-Devonian schist and 

granite and are in a north-trending belt that coincides with the belt of plutons 

of the White Mountain Plutonic Series of Triassic or Jurassic age. The Conway 

Granite, the youngest formation of the series, is proposed as the source of the 

deposits. The most important deposits are at Silver Lake in Madison, Carroll 

County, N.H., and at the Mascot mine in Gorham, Coos County, N.H.

The Silver Lake deposit contains galena, sphalerite, quartz, chlorite, fluorite, 

sphene, hematite, and danalite( ?). These same minerals occur in a beryllium-iron 

deposit that cuts Conway Granite in Bartlett, Carroll County, N.H. Chlorite, 

fluorite, and danalite(?) also coat small open fractures in the Conway Granite. 

Solutions rising from deeply buried parts of the Conway Granite plutons are 

believed to have caused mineralization of the chilled outer zones and to have 

formed all the breccia veins of the group.

INTRODUCTION

The lead-zinc-silver deposits of eastern New Hampshire and southwestern Maine (fig. 1) have been known since the early 19th century. 

Several of them were described by Jackson (1844) and Hitchcock 

(1878), and many have been included in mineral and economic studies 

of New Hampshire (Larrabee, 1929 ;* Meyers, 1941; Pearre and 

Calkins, 1957). The deposits have not been worked since World War I, 

and even in their most active periods of exploitation, they did not con1 Larrabee, D. M., 1929, Preliminary mineral survey of New Hampshire: Boston, MassNew England Power Assoc., 150 p. (Unpublished report available a<t New Hampshire State 

Plan, and Develop. Comm., Concord, N.H.)

Dl
D2 CONTRIBUTIONS TO ECONOMIC GEOLOGY

EXPLANATION

Batholiths, stocks, and ring dikes 

of White Mountain Plutonic 

Series

X X 

Mine from which some Other mines and 

production is re- prospects 

corded or assumed

1 Simms Stream

2 Clear Stream

3 Mascot

4 Shelburne

5 Iron Mountain

6 North Woodstock

7 Banks, Burk, 

and Hoyt

8 Silver Lake

9 Kezar Falls

10 Mineral Hill

11 Silverdale

50 5 10 15 MILES

FIGURE 1. Lead-zinc-silver deposits of eastern New Hampshire and southwestern 

Maine and their relation to intrusive rocks of the White Mountain Plutonic 

Series.
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE D3

tribute importantly to national mineral production. They are of interest, however, because their distribution outlines an area in which mesothermal and epithermal silver deposits are targets for exploration. 

Moreover, the deposits represent a period of mineralization that can 

be shown to be post-Acadian and probably Mesozoic in age. The 

relation between copper, silver, and barite mineralization and Triassic 

faulting and volcanism has long been known in western Connecticut 

and Massachusetts, but a Mesozoic age for mineral deposits in eastern 

New Hampshire and southwestern Maine has not, until now, been 

reported.

The deposits were studied during an appraisal of silver resources 

of New England, part of the U.S. Geological Survey's Heavy Metals 

program. The writer was assisted in part of the field study by John 

P. D'Agostino and Alien V. Heyl. Mary E. Mrose and Ralph Christian 

provided mineral identifications by X-ray diffraction and X-ray 

fluorescence methods.

Because of the reconnaissance nature of the study, only chip samples 

of veins and random and selected samples of dump materials were collected. Gold was determined by combined fire-assay and atomicabsorption techniques, silver by atomic-absorption spectrophotometry, 

and other metals by semiquantitative spectrographic analysis. Although these analyses serve well to indicate the general level of the 

metal content of ores and minerals, they should not be interpreted as 

accurate assays.

REGIONAL GEOLOGY AND AGE OF MINERALIZATION

The region in which these deposits occur is characterized by schists 

of Devonian and Silurian age, which were, for the most part, metamorphosed to sillimanite grade during the Acadian orogeny. These 

are intruded by syntectonic granite rocks of Devonian age, known as 

the New Hampshire Plutonic Series.

Lead-zinc-silver deposits are in a north-trending belt which crosses 

the strike of metamorphic and syntectonic granite rocks and which 

coincides roughly with the belt of posttectonic plutons of the White 

Mountain Plutonic Series (fig. 1). This series is of Triassic or Jurassic 

age and is characterized by granite, syenite, monzonite, diorite, and 

gabbro (Billings, 1956, p. 146). The Conway Granite, the youngest and 

most widespread unit of this series, has been dated at about 185 million 

years (Toulmin, 1961).

The deposits have many mesothermal and epithermal features and 

were formed in open fractures, as indicated by abundant vugs and by 

quartz crystals showing comb structure. The veins were formed from
D4 CONTRIBUTIONS TO ECONOMIC GEOLOGY

solutions that were out of chemical equilibrium with the wallrocks, 

as indicated by extensive hydrothermal alteration halos around the 

veins. The deposits are younger than aphanitic dike rocks, which were 

apparently intruded at relatively shallow depth. In addition, most 

mineralized fractures are characterized by extensive breccia, which 

suggests tensional, rather than shear, stress during their formation. All 

these features show that these deposits were formed most certainly 

after the Acadian orogeny and probably after a considerable period of 

uplift and erosion, at a level in the crust where open space could exist 

and where igneous rocks could crystallize as aphanites. Such an environment for mineral deposition probably existed during and immediately after the intrusion and crystallization of plutons and dikes of the 

White Mountain Series.

The deposits, for the most part, are in fractures cutting schist and 

syntectonic granitic rocks, but one deposit, at Iron Mountain, N.H. 

(fig. 1, loc. 5), is within the Conway Granite of the White Mountain 

Plutonic Series. The source of mineralizing solutions is probably the 

Conway Granite itself, as no younger thermal events capable of forming such deposits have been recognized in this part of New England. 

Doming of the crust in response to the intrusion of magma may have 

opened channelways in the country rock as well as in the early crystallized roof zones of the Conway Granite at Iron Mountain.

MINERALOGY OF THE DEPOSITS

Galena is present in all the deposits and is the main ore mineral in 

all but the Iron Mountain deposit. Silver content of the galena ranges 

from 0.02 to 0.5 percent, the highest value being found at the Shelburne mine, the lowest, at the North Woodstock and Silverdale mines 

(fig. 1, Iocs. 4, 6,11). Galena from the other deposits contains about 0.1 

percent silver. Bismuth content ranges from 0.1 to 1.5 percent in 

galena from Iron Mountain, Silver Lake, Kezar Falls, and Mineral 

Hill (fig. 1, Iocs. 5, 8, 9, 10); the other deposits contain little or no 

bismuth. Galena from Mascot (fig. 1, loc. 3) and Shelburne contains 

0.01 to 0.03 percent tin.

Sphalerite is abundant in all the deposits except Iron Mountain and 

North Woodstock, where it is rare. At the Mascot and Shelburne 

deposits, sphalerite is dark brown to black, but in the other deposits the 

mineral is characteristically honey brown. Sphalerite from the Silver 

Lake, Kezar Falls, Mineral Hill, and Silverdale deposits contains 1.5 

to 2 percent cadmium and 1 to 1.5 percent iron.

Chalcopyrite is a minor constituent of the ores at Mascot, Shelburne, 

and Mineral Hill.
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE D5

Quartz, carbonate minerals, and pyrite are the predominant gangue 

minerals in all deposits of this group. Quartz is commonly milky and 

coarsely crystalline. At Shelburne, coarse comb-structured quartz 

masses are crossed by concentric spherical color bands with a pattern 

suggesting botryoidal texture of originally amorphous silica. At Kezar 

Falls, comb-structured quartz grades into microcrystalline quartz.

Carbonate minerals are minor constituents of veins in all deposits 

except at Mascot and Shelburne, where coarsely crystalline manganosiderite makes up major parts of the vein. Unidentified carbonate minerals are important 'alteration products in wallrocks at Mascot, Iron 

Mountain, North Woodstock, and Silver Lake.

Small amounts of pyrite are everywhere present, and arsenopyrite 

was noted in the Shelburne vein.

Kaolin, in finely crystalline masses, forms coatings on the walls of 

vugs in the Kezar Falls vein. This mineral, plus the above-mentioned 

microcrystalline quartz, indicates an epithermal classification for the 

Kezar Falls deposit.

A group of distinctive minerals in the Silver Lake deposit are important in determining the age and source of this deposit and, by extension, 

of the other deposits of this group. These minerals, hematite, sphene, 

fluorite, and a helvite-group mineral tentatively identified as danalite, 

occur in the Silver Lake deposit as well as in the Iron Mountain 

deposit, which cuts Conway Granite.

The two deposits are otherwise quite different in character. The Iron 

Mountain deposit comprises several lenses of magnetite, hematite, and 

beryllium minerals formed by replacement of Conway Granite along 

northeast-trending joints (Barton and Goldsmith, 1968, p. 58, 59). 

Veinlets and lenses of vuggy quartz containing galena and sphalerite 

are closely associated with the beryllium-iron ore. The Silver Lake 

deposit, more typical of the group as a whole, is a breccia vein composed of vuggy quartz and silicified granitic rock containing galena 

and sphalerite.

Hematite occurs as bladelike disseminations and rosettes in altered 

Conway-Granite at Iron Mountain and in chloritized mafic dike rock 

at Silver Lake. At Iron Mountain, danalite occurs with phenacite in 

altered granite and in the vuggy quartz veinlets. At Silver Lake, danalite ( ?) is rare and is restricted to quartz veinlets in altered mafic dike 

rock (fig. 2). Very small euhedral grains of sphene are disseminated in 

quartz veins at Silver Lake and in altered granite at Iron Mountain. 

Fluorite, as coarse purple crystals, is rare in both deposits.

665-572 O 7C
D6 CONTRIBUTIONS TO ECONOMIC GEOLOGY

Chlorite interleaved with biotite occurs in quartz veinlets at Silver 

Lake and as crusts on open fractures in Conway Granite in the Madison 

quarry, 6.5 miles north of the Silver Lake deposit. In both occurrences 

the chlorite-biotite mixture has a peculiar vermiform habit (figs. 3 and 

4). The fractures at Madison quarry also contain purple fluorite and 

rare crystals of danalite (?).

The similarities in mineral assemblages in the Silver Lake deposit 

and in the Iron Mountain deposit and the late fracture fillings in the 

Conway Granite strongly suggest a common source. All the deposits 

of this group are probably related to the last stages of White Mountain 

plutonic activity and are thus Triassic or Jurassic in age.

FIGURE 2. Vein containing quartz (Q), galena (G), sphalerite (S), danalite'.' 

(D), hematite (H), chlorite (C), and finely disseminated sphene and chlorite. 

Vein cuts altered mafic rock (M). Silver Lake deposit. Plane-polarized light.
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE D7

FIGURE 3. Chlorite and biotite in vermiform aggregates in coarse vein quartz. 

Opaque mineral is hematite. Silver Lake deposit. Partly crossed polarizers.

INDIVIDUAL DEPOSITS

In the following descriptions, the Iron Mountain deposit, Bartlett, 

N.H., is omitted. A detailed account of this deposit has been given by 

Barton and Goldsmith (1968, p. 51-67).

DEPOSITS IN MADISON, N.H.

The largest and earliest known deposit of this group is at the Silver 

Lake mine in Madison Township, N.H., near the south end of Silver 

Lake (43°51'15" N., Tl°9'15" W.). Three small prospect shafts the 

Bank, Burke, and Hoyt mines are near the north end of Silver Lake 

(43°53'30" N., 71°9'30" W.), and another prospect shaft is about 2 

miles to the east (43°52'40" N., 7l°7'25" W.).
D8 CONTRIBUTIONS TO ECONOMIC GEOLOGY

FIGURE 4. Fluorite and vermiform aggregates of chlorite and biotite. Fracture 

coating in Conway Granite, Madison quarry.

The Silver Lake mine, also known as the Madison, Eaton, or Ossipee 

mine, was opened in 1826 and worked for a short time (Merrill, 1889, 

p. 806). Production and periods of activity are not precisely known for 

the early history of this mine, but Jackson in 1841 (1844, p. 83) reported a 40-foot shaft on the property, and Hitchcock in 1878 (p. 63) 

reported a daily production of one or two barrels of concentrate containing 70 percent lead.

A long period of idleness, interrupted briefly in 1906-7, ended in 

1913 when a gravity mill was built by the New Hampshire Mining 

and Milling Co. During the period 1915 to 1918, an open pit, 170 feet 

by 40 feet by 60 feet deep, was developed. In 1918, the property was 

leased to the New Jersey Zinc Co., who did exploration work at a depth 

of 200 feet. Operations were suspended 6 months later. The mill burned 

in 1943.

The geology of the Ossipee Lake quadrangle, in which the Madison 

deposits are located, was described by Wilson (1965). The area is 

underlain by mica schist of Devonian age containing abundant pegmatite stringers and small granitic bodies. Batholiths and stocks of
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE D9

the New Hampshire Plutonic Series of Devonian age and Conway 

Granite of Triassic or Jurassic age are a few miles north and south of 

the deposits.

Eocks in the immediate vicinity of the Silver Lake mine are very 

poorly exposed. Dump materials and outcrops around the rim of the 

water-filled open pit indicate that galena and sphalerite are disseminated in silicified and brecciated quartz monzonite and in chloritized 

and brecciated mafic rock, the origin of which is not known (fig. 5).

The structure of the deposit is known only from mapping of the pit 

rim (fig. 6). A dominant set of fractures with steep but variable dip 

trends N. 20° E., and a less well developed set strikes N. 60° E. These 

are cut by widely spaced fractures trending N. 85° E., one of which 

contains an altered mafic dike about 10 feet thick. No continuation of 

the silicification zone or ore mineralization outward from the pit was 

detected, but 300 feet south of the pit, many small exposures of altered 

granitic rock follow a N. 35° E. trend. This trend of outcrops does 

not intersect the pit area.

Production of about 20,000 tons of ore containing 10 percent combined lead and zinc has been reported (McHenry Mosier, U.S. Bur. 

Mines, written commun., 1949). Comparison of ore and metal produc2cm

FIQUEE 5. Mineralized breccia from Silver Lake deposit, showing fragments of 

silicified granite (gr) and chloritized mafic rock (M) in matrix of quartz, galena, 

and sphalerite.
D10 CONTRIBUTIONS TO ECONOMIC GEOLOGY

#

EXPLANATION

Mafic dike, showing dip 

Dashed where inferred

Fractures in silicified and brecciated 

granitic rock, showing dip

Dashed where inferred

Major fracture or fault, showing dip 

Dashed where inferred

20 0 

I i I

FIGURE 6. Geologic map of pit rim, Silver Lake mine, Madison, N.H.

tion for 1917 (Hill, 1921, p. 58) indicates that 3 percent would be a 

more reliable figure. The New Jersey Zinc Co. reported 15 feet of ore 

containing 3.7 percent combined lead and zinc at the 200-foot level 

(McHenry Mosier, written commun., 1949).

One or two ounces of silver and a trace of gold were found in selected 

dump samples, which also contain 2 percent lead, 5 percent zinc, and 

minor amounts of beryllium and lanthanum. Ore in mafic rock contains as much as 0.03 percent Be, and one silicified quartz monzonite 

ore sample contains 0.3 percent La. Beryllium in the ore is in danalite, 

and lanthanum and other rare earths probably are carried by sphene.

Three trays of mineral concentrate were found in the burned ruins
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE Dll

of the mill. These concentrates contain 5-20 ounces of silver per ton, 

0.07-0.3 percent bismuth, and 0.15-2 percent cadmium. The most 

abundant rare earths in these concentrates are cerium, 0.02-0.07 percent, and neodymium, 0.01-0.05 percent. Beryllium content is very 

small.

Samples of mill tailings contain 0.15-0.5 percent lead, 1-3 percent 

zinc, and 0.06-0.3 ounces of silver per ton.

MASCOT AND SHELBURNE DEPOSITS, COOS COUNTY, N.H.

Lead-, zinc-, and silver-bearing minerals occur in veins cutting schist 

and granitic rocks of Devonian age on the slopes of Mount Hayes, in 

Gorham and Shelburne Townships, Coos County, N.H. Two mines 

have been developed on these veins: the Mascot (44°24'00"N., 

71°10'40"W.), 1 mile north of Gorham, and the Shelburne (44°25' 

10"N., 71°7'50"W.), on the west fork of Leadmine Brook.

The Mascot breccia vein is exposed on a high ledge for a vertical 

distance of more than 200 feet. During the period 1881 to 1885, aditdrifts were driven on the vein at three levels connected by stopes (fig, 

7), and about 50,000 tons of vein material was mined. A mill was constructed which produced ll/2~W2 tons of concentrate per day; at least 

30 tons of concentrate containing 70-82 percent lead and 28 ounces of 

silver per ton was reported shipped to New Jersey (Maine Mining 

Jour., Jan. 23, 1885). In 1906, during a second period of activity, 70 

tons of lead and 174 ounces of silver were produced (McCaskey, 1908, 

p. 561).

The Mascot breccia vein, which strikes N. 35°-45°-E. and dips 

70° NW., is 10 to 20 feet wide and comprises angular fragments of 

altered granitic rocks with interstitial quartz and manganosiderite. In 

the upper drift-adit, a vertical aphanitic dike has been shifted 24 feet 

on three distinct faults (fig. 7).

Granitic rocks in and near the vein are sericitized; feldspar is 

altered to fine-grained sericite, and biotite to colorless mica clouded 

with rutile needles. Pyrite is disseminated throughout. Dike rocks are 

almost completely altered to sericite, chloritfy and carbonate minerals, 

but show relict phenocrysts of plagioclase and mafic minerals and 

relict plagioclase laths in the groundmass.

Ore minerals are commonly restricted to thin seams within the vein. 

These have been variously reported as galena in masses 4 inches to 10 

inches thick or as three mineral bands together totaling 22 inches in 

thickness (Maine Mining Jour., Dec. 1, 1882; Mar. 2, 1883). Galena 

occurs as coarse grains having strongly deformed cleavage surfaces or 

as fine "steel galena." Deformation of galena indicates postdepositional 

movement along the vein.
D12 CONTRIBUTIONS TO ECONOMIC GEOLOGY

EXPLANATION '

Inaccessible stope x 

Sample 1\

Granitic rock

Quartz-manganosiderite veins

+ + +

Aphanitic dike

J Stoped 

65 feet 

to surface

1 70

Fault, showing dip 

Dashed where approximafe/y located

Middle adit

' / Stope -J 

-'"oo / connected _

Upper adit 

^ (65 feet above middle adit)

20 FEET

FIGUBB 7. Geologic sketch map, Mascot mine, Gorham, N.H. Note displacement 

of dike by faults in upper adit.

Two chip samples (fig. 7) were cut during the present study across 

3 feet of vein in a short drift north of the main upper drift-adit and 

across 2 feet of coarse manganosiderite in the middle drift-adit. They 

contain, respectively:

Ore mineral Sample 1 Sample 2

Zinc _____; __ .percent 10 3

Copper ____________________.._do__ 5 0.15

Lead _ ________ ____ _do__ 0.3 0.05

Silver __________ounces per ton__ 3 0.09

Gold __________________________do__ 0.009 0.002

The Shelburne vein strikes N. 75° E. along the bed of the lower 

part of the west fork of Lead Mine Brook. Three shafts were sunk 

on the exposed 300 feet of vein in the streambed, and a 30-foot adit 

was driven westward on the vein where the streambed diverges 

sharply to the north (fig. 8). One shaft has a brick collar 10 feet high, 

which apparently served to protect the shaft from flooding. Mining
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE D13

began during the late 1830's (Jackson, 1844, p. 102) and continued 

intermittently during the 1850's. Probably only small amounts of ore 

were shipped. A final attempt to work the mine in 1880 was 

unsuccessful.

The Shelburne vein is 10 to 15 feet wide and similar in its structure 

and texture to the Mascot vein. Breccia fragments of schistose and 

granitic rocks are enclosed in comb-structured quartz and carbonates. 

Sulfides occur in thin seams and patches. Figure 8 shows the outline 

of a stope developed on a rich part of the vein in which the combined 

width of sulfide seams is as much as 20 inches (Hodge, 1853, p. 30). 

Efforts to find other high-grade shoots were apparently unsuccessful. 

Chip samples were taken during the present study across high-grade 

parts of the vein. They contain the following values:

Vein width_________________feetLead __________________.percent 

Zinc _-__________________-do__ 

Tin _____________________do__ 0.003 

Silver_______________ounces per ton__

Sample

1

1

10

3

0.003

6

&

1

7

1

0.003

9

3

3

0.7

0.7

0.001

0.9

Gold .do. 0.002 0.002

West East

FIGURE 8. Longitudinal section showing workings in the Shelburne mine, Shelburne, N.H. Modified from Hodge (1853, p. 30).
D14 CONTRIBUTIONS TO ECONOMIC GEOLOGY

NORTH WOODSTOCK DEPOSIT, GRAFTON COUNTY, N.H.

The North Woodstock mine is on the south side of a steep ravine 

formed by Beaver Brook about 2,000 feet west of its confluence with 

the Pemigewasset Eiver (43°59'30" N., 7l°41'20" W.), in Grafton 

County, N.H. A 230-foot adit follows a fault, and a pocket of ore 

has been stoped to the surface. A mill foundation near the portal suggests that ore production was at least contemplated, though no record 

of production could be found.

Figure 9 is a sketch of the adit showing a contact between granitic 

rock and schist cut at a small angle by a fault. No true quartz vein 

has formed in this deposit as in others of this group. Galena and minor 

sphalerite and pyrite are disseminated in quartz-ankerite-sericite rock 

derived from alteration of the country rock. The quartz-ankeritesericite zone is limited to a few inches along the fault where it cuts 

schist, but it extends nearly 10 feet out from the fault in the granitic 

rock. Galena, sphalerite, and pyrite are disseminated only in the altered granitic rock.

A chip sample across 7 feet of altered granitic rock contained 0.7 

percent lead, and 0.13 ounces silver per ton.

MINERAL HILL DEPOSIT, CARROLL COUNTY, N.H.

The Mineral Hill deposit, in the north corner of Wakefield Township, Carroll County, N.H. (43°40'30" N., 7l°00'30" W.), is on several 

veins that strike N. 60°-65° E. and dip steeply north. A shaft was 

sunk on a vein to a depth of 118 feet (Maine Mining Jour., Oct. 22, 

1880) and a short adit-drift was opened on another. No ore production 

was reported.

The deposit comprises quartz veins and podlike masses of silicified 

breccia following a fault system. A fault exposed in the adit strikes 

N. 60° E. and dips 60° NW. Another fault exposed in the shaft 

strikes N. 75° E. and dips 70° NW. There is no apparent continuity 

of faults or veins, but sporadic outcrops of silicified breccia form two 

parallel northeast-trending bands 1,000 feet long and 300 feet apart.

The country rock is mainly quartz monzonite of Devonian age intruded by large irregular bodies of fine aplitic quartz monzonite and 

by thin dikes of mafic aphanitic rock. An irregular zone of hydrothermal alteration as much as 200 feet wide follows the vein. In this 

zone, plagioclase is partly sericitized, biotite is bleached or chloritized, 

and the rocks are crossed by closely spaced veinlets of quartz, some 

of which are iron stained.

Ore specimens collected from the main shaft dump contain patches 

of galena, brown sphalerite, chalcopyrite, and pyrite in coarse combstructured quartz. Two dump samples were collected; one sample
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE D15 

\

\

Fault in ~7 

streambed '

\

Stope in altered granitic . 

rock. Caved to surface

EXPLANATION

quartz-sencite-carbonate alteration

Granitic rock

Contact 

Dashed where approximately located

Fault, showing dip

20 FEET

Schist along fault, 

slightly mineralized

FIGURE 9. Geologic sketch map, North Woodstock mine, North Woodstock, N.H.

was made by combining grab samples collected at intersections of a 

5-foot grid pattern laid out on the dump surface; another sample 

comprised material from two 3-foot vertical cuts in the edge of the 

dump. Vertical and surface samples both contained 0.3 ounce of 

silver per ton, a trace of gold, 0.4 percent lead, 1.3 percent zinc, and
CONTRIBUTIONS TO ECONOMIC GEOLOGY

0.3 percent copper. If it is assumed that no ore was shipped from the 

mine, the values may be taken as an approximation of the metal 

content of the vein and its wallrocks where cut by the shaft.

KEZAB PALLS DEPOSIT, YOKK COUNTY, MAINE

A small silver-lead vein is one-half mile south of Kezar Falls in 

Parsonfield, York County, Maine (43° 4Y'55" N., 70°53'25" W.). No 

record of production from this deposit was found. Mine workings 

consist of three shallow pits that may have been shafts. The vein 

strikes N. 40° E., dips 50°-55° NW. and can be traced for about 650 

feet. Segments of the vein 5-100 feet long have divergent trends 

ranging from N. 25° E. to N. 55° E. The vein is cut by unaltered 

dolerite dikes. Ore minerals were not noted in the vein outcrop, but 

boulders dug from the dump provided a rough idea of the nature 

of the ore.

Galena and sphalerite occur as coarse crystals in breccia composed 

of fragments of dark-gray jasperoid so clouded with fine inclusions 

as to be opaque in thin section (fig. 10). The breccia is filled by 

microcrystalline quartz, fine comb-structured quartz, and kaolinite.

V-Xs" S^p^ftatt.- W> *< ?> ~?&H- S<&X*

 ' l''J'-'fl~r'Jr,ClL '^ ">rf y / * ? «*4> T^*'' *V *J'

SKilMM^?^ r ^'^MiS

FIGUKE. 10. Breccia containing fragments of jasperoid. Matrix is microcrystalline 

quartz grading into fine comb-structured quartz. Kezar Falls deposit. Partly 

crossed polarizers.
LEAD-ZINC-SILVER DEPOSITS, NEW HAMPSHIRE AND MAINE D17

OTHER DEPOSITS

Three shallow shafts constituting the Silverdale mine have been 

sunk on a quartz vein in Pittsfield, Merrimack County, N.H. (43° 16' 

45" N., 71°20'30" W.) The vein, which strikes N. 28° E. and can be 

traced for 1,000 feet, is as much as 15 feet wide and is composed of 

many parallel and intersecting veinlets of comb-structured quartz. 

It contains coarse patches of galena and brown sphalerite.

Galena and sphalerite in comb-structured quartz veins Avere noted 

by Norman Hatch (written commun., 1967) in two localities in northern Coos County, N.H. These are on Simms Stream (44°50'50" N., 

71°29'30" W.) and on West Branch of Clear Stream (44°49'20" N., 

71°17W/ W.).

Other deposits may have been overlooked during this study. However, those described seem to be representative and, in general, are 

believed to delineate the area in which this type of deposit occurs.

SUMMARY AND CONCLUSIONS

Eleven silver-bearing galena-sphalerite deposits lie in a northeasttrending belt roughly coincident with the belt of plutons of the White 

Mountain Plutonic Series of Triassic or Jurassic age. The mineralogy 

and spatial relations suggest that the deposits may be related to intrusion and crystallization of these plutons.

Most of the deposits are quartz veins or quartz-filled breccia veins, 

but some, such as the Mascot and Shelburne deposits, are veins mainly 

filled with carbonate minerals. The North Woodstock deposit is not a 

true quartz vein but is a wide sericite-carbonate alteration envelope 

containing disseminated sulfides. Probably most of the outcrops of 

quartz veins and silicified rocks were discovered in this part of New 

England during clearing of land for agriculture 100 years ago. Many 

of these have been explored to considerable depth, some with encouraging results.

Other deposits similar to the one at North Woodstock in which 

sericite and carbonate minerals predominate are less resistant to weathering and glacial erosion. These deposits may have been deeply scoured 

by glaciers and later covered by drift. Thus, linear valleys or chains 

of lakes and swamps that might be controlled by post-Acadian fractures become likely ground for geochemical and geophysical 

prospecting.
D18 CONTRIBUTIONS TO ECONOMIC GEOLOGY 

REFERENCES CITED

Barton, W. R., and Goldsmith, C. E., 1968, New England beryllium investigations: 

U.S. Bur. Mines Rept. Inv. 7070,177 p.

Billings, M. P., 1956, Bedrock geology, pt. 2 of Geology of New Hampshire: Concord, N.H., New Hampshire State Plan, and Devel. Comm., 203 p.

Hill, J. M., 1921, Gold, silver, copper, lead, and zinc in the Eastern States, in U.S. 

Geol. Survey, Mineral resources of the United States, 1917: Washington, 

U.S. Govt. Printing Office., p. 55-62.

Hitchcock, C. H., 1878, Economic geology, pt. 5 [in v. 3] in Hitchcock, C. H., Huntington, J. H., Upham, Warren, Hawes, G. W., 1878, Geology of New Hampshire: Concord, N.H., Edward A. Jenks, State Printer, 103 p.

Hodge, J. T., 1853, Report on the mining properties of the Shelburne Lead Mining 

Co., at Shelburne, New Hampshire: Mining Mag., v. 1, p. 27-34.

Jackson, C. T., 1844, Final report on the geology and mineralogy of the State 

of New Hampshire: Concord, N.H., 376 p.

McCaskey, H. D., 1908, Gold, silver, copper, lead, and zinc in the Eastern States 

(mine production), in U.S. Geol. Survey, Mineral resources of the United 

States, 1907; Washington, U.S. Govt. Printing Office, p. 551-570.

Maine Mining Journal, 1880-86, [various numbers]: Portland, Maine (weekly).

Merrill, G. D., 1889, History of Carroll County : Boston, W. A. Ferguson Co., 987 p.

Meyers, T. R., 1941, New Hampshire minerals and mines, a report to the New 

Hampshire State Planning and Development Commission: Concord, N.H., 

New Hampshire State Plan, and Develop. Comm., 49 p.

Pearre, N. C., and Calkins, J. A., 1957, Mineral deposits and occurrences in New 

Hampshire, exclusive of clay, sand and gravel, and peat: U.S. Geol. Survey 

Mineral Inv. Resource Map MR-6, scale 1:500,000, with text.

Toulmin, Priestley, III, 1961, Geologic significance of lead-alpha and isotopic age 

determinations of "alkalic" rocks of New England: Geol. Soc. America Bull., 

v. 72, no. 5, p. 775-780.

Wilson, J. R., 1965, Bedrock geology of the Ossipee Lake area, New Hampshire: 

Cambridge, Mass., Harvard Univ. unpub. Ph. D. thesis.

U.S. GOVERNMENT PRINTING OFFICE: 1970 O 365-572