Evans and Moyle

U.S. Industrial Garnet

U.S. Geological Survey Bulletin 2209

L

Printed on recycled paper
U.S. Industrial Garnet

By James G. Evans and Phillip R. Moyle

U.S. Department of the Interior

U.S. Geological Survey 

Contributions to Industrial-Minerals Research

James D. Bliss, Phillip R. Moyle, and Keith R. Long, Editors

Bulletin 2209–L

Chapter L of
U.S. Department of the Interior

P. Lynn Scarlett, Acting Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

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Produced in the Western Region, Menlo Park, California

Manuscript approved for publication, March 29, 2006

Text edited by George A. Havach

Layout and design by Stephen L. Scott
Contents

Abstract--------------------------------------------------------------------------------------------------------1

Introduction----------------------------------------------------------------------------------------------------1

Status of U.S. Industrial Garnet-----------------------------------------------------------------------1

Composition of Garnet----------------------------------------------------------------------------------1

Uses of Garnet-------------------------------------------------------------------------------------------2

Industrial Specifications-------------------------------------------------------------------------------3

Evaluation of Garnet Deposits-------------------------------------------------------------------------4

Markets for Garnet--------------------------------------------------------------------------------------5

International Garnet Reserves------------------------------------------------------------------------6

Risks of Production Abroad----------------------------------------------------------------------------6

Competition from Other Natural and Manmade Abrasives----------------------------------------7

Advantages of Garnet----------------------------------------------------------------------------------7

U.S. Garnet Deposits------------------------------------------------------------------------------------------8

Overview-------------------------------------------------------------------------------------------------8

New York-------------------------------------------------------------------------------------------------9

Geologic Setting-----------------------------------------------------------------------------------9

Barton Mines Co., LLC----------------------------------------------------------------------------9

NYCO Minerals, Inc.---------------------------------------------------------------------------- 11

Other Garnet Mines and Deposits------------------------------------------------------------ 12

Northern Appalachian Mountains and New England-------------------------------------------- 13

Geologic Setting--------------------------------------------------------------------------------- 13

Maine ------------------------------------------------------------------------------------------- 13

New Hampshire--------------------------------------------------------------------------------- 17

Vermont------------------------------------------------------------------------------------------ 17

Connecticut-------------------------------------------------------------------------------------- 18

Central and Southern Appalachian Mountains---------------------------------------------------- 18

Geologic Setting--------------------------------------------------------------------------------- 18

Pennsylvania------------------------------------------------------------------------------------ 19

Virginia------------------------------------------------------------------------------------------- 21

North Carolina----------------------------------------------------------------------------------- 21

South Carolina----------------------------------------------------------------------------------- 22

Georgia------------------------------------------------------------------------------------------- 23

Florida ------------------------------------------------------------------------------------------- 24

Western United States------------------------------------------------------------------------------- 25

Idaho--------------------------------------------------------------------------------------------- 26

Placer Garnet Deposits of Northern Idaho--------------------------------------------- 26

Emerald Creek Area---------------------------------------------------------------- 26

Garnet Source----------------------------------------------------------------------- 28

Description of Garnet--------------------------------------------------------------- 30

Garnet in Black Sand Deposits of Central Idaho-------------------------------------- 30

Montana------------------------------------------------------------------------------------------ 32

Overview----------------------------------------------------------------------------------- 32

Ruby Garnet Mine------------------------------------------------------------------------- 33

III
Sweetwater Garnet Mine---------------------------------------------------------------- 35

Evaluation of the Ruby Garnet and Sweetwater Garnet Mines--------------------- 37

Section 36 Deposit------------------------------------------------------------------------ 37

Other Garnet Occurrences--------------------------------------------------------------- 38

Garnet Sources in the Southern Tobacco Root Mountains-------------------------- 38

Alaska-------------------------------------------------------------------------------------------- 39

California----------------------------------------------------------------------------------------- 41

Nevada------------------------------------------------------------------------------------------- 42

New Mexico------------------------------------------------------------------------------------- 42

Oregon------------------------------------------------------------------------------------------- 44

Conclusions-------------------------------------------------------------------------------------------------- 47

Acknowledgments------------------------------------------------------------------------------------------ 47

References Cited-------------------------------------------------------------------------------------------- 47

Figures

- --- --1. Plot of U.S. industrial garnet production for the years 1894–2002---------------------------2

- --- --2. Pie chart showing the principal domestic uses of garnet------------------------------------3

- --- --3. Plot of U.S. garnet value and unit value for the years 1900–2000----------------------------5

- --- --4. Pie chart showing the principal uses of garnet worldwide---------------------------------- 5

- --- --5. Pie chart showing U.S. abrasive-mineral demand for the year 2001------------------------8

- --- --6. Sketch map of the Appalachian Mountains and New England, showing

- --- --- - -areas of basement rocks of the Proterozoic (Laurentian) continental margin

- --- --- - -and adjacent suspect terranes------------------------------------------------------------------10

- --- --7. County map of New York, showing the locations of counties with deposits of

garnet and associated sand and gravel and wollastonite----------------------------------- 11

8–10. Photographs of:

8. Garnet porphyroblast in the Gore Mountain deposit, N.Y., showing typical

cleavage---------------------------------------------------------------------------------------12

9. Garnet ore in the Gore Mountain deposit, N.Y.--------------------------------------------12

10. Garnet ore in the Ruby Mountain deposit, N.Y.--------------------------------------------12

11.- -Isograd map of Taconic metamorphism in New England------------------------------------ 14

12. Isograd map of Acadian metamorphism in New England------------------------------------15

13. County map of Maine, showing the locations of counties with garnet deposits or

- --- --- - -occurrences---------------------------------------------------------------------------------------16

14. Sketch map of northern New England, showing the locations of regional

- --- --- - -structures------------------------------------------------------------------------------------------ 16

15–17.- -County maps of:

15. New Hampshire, showing the location of Merrimac County, which has garnet

deposits---------------------------------------------------------------------------------------- 17

16. Vermont, showing the location of Windsor County, which has garnet

deposits----------------------------------------------------------------------------------------18

17. Connecticut, showing the locations of counties with garnet deposits or

occurrences-----------------------------------------------------------------------------------18

18. Isograd map of Taconic metamorphism in the central and southern Appalachian 

- --- --- - -Mountains----------------------------------------------------------------------------------------- 19 

- --- 19. Isograd map of Acadian metamorphism in the central and southern

- --- --- - -Appalachian Mountains--------------------------------------------------------------------------20 

- --- 20. Sketch map of the Southeastern United States, showing the locations of

- --- --- - -the Raleigh and Kiokee metamorphic belts and their regional setting--------------------- 20

21–27. Maps of:

- --- --- - -21. Pennsylvania, showing the locations of counties with garnet deposits or

occurrences--------------------------------------------------------------------------------20

- --- --- - -22. Virginia, showing the locations of garnet deposits or occurrences-------------------- 21

IV
- - 23. North Carolina, showing the locations of counties with garnet deposits or

occurrences-------------------------------------------------------------------------------- 22

- - 24. South Carolina, showing the locations of counties with garnet occurrences----- 23

- - 25. Georgia, showing the locations of counties and isograds of Taconic

metamorphism north of the Fall Line---------------------------------------------------- 24

- - 26. Florida, showing the locations of counties with occurrences of garnet

or other heavy minerals------------------------------------------------------------------- 25

- - 27. Idaho, showing the locations of counties with garnet deposits--------------------- 26

28. Photograph of recent cut through loess and garnetiferous gravel in the

- - Emerald Creek area, Idaho--------------------------------------------------------------------- 26

29. Photograph of recent cut through barren surface gravel to garnet placer

- - with upper oxidized zone along Carpenter Creek, Idaho----------------------------------- 26

30. Geologic map of the Emerald Creek area, Idaho-------------------------------------------- 27

31. Photograph of star garnet---------------------------------------------------------------------- 28

32. Photograph of metapelite with well-preserved bedding----------------------------------- 29

33. Slope map of part of the East Fork of Emerald Creek, Idaho------------------------------- 29

34. Photomicrograph of inclusions in garnet from the Emerald Creek area,

- - Idaho---------------------------------------------------------------------------------------------- 30

35. Photographs of metamorphic minerals in rocks from the Emerald Creek

- - area, Idaho--------------------------------------------------------------------------------------- 31

36. County map of Montana, showing the locations of counties with garnet

- - occurrences------------------------------------------------------------------------------------- 33

37. Map of part of the Butte, Mont., area--------------------------------------------------------- 33

38. Geologic map of Alder, Mont., area, showing the locations of garnet-rich rocks and

garnet placers ---------------------------------------------------------------------------------- 34

39–41. Photographs of:

- - 39. Biotite schist containing garnet-rich nodules and lenses in the Alder

Gulch area, Mont.--------------------------------------------------------------------------- 35

- - 40. Migmatite in the Alder Gulch area, Mont.------------------------------------------------ 35

- - 41. Red Wash deposit, Mont.------------------------------------------------------------------ 36

42. Map of the Sweetwater Creek area, Mont., showing the locations of the

- - Sweetwater Garnet Mine and Section 36 garnet deposit---------------------------------- 37

43–45. Photographs of:

- - 43. Pit wall at the Sweetwater Garnet Mine, Mont.----------------------------------------- 37

- - 44. Garnet-rich saprolite south of the Sweetwater Garnet Mine, Mont.----------------- 37

- - 45. Rocks associated with the Section 36 garnet deposit---------------------------------- 38

46. Map of southeastern Alaska, showing the locations of onshore garnet

- - deposits------------------------------------------------------------------------------------------ 40

47. Sketch map of Alaska, showing the locations of offshore areas with possible

- - heavy-mineral potential------------------------------------------------------------------------ 41

48–50. County maps of:

- - 48. California, showing the locations of counties with garnet deposits or

occurrences--------------------------------------------------------------------------------- 42

- - 49. Nevada, showing the locations of counties with garnet deposits or

occurrences -------------------------------------------------------------------------------- 42

- - - 50. New Mexico, showing the locations of counties with garnet deposits-------------- 43

51. Maps of the Oregon coast, showing the locations of beach, offshore,

and marine-terrace deposits of black sand and offshore gold anomalies--------------- 45

Tables

- - 1. Principal garnet varieties and their characteristics----------------------------------------3

- - 2. Mineral resources of WGI Heavy Minerals, Inc.--------------------------------------------7

V


Abstract

The United States presently consumes about 16 percent 

of global production of industrial garnet for use in abrasive 

airblasting, abrasive coatings, filtration media, waterjet cutting, and grinding. As of 2005, domestic garnet production 

has decreased from a high of 74,000 t in 1998, and imports 

have increased to the extent that as much as 60 percent of the 

garnet used in the United States in 2003 was imported, mainly 

from India, China, and Australia; Canada joined the list of 

suppliers in 2005. The principal type of garnet used is almandite (almandine), because of its specific gravity and hardness; 

andradite is also extensively used, although it is not as hard or 

dense as almandite.

Most industrial-grade garnet is obtained from gneiss, 

amphibolite, schist, skarn, and igneous rocks and from alluvium derived from weathering and erosion of these rocks. 

Garnet mines and occurrences are located in 21 States, but 

the only presently active (2006) mines are in northern Idaho 

(garnet placers; one mine), southeastern Montana (garnet 

placers; one mine), and eastern New York (unweathered bedrock; two mines). In Idaho, garnet is mined from Tertiary and 

(or) Quaternary sedimentary deposits adjacent to garnetiferous metapelites that are correlated with the Wallace Formation of the Proterozoic Belt Supergroup. In New York, garnet 

is mined from crystalline rocks of the Adirondack Mountains 

that are part of the Proterozoic Grenville province, and from 

the southern Taconic Range that is part of the northern Appalachian Mountains. In Montana, sources of garnet in placers 

include amphibolite, mica schist, and gneiss of Archean age 

and younger granite. Two mines that were active in the recent 

past in southwestern Montana produced garnet from gold 

dredge tailings and saprolite.

In this report, we review the history of garnet mining and 

production and describe some garnet occurrences in most of 

the Eastern States along the Appalachian Mountains and in 

some of the Western States where industrial-grade garnet or 

its possible occurrence has been reported. Other natural and 

manmade materials compete with garnet in nearly all of the 

applications for which garnet can be used; garnet, however, 

has the advantages that it is reusable, nontoxic, and nonreactive. In addition, garnet produces much less dust than other 

abrasive materials, and spills are relatively benign and easy to 

clean up.

Introduction

Status of U.S. Industrial Garnet

Much of the following narrative is adapted from mineral 

information posted on the U.S. Geological Survey Web site 

(URL http://www.usgs.gov/), especially data from the Minerals Yearbook 1932–33 through 2005 and other sources identified in the text.

The United States currently consumes an estimated 16 

percent of global garnet production. U.S. production of industrial garnet reached an all-time high of 74,000 t in 1998 (fig. 

1), or 33 percent of global production for that year. The United 

States became a net importer of garnet in 2000, when net reliance on imports was 22 percent of apparent consumption. 

Since then, the United States has maintained its reliance on 

foreign sources of garnet to meet domestic demand. Apparent 

consumption reached a high of 83,200 t in 2003 and declined 

to 50,300 t in 2005. Imports were 60 percent of apparent consumption in 2003, 48 percent in 2004, and 40 percent in 2005 

(Olson, 2006); imports reached a high of 36,500 t in 2004 and 

decreased to 30,400 t in 2005. As of 2005, the United States 

and India were tied for greatest production capacity at 

120,000 t, followed by China (100,000 t). Australia produced 

155,000 t in 2005 (Olson, 2006), presumably a measure of 

its most recent production capacity. The Crystal Peak garnet 

(andradite and grossularite) deposit in British Columbia has a 

targeted annual production rate of 60,000 t (Grond and others, 

1991), which, if attained, would be a minimum estimate of 

Canadian production capacity.

Composition of Garnet

Several compositional schemes exist for garnet classification. In one scheme, garnets are grouped into two solidsolution series: the pyralspite series, which includes pyrope 

(Mg rich), almandite (Fe rich), and spessartite (Mn rich); and 

the ugrandite series, which includes grossularite (Ca rich), 

andradite (Ca-Fe-Ti rich), and uvarovite (Ca-Cr rich). No continuous variation in composition between members of these 

two series was considered (Winchell, 1945; Winchell and 

Winchell, 1951; Deer and others, 1967); however, some studies 

have suggested that the various members could be completely 

miscible under certain conditions (Hariya and Nakano, 1972). 

U.S. Industrial Garnet

By James G. Evans and Phillip R. Moyle
 U.S. Industrial Garnet

in a wide variety of metamorphic rocks, as well as in granites, 

pegmatites, highly siliceous volcanic rocks, and high-temperature veins. Because garnet, especially almandite, is dense and 

resists abrasion, it commonly occurs in detrital sediment, such 

as gravel and heavy-mineral sand deposits, worldwide.

Uses of Garnet

Garnet may have been used as an abrasive as early as 

1810 in the United States (see subsection below entitled “New 

York”). Garnet was first used for coated sandpaper in 1878. 

Although garnet sandpaper is still in use, the industrial technology that employs garnet has expanded to include abrasive 

airblasting, water filtration, abrasive powder, and waterjet 

cutting. Abrasive-powder uses include glass and ceramic polishing, antislip paints, and antiskid surfaces. Industrial sectors 

that utilize garnet include the petroleum and petrochemical 

industry, for cleaning pipes, secondary recovery, and oil-field 

stimulation; filtration plants; aircraft and automobile manufacturing; shipbuilding; construction and maintenance of 

structural steel and steel pipelines; painting; power generation; 

wood-furniture finishing; electronic-component manufacturing; and roughing, frosting, and engraving of glass and dimension stone. A small amount of garnet is used in wellpacks 

in deep oil wells, where temperature, pressure, and acidity 

are high. In this application, garnet sand, a porous medium, 

is forced into fractures to keep them open for enhanced oil 

recovery. By 2002, use of garnet in waterjet cutting was 

second only to its use in abrasive airblasting in the United 

States. Garnet is used in conjunction with coal and silica sand 

for filtration media that can be cleaned by backflushing. After 

backflushing, the three minerals fall back into approximately 

the same arrangement, owing to their density differences.

Other workers have suggested quasi-ternary solid solution in 

the system pyrope-grossularite-almandite-spessartite, although 

the matter was debated (see summary in Wood, 1981). A 

second classification scheme groups the four end members 

grossularite, pyrope, almandite, and spessartite, which contain 

aluminum, separately from the nonaluminous garnets andradite 

and uvarovite. A third classification scheme, used in table 1, 

describes garnet by the general chemical formula A3B2(SiO4), 

where A is such divalent metals as Ca, Fe, Mg, and (or) Mn and 

B is such trivalent metals as Al, Cr, Fe, Mn, and, in rare garnets, V, Ti, Zr, and (or) tetravalent Si (Harben, 2002). Deer and 

others (1967) pointed out that garnet species are theoretically 

possible in which divalent metals, Ca, Fe, Mg, and Mn, are 

combined with trivalent metals, Al, Cr, Fe, and Mn.

Almandite [also almandine; Fe3Al2(SiO4)3; chemical 

formulas modified from Deer and others, 1967] is the principal garnet mineral for industrial uses because of its specific 

gravity (max 4.3; Carmichael, 1989), which is higher than 

that of other garnet minerals, and its hardness (7.5–9 Mohs 

and 1,498 Knoop; Winchell, 1945; Austin, 1994b; Harris, 

2000; 7–>8 Mohs, Harben, 2002). The Knoop hardness scale 

is determined by measurement of the indentation made by 

a pyramidal diamond on a polished section of test material 

(Harben, 1978). Diamond has a hardness of 10 on the Mohs 

scale (or 40 if the scale were linear), equivalent to 8,200 on 

the Knoop scale.

Andradite [Ca3Fe2(SiO4)3], the least dense garnet mineral, 

is suitable for some industrial uses. Spessartite [Mn3Al2(SiO4)3] 

and grossularite [also grossular; Ca3Al2(SiO4)3] have also been 

included as species of industrial-grade garnet (see below). 

Andradite, almandite, and pyrope [Mg3Al2(SiO4)3] are the 

garnet minerals most likely to form gem-quality crystals.

Garnets come in every color but blue (table 1; Austin, 

1994b), and some are colorless and transparent. They occur 

Figure 1. U.S. industrial garnet production for the years 1894–2002. Data from Minerals

Yearbook 1900–2002. GARNET PRODUCTION IN TONNES

YEAR

80,000

60,000

40,000

20,000

0

189419021910191819261934194219501958196619741982

1990

1998


Recent trends in the market include an increasing demand 

for fine garnet, including micronized garnet for the electronics industry, and an increasing number of small-volume users. 

As of 2005 (Olson, 2006), major domestic end uses for garnet 

were in abrasive airblasting (35 percent), waterjet cutting (30 

percent), water filtration (15 percent), abrasive powders (10 

percent), and other uses (10 percent) (fig. 2).

Industrial Specifications

Specifications for industrial garnet are directly related to 

specific end use, and testing procedures vary widely between 

different industries. For example, Austin (1994b) and Harben 

(2002) described organizations and standards for several 

industrial garnet markets and end uses. American National 

Standards Institute (ANSI) specification B74.18–1977 

details testing methods and grading guides for grains used 

on abrasive-coated products (sandpaper). ANSI specification 

B74.12–1976 dictates the grain-size distribution and other 

qualities for abrasive use in various industrial tools, such as 

grinding and polishing wheels. Sandblasting media for U.S. 

Navy vessels must meet the standards of military specification 

MIL–A–22262(SH), including the contents of total metals and 

soluble metals, radiation, and certification by the California 

Air Resources Board (CARB), which requires all loose-grain 

abrasives used in California to be certified at the CARB testing 

facility. The CARB tests materials according to “Methods of 

Test of Abrasive Media Evaluation,” “Test Method No. 371–

A,” and its title 17, subchapter 6, entitled “Abrasive Blasting”; 

copies of these requirements are available from the CARB 

office in Sacramento, Calif. As of 1993, air-pollution-control 

agencies in Louisiana, Minnesota, and Utah had adopted the 

CARB tests and permitted only CARB-certified abrasives to 

be used in State projects requiring sandblasting. Testing procedures and standards are focused on the environmental impact 

of sandblasting abrasives, not on such qualities as cutting performance or efficiency.

The International Organization for Standardization (IOS) 

has developed specifications for the preparation of steel surfaces before application of paint and (or) related products 

(International Organization for Standardization, 1992). As of 

1996, the IOS was preparing specifications for nonmetallic 

blast cleaners that include garnet. According to their proposed 

specifications, specific gravity should range from 3.5 to 4.2, 

hardness should exceed 6.5 Mohs, moisture content should be 

Introduction

Table 1. Principal garnet varieties and their characteristics.

[Do., ditto]

Abrasive

Blasting

Waterjet

Cutting

Water

Filtration

Abrasive

Powders

Other

10

35

10

15

30

Figure 2. Pie chart showing principal domestic uses of 

garnet (in percent). Data from Olson (2005a).

Table 1

Mineral Formula Color Luster Crystal shape Specific

gravity Hardness(Mohs) Importance Solid solution

Almandite

(almandine). Fe3Al2(SiO )4 3 Dark red, brownish black---------- Transparent totranslucent,

vitreous to

resinous.

Dodecahedrons or

trapezohedrons. 4.1–4.3 7–7.5 Most importantcommercial

garnet.

Crystals contain

pyrope and spessartite molecules.

Andradite--------------- Ca3Fe2(SiO4 3) Yellowish green; greenish

brown, red-brown, dark

gray, black.

Transparent to

opaque,

vitreous to

resinous.

do ---------------------- 3.7–4.1 6.5–7 Second to almandite as a gem

variety of commercial garnet.

Crystals contain

grossularite and

(or) spessartite.

Melanite is dark

brown or black

and contains TiO2.

Grossularite

(grossular). Ca3Al2(SiO4)3 Colorless, white, gray,yellow-brown, green,

greenish brown.

– – – do ---------------------- 3.4–3.6 6.5–7 Little commercial

significance. Substitutes withandradite.

Pyrope ------------------ Mg3Al2(SiO4)3 Pink, red, crimson to black purplish red. Transparent to

translucent,

vitreous.

Rounded or embedded

 grains

3.5–3.8 6.5–7.5 Little commercial

significance

other than as an

admixture.

Normally mixes with

almandite and

grossularite.

Spessartite

(spessartine).

Mn3Al2 Black, dark red, violet-red,

brownish red, brown,

yellow-orange.

do-------------- Dodecahedrons or

trapezohedrons,

commonly striated.

3.8–4.3 7–7.5 Rare---------------------- Mixes with grossular

and andradite.

Uvarovite--------------- Ca3Cr2 Dark red, emerald green ----------- do-------------- do ---------------------- 3.4–3.8 6.5–7 do -------------------- Mixes with grossularite and andradite.

(SiO4)3

(SiO4)3
 U.S. Industrial Garnet

less than 0.5 weight percent, and content of water-soluble chlorides should be less than 0.01 weight percent. The most widely 

used particle-size grades used in blast cleaning in the United 

States are 0.1–0.3, 0.2–0.6, and 0.2–1 mm (Austin, 1994b).

No definitive method exists for testing the quality of garnet 

or any other loose-grain abrasive except by application; however, tests and examinations that can indicate a garnet’s probable abrasive performance are available. Fracture, sharpness, 

shape, and structure can be studied microscopically. Hardness 

and fragility can be evaluated by putting a sample between two 

glass slides and rubbing them together, which measures the 

relative scratch hardness of the grains and their degree of attrition (see ANSI standard B74.8.1965, “American Standard Test 

for Ball Mill Test for Friability of Abrasive Grains”). The U.S. 

National Institute for Standards and Technology has developed 

an apparatus for evaluating the abrasive quality of corundum 

that is adaptable for testing any loose-grain abrasive. Abrasive 

quality can be tested by measuring the amount of material 

removed either by weight or by volume. If it is either too hard 

or too coarse for use on a certain material, an abrasive will 

cause deep scratches that cannot be removed by subsequent 

finishing. If it does not have a proper grain shape or does not 

maintain sharpness during breakdown, an abrasive may burn or 

gouge the material being abraded.

 The American Water Works Association (AWWA) has 

established specification B100–89, “Standards for Filtering 

Materials,” which did not cover such high-density media as 

garnet and ilmenite as of 1993 (Austin, 1993b), although the 

AWWA planned to include garnet and ilmenite in an updated 

version. Specifications for garnet would include particle shape, 

specific gravity, effective grain size, coefficient of grain-size 

uniformity, content of acid-soluble impurities, and radioactiveor heavy-metal content.

Ives (1990) developed procedures to test the qualities of 

filtration media, including effective size (sieve size at which 

10 percent of the weight is finer), uniformity coefficient (sieve 

size at which 60 percent of the weight is finer), specific gravity 

(1.4–3.9), settling rate at 20oC, hardness (>2 Mohs), sphericity (0.65–0.85), acid solubility (<5 percent), and resistance to 

attrition (weight loss, <5 percent). The most common particlesize grades of garnet used for water filtration in the United 

States are 0.25–0.71, 0.3–0.84, and 1.41–4.75 mm (Austin, 

1994a); garnet finer than 0.3 mm across is generally used in 

pressure-filtration systems. For additional information on 

industrial-standards organizations and on product specifications for industrial garnet, see Harben and Kuzvart (1996) and 

Harben (1999, 2002).

KTA-Tator, Inc. (URL http://www.kta.com/services), tests 

garnet and other abrasives for the AWWA and the Society for 

Protective Coatings (SPC, as of 1997; URL http://www.sspc.

org/about/; founded as the Steel Structures Painting Council 

in 1950), which also provides comparative tests of garnet and 

other abrasives to determine whether they meet military specifications, how clean the abrasives are, how well they clean, 

their extent of degradation during use, and other qualities. The 

SPC, which is part of the Carnegie Mellon Research Institute, 

conducts its research carefully so as not to favor one abrasive 

manufacturer over another, because their representatives may 

be SPC members. Other abrasive-testing companies are Flow 

International Corp., Ingersoll Rand, and Jet-Edge, Inc.

Nearly all the grade-grain garnet processed for use as 

abrasive coatings is heat treated. Impurities picked up during 

processing generally stick to the garnet and may decrease its 

cleanliness and capillarity needed for adhesion to bonding 

agents. Investigations in the 1960s determined that heat treatment could clean garnet but that too high a temperature can 

damage its abrasiveness. In the mid-1960s, the abrasive-coating industry accepted uniform color standards that ensured 

the cleanliness of garnet surfaces; the standard color closely 

approaches the natural color of abrasive garnet.

In waterjet cutting, garnet grains are entrained in a highvelocity stream of water that impacts the material to be cut at 

high pressure (345 MPa). Waterjet cutting is most commonly 

used for inflammable materials, such as in oil refineries, but 

also for underwater steel structures and for shaping such materials as marble, granite, automotive glass, textiles, plastics, 

aluminum, and high-strength steel. Garnet for this use needs 

to be especially hard, such as almandite, with sharp, angular 

cutting edges. For ductile materials, softer and less expensive 

abrasives, such as slag, may be better than garnet (O’Driscoll, 

1993). Garnet as coarse as 1 mm across is favored for cutting 

steel. For most other cutting, 0.18–0.25 mm (60–80 mesh) is 

the most popular particle-size grade, accounting for 90 percent 

of the garnet used in waterjet cutting in the United States 

(Austin, 1994b).

Evaluation of Garnet Deposits

Evaluation of garnet deposits to determine their suitability 

for industrial production includes the following factors: size and 

grade of reserves, mining conditions, garnet quality, location 

of the deposit relative to markets, and milling costs. Reserves 

should contain a minimum of 2 million t of ore with a cutoff 

grade of about 20 weight percent garnet. Various environmental, social, and physical factors can preclude mining, such 

as proximity to houses, historical sites, national monuments, 

archeologic or paleontologic sites, wildlife refuges, and municipal watersheds, and may include local zoning regulations, environmental regulations, and configuration and structure of the 

deposit. After initial crushing, almandite or almandite-pyrope 

should be present as fine- to coarse-grained discrete crystals that 

are free of such inclusions as quartz, mica, hornblende, feldspar, and alteration products. As discussed below, andradite and 

grossularite also have their uses but are inferior to almandite in 

specific gravity and hardness. The specific gravity and hardness 

of the garnet should be uniform, and the crystals should not be 

highly weathered or friable. Any cleavage within the garnet 

should be evaluated for its distribution in the deposit and its 

effect on product quality. If the deposit is not near major market 

areas, it must be near adequate inexpensive transportation; railways or waterways are preferred. The deposit should also be 

reasonably accessible by road. An ideal ore contains garnet that 


can be liberated with minimum crushing and recovered by gravity/density-based methods of mechanical concentration. Portions of the concentrate may have to be ground to smaller grain 

sizes in order to obtain garnet of appropriate purity.

Markets for Garnet

Domestic garnet consumption is estimated to have 

decreased from 83,200 t in 2003 to 58,600 t in 2004, and to 

50,300 t in 2005, or by 40 percent since 2003 (Olson, 2006). 

The high in apparent consumption in 2003 was assumed to be 

cent of global production. Global production of 312,000 t in 

2005 (Olson, 2006), if consumed, indicates that worldwide 

use of industrial garnet has increased 39 percent since 1998 

(224,000 t).

The United States currently exports more than 10,000 

t of garnet per year (11,000 t in 2003, 10,900 t in 2004, and 

13,300 t in 2005; Olson, 2006), most of which comes from 

New York and has special fracture characteristics. The garnet 

breaks down during use but fractures along a cleavage that 

preserves sharp cutting edges of the grains. The U.S. began 

exports of 10,000 t or more annually in 1996, and did so sporadically before then.

Introduction

—

—

—

—

G

ARNET

VALUE IN

D

OLLARS

A

N

D

U

NIT

VALUE IN

D

OLLARS PER T

O

N

NE

Figure 3. U.S. garnet value and unit value for the years 1900–2000, plotted using raw dollar value (not 

based on 1998 dollar values). Data from industrial garnet statistics, 1900 through 2000; last modified 

April 17, 2003.

Abrasive

Blasting

60

Waterjet

Cutting

20

Water

Filtration

10

Other

10

Figure 4. Pie chart showing principal uses of garnet (in 

percent) worldwide. Data from Olson (2004).

a result of lower prices for stock sales from Patterson Materials 

Corp. and cheap imports.

The price of industrial garnet varies widely, depending 

on its type, source, quantity purchased, and end use (fig. 3). In 

2004, the price for most crude concentrates ranged from $50 to 

$150 per tonne, and prices for most refined garnet from $60 to 

$450 per tonne (Olson, 2004a, 2006; $300–600 per tonne for 

garnet used in waterjet cutting; Grond and others, 1991).

In 2003, principal garnet uses worldwide were abrasive 

blasting, 60 percent; waterjet cutting, 20 percent; filtration 

media, 10 percent; and other uses, 10 percent (fig. 4; Olson, 

2004). Global garnet production in 2005 was estimated at 

312,000 t from Australia, Canada, China, India, and the 

United States (Olson, 2006; Gorill, 2003, estimated 440,000 

t for 2003). Domestic garnet production was 28,400 t, or 

about 9.4 percent of global production, in 2004, in contrast to 

74,000 t, or 33 percent of global production, in 1998, when 

domestic garnet production peaked; estimated production in 

2005 was a little less than in 2004 (Olson, 2006), or 9.1 per-
 U.S. Industrial Garnet

The U.S. garnet industry must compete with foreign suppliers that have extremely large, easily and cheaply mined 

garnet deposits. The largest garnet producers in Idaho and New 

York have become parts of international corporations (Barton 

Mines Co., LLC, and WGI Heavy Minerals, Inc.; see below), a 

move that may soften the economic impact of imports, at least 

for these two companies, although problems affecting production abroad may arise in foreign operations (see below).

Garnet resources are known in Australia, Canada, Chile, 

China, the Czech Republic, India, Norway, Pakistan, Portugal, 

Russia, South Africa, Spain, Sri Lanka, Thailand, Turkey, and 

the Ukraine. The first recorded U.S. import of industrial garnet 

was from Spain in 1910. Imports of industrial garnet have 

principally been from Australia, China, India, and, recently, 

Canada. Since 2000, the United States has been a net importer 

of garnet (Austin, 2002a, 2003a, 2004, 2005a, 2006). Of the 

garnet imported from 2001 to 2004, 39 percent was from Australia, 26 percent from India, 18 percent from China, 12 percent from Canada, and 5 percent from other countries (Olson, 

2005a, 2006). At present, natural garnet, emery, natural corundum, and other natural abrasives, including abrasive coatings, 

are imported duty free.

International Garnet Reserves

In 2004, the United States had estimated garnet reserves 

of 5 million t and a reserve base of 25 million t (Olson, 2006). 

Large domestic garnet resources are concentrated in coarsely 

crystalline gneiss, schist, and granite in Maine, New Hampshire, eastern New York, and North Carolina. Garnet placers 

are important in Idaho, Montana, North Carolina, and Oregon. 

Garnet mined in southwestern Montana in 1996–2002 was from 

dredge tailings and saprolite; production in 2005 was from placers. Skarn deposits in southwestern New Mexico contain abundant garnet, some of which may be economic to mine, although 

a recent study of recovery of garnet in mill tailings (Cetin and 

others, 1996) was disappointing. In comparison, according to 

Olson (2006), Australia, the world’s largest garnet exporter, has 

reserves of more than 1 million t and a reserve base of 7 million 

t; China has estimated moderate to large reserves and reserve 

base; India has official reserves of 90,000 t and a reserve base 

of 5.4 million t; and all other countries combined have total estimated reserves of 6.5 million t and a reserve base of 20 million t 

(Olson, 2006).

Canada has garnet deposits in British Columbia, Labrador, Manitoba, New Brunswick, Newfoundland, Nova Scotia, 

Ontario, and Quebec (Harben and Kuzvart, 1996). Garnet 

deposits in the Sudbury area, Ontario, and in Labrador, Newfoundland, Nova Scotia, and Quebec consist largely of almandite in high-grade regionally metamorphosed rocks, with garnet 

grades ranging from 15 to 100 weight percent. Garnet deposits 

(andradite and grossularite) in western Canada are mostly 

in skarns. One of these deposits, the Crystal Peak deposit on 

Mount Riordan, British Columbia, has at least 40 million t of 

reserves containing 80 volume percent garnet (andradite and 

grossularite; Grond and others, 1991; Mathieu and others, 1991) 

and an additional 60 million t of “geological” reserves (garnet 

content not indicated); total Canadian garnet reserves are probably much larger.

Australian and Indian garnet resources are overdue for a 

reevaluation. In 1997, one Australian garnet mine, GMA Garnet 

Pty Ltd. (formerly Target Mines Ltd.?; Austin, 1993b), a joint 

venture between the Barton Mines Co., LLC, in the United States 

and Hancock and Gore Ltd. (currently HGL Ltd.) in Australia, 

reported proven reserves of 4 million t and probable reserves 

much higher in high-grade placers in dunes (avg 23 weight percent garnet) that extend for about 12 km along the Australian 

coast at Port Gregory, 100 km north of Geraldton in Western Australia (Kendall, 1997; Harben and Kuzvart, 1996). In addition, 

GMA secured mining rights to probable reserves of about 16.9 

million t of heavy-mineral-bearing alluvial sand averaging 19.5 

weight percent heavy minerals of which almandite composes 90 

percent; the remaining 10 percent is ilmenite, quartz, and zircon. 

Annual Australian garnet-production capacity has increased to 

155,000 t (Olson, 2006), close to half of which may be from 

GMA. As of 1997, this garnet was used mostly for abrasive blasting; polishing powders, filtration media, and waterjet cutting 

account for smaller sales. Australia supplies the most popular size 

class of garnet exported to the United States for abrasive blasting 

(particle-size grade, 0.25–0.59 mm; Austin, 1993b).

Descriptions of the extensive garnet beach sands in southeastern India (table 2; WGI Heavy Minerals, Inc., 2002) suggest 

that India’s recognized reserves (90,000 t) and reserve base (5.4 

million t) are underestimated. WGI Heavy Minerals, Ltd., the 

parent entity of the Emerald Creek Garnet Co. in Idaho, has a 

subsidiary, Transworld Garnet India Pvt. Ltd., with lease areas 

estimated to contain resources of more than 10 million t of 

garnet. From April 1997 to December 2003, Transworld produced 258,000 t of almandite (annual production rate, approx 

38,680 t; WGI Heavy Minerals, Inc., 2004). At that time, WGI 

anticipated a buildup to an annual production of 140,000 t of 

garnet, 140,000 t of ilmenite, 12,000 t of zircon concentrate, 

and 4,500 t of rutile from its Indian operations—a projection 

that would approximately double annual Indian garnet production, according to Roskill Information Services, Ltd. (2000), but 

triple it according to the smaller estimate (65,000 t for 2005) by 

Olson (2006).

In general, the garnet market is highly competitive, and so 

producers need to minimize production costs and develop the 

deposits from which garnet is produced in combination with 

other minerals (ilmenite, zircon, sillimanite, kyanite, staurolite). 

These conditions can be met in the beach deposits of southeastern India that are mined by government-mandated hand methods and hand loading of dump trucks (hoe and headbasket), 

among other stipulations (WGI Heavy Minerals, Inc., 2004).

Risks of Production Abroad

Unforeseen difficulties have cut into Transworld Garnet 

India Pvt. Ltd.’s production plans, illustrating some of the 


risks that may curtail foreign garnet production. In 2002, 

because of the delay in bringing micronized garnet to market 

by way of its joint-venture plant in Chennai, India, over a 

2-year period and small market demand, Transworld wrote 

off $580,000 in net expenditures connected to the plant (WGI 

Heavy Minerals, Inc., 2003). More serious issues (WGI 

Heavy Minerals, Inc., 2005b, c) include lease applications, 

manufacturing processes, unanticipated legal complexities in 

governmental processes, resolution of generations of undocumented ownership on numerous parcels of land, export 

permit, and increased professional fees related to a review 

of their Indian operations. All of the above-mentioned legal 

obstacles were believed to have been resolved in 2002 (WGI 

Heavy Minerals, Inc., 2003), clearing the way for Transworld 

to produce and export garnet. According to WGI, lack of 

reasonable and timely solutions to these difficulties in India 

may require Transworld to write off their substantial assets in 

Tamil Nadu and Andhra Pradesh.

Garnet resources that are also known in Sri Lanka have 

been pursued by WGI Heavy Minerals, Inc. After a late 2001 

ceasefire between government forces and separatists in Sri 

Lanka, a 50-percent subsidiary of WGI received environmental clearance for the development of heavy-mineral deposits 

(garnet, ilmenite, rutile, and zircon; Kuo, 2002). Plans for 

2002–3 included conversion of mining leases into permits, 

development of a mining program, and drilling of new areas 

for heavy minerals. WGI’s operation received a 10-year 

mining lease on a heavy-mineral deposit at Hambantota on 

the southeast coast (Kuo, 2004), and an independent technical 

report was planned for early 2005. Some of the legal issues 

that Transworld encountered in India are also present in Sri 

Lanka (WGI Heavy Minerals, Inc., 2005b). In addition, as a 

result of the December 2004 tsunami that struck the coast of 

Sri Lanka, the Coastal Conservation Department asked the 

WGI subsidiary not to mine the dunes on their mineral leases 

(WGI Heavy Minerals, Inc., 2005c), and so WGI’s Sri Lankan 

project is in doubt.

Competition from Other Natural and Manmade 

Abrasives

U.S. garnet has to compete with various natural and manmade abrasives for its share of the domestic abrasives market. 

Some materials compete with garnet but entail sacrifices in 

quality or cost. For abrasive airblasting, competing materials 

include fused alumina, Si carbide, steel shot, specular hematite, 

magnetite, silica sand, coal boiler slag, metallic slag, staurolite, corundum/emery, diatomite, feldspar, nepheline syenite, 

olivine, perlite, and ilmenite. For abrasive coatings, competing 

materials include fused alumina, Si carbide, and corundum. For 

waterjet cutting, competing materials include alumina, olivine, 

and several manmade materials. Precision abrasive powders, 

other than garnet, include Ce oxide, diamond, fused alumina, 

Si carbide, pumice, and tripoli. Filtration media, in addition to 

garnet, include activated carbon/anthracite, asbestos, cellulose, 

diatomite, ilmenite, magnetite, olivine, perlite, pumice, silica 

sand, and plastics. Effective backflushable filters use garnet, 

silica sand, and anthracite together. Diamond, corundum, and 

fused alumina compete in lens grinding and many lapping 

operations. Quartz sand, Si carbide, and fused alumina compete 

in finishing of plastics, wood furniture, and other products. For 

nonskid surfaces, competing materials include alumina, emery, 

and silica sand. Oil-well gravel packs can be made from calcined bauxite instead of garnet (Harben, 2002). The most commonly used abrasive in the United States as of 2001 is silica 

sand, followed by coal boiler slag (fig. 5). Garnet made up only 

2 percent of the domestic abrasives industry then, and its usage 

has shown no sign of increasing substantially.

Advantages of Garnet

Garnet has many advantages that may not have been 

fully exploited industrially. For example, garnet is free from 

toxic elements and chemically inert. Airblasting with garnet 

Introduction

Location Garnet Ilmenite Rutile Zircon Sillimanite

Benewah County, Idaho1 ------- 527 – – – – – – – –

Tamil Nadu, India1 -------------- 1,105 168 – – – – – –

Andhra Pradesh, India2 --------- 38,636 34,853 4760 4170 54,830

Total -------------------------- 10,268 5,021 760 170 4,830

1

DDH Geomanagement Ltd. resource estimate. 2

Reserve/resource value based on data from drilling to a depth of 2.9 m over an 11.2-km2

area, representing less then 15 percent of mineral properties under existing or pending leases. 3

Strathcona Mineral Services Ltd. resource estimate. 4

Reserve/resource value based on data from drilling to a depth of 2.9 m over an 11.2-km2

area.

5

Internal calculation based on resource estimate; currently no market value.

Table 2. Mineral resources of WGI Heavy Minerals, Inc.

[All values in thousands of tonnes]
 U.S. Industrial Garnet

produces less dust than with silica sand, which can cause silicosis and cancer—unless, of course, siliceous rock is being 

blasted. Slag can also be a potential source of toxic heavy 

metals (Grond and others, 1991). Low concentrations of dust 

allow operators of airblasting equipment to have a relatively 

unimpeded view of the target. Garnet is nontoxic if released, 

and no special equipment or precautions are required in managing a release unless the garnet was contaminated during use. 

In comparison with silica sand, which currently is the most 

commonly used abrasive in the United States, garnet requires 

a smaller storage area because less abrasive is needed to do 

the same job and garnet is not hygroscopic. Garnet can also 

provide greater cutting speed (Crandall, 1950). Hauling and 

removal of garnet and residue may be less costly than disposal 

of silica sand; however, volumetric considerations may be 

offset by the density of garnet. Some garnet can be recovered 

and reused as many as eight times; recycling systems are 

available that separate usable >100-mesh garnet from sludge 

and prepare the garnet concentrate for reuse (for example, 

Jet-Edge, Inc.; URL http://www.jetedge.com/products/abrecycling.html). Recycling could negatively impact domestic 

markets if recycled garnet substitutes for newly mined garnet. 

At present, however, only a small amount of garnet is recycled 

(Olson, 2006). In addition, garnet characteristics can be tailored to end use. Many of these characteristics make garnet 

a tool that can improve production and safety on the job and 

potentially lower disposal costs.

U.S. Garnet Deposits

Overview

The purpose of this report is to describe the status of U.S. 

industrial garnet deposits, their locations, history, and market 

forces. Information for parts of the following text is from the 

Minerals Yearbook 1931–32 through 2005 (Hatmaker and 

Davis, 1933; Bowles and Davis, 1934; Davis, 1935; Johnson 

and Davis, 1936, 1937; Johnson and Shauble, 1939; Metcalf, 1940, 1941, 1943a, b, 1949, 1950, 1951; Metcalf and 

Cade, 1945, 1946; Metcalf and Holleman, 1948; Chandler 

and Tucker, 1953, 1958a–d, 1959, 1960, 1961; Chandler and 

Marks, 1954, 1955, 1956; Cooper and Tucker, 1962, 1963; 

Ambrose, 1964, 1965, 1966; U.S. Bureau of Mines staff, 1967, 

1981, 1987, 1993–94a, 1993–94b, 1995; Cooper, 1968; Wells, 

1971; Clarke, 1972, 1973, 1974, 1975, 1976, 1977; Adams, 

1978, 1980; Baskin, 1980; Smoak, 1982, 1983, 1984, 1985; 

Austin, 1988, 1989, 1990, 1991a, b, 1992, 1993a, b, 1994a, 

b; Balazik, 1995a, b, 1996, 1997a, b, 1998, 1999, 2000a, b; 

Harben and Kuzvart, 1996; U.S. Geological Survey, 1997, 

2000, 2001, 2002a, b, 2003, 2004, 2005a–d; Harben, 1999, 

2002; Olson, 1999, 2000, 2001a–c, 2002a, b, 2003a, b, 2005a, 

b, 2006).

Garnet deposits occur in Alaska, Arizona, California, Colorado, Connecticut, Georgia, Idaho, Maine, Montana, Nevada, 

New Hampshire, New Mexico, New York, North Carolina, 

Oregon, Pennsylvania, South Carolina, Tennessee, Utah, 

Vermont, and Virginia. As of 2005, four mines were in operation for industrial-grade garnet: one in northern Idaho, one in 

southwestern Montana, and two in New York.

The single most consistent U.S. producer of almandite is 

the Barton Mines Co., LLC, in Warren County, N.Y. Andradite has been produced as a byproduct of wollastonite mining 

from 1952 to 2005, most recently by NYCO Minerals, Inc., 

in Essex County, N.Y. The International Garnet Abrasive 

Co. Inc. in Clinton County, N.Y., processes and sells all the 

garnet produced by NYCO. The formerly active mine of Patterson Materials Corp. in Dutchess County, N.Y., was closed 

in 2002, but the company continued to sell stockpiled garnet. 

The Emerald Creek Garnet Co. (formerly Garnet Mines, Inc.) 

in Benewah County, Idaho, has produced garnet continuously 

since production began there in 1940. Garnet was produced 

from Idaho black sand placers in central Idaho from 1952 to 

1966. One or more garnet-producing mines have been located 

in other States: New Hampshire, from 1928 to 1939, was the 

leading U.S. garnet producer of the 1930s; Vermont, from 

1939 to 1941; Maine, from 1978 to 1988; Connecticut; and 

North Carolina, most recently the Celo Mines, with garnet 

production from 1936 to 1944 incidental to mining kyanite. 

Florida produced ilmenite from polymineralic beach and dune 

sand from the mid-1940s to the present, and garnet in 1952–55 

and 1957. Garnet was mined sporadically in southwestern 

Montana in the 1990s through 2005. At present, garnet mines 

and occurrences in other States, including Alaska, Arizona, 

1

2

3

4

5

6

7

Silica Sand

Coal Boiler

Slag

Steel

Abrasives

Copper-Nickel

Slag

Staurolite,

Olivine,

and Other Minerals Garnet

24

56

10

4

4 2 _

-

-

Figure 5. Pie chart showing U.S. abrasive-mineral demand (in percent) for the year 2001.
U.S. Garnet Deposits 

California, Colorado, Nevada, Pennsylvania, South Carolina, 

Tennessee, Utah, and Virginia, have largely been exploited for 

mineral specimens and gem stones.

New York

Geologic Setting

Currently, all active garnet mines in the Eastern United 

States are in eastern New York in the eastern Adirondack 

Mountains and the southern Taconic Range of the northern 

Appalachian Mountains. The oldest rocks in the Adirondacks 

are 1.6- to 1.9-b.y.-old anorogenic anorthosite, charnockite, 

and related rocks, the protoliths of which are interpreted as a 

bimodal caldera complex (McLelland, 1986). From 1.1 to 1.0 

Ga, these rocks were affected by the widespread Grenville 

orogeny, which recorded closure of an ocean basin, subduction, crustal thickening, compression, and metamorphism 

(McLelland and Isachsen, 1985, 1986; McLelland and others, 

1988, 2001). Smaller slices of similar rock occur along the 

crest of the Appalachian Mountains from central Vermont to 

east-central Alabama (fig. 6; Rankin and others, 1989a).

Bohlen and others (1980) drew isotherms, defined by the 

feldspar and coexisting Fe-Ti oxide geothermometer, for the 

Adirondack Mountains. Peak temperatures were 700–760oC in 

most of the Adirondack Highlands and 750–800oC in the High 

Peaks area during Grenville metamorphism. The active garnetproducing mines are in the eastern Adirondacks within a zone 

where maximum temperatures ranged from 650oC to 770oC.

The three quarries formerly operated by Patterson Materials Corp. are in the southern part of the Taconic Range, east 

of the Hudson River, in southeastern New York. Barth (1936) 

published an early account of these metamorphic rocks in 

Dutchess County. The Taconic Range is described in the subsection below entitled “Northern Appalachian Mountains and 

New England.”

Barton Mines Co., LLC

The following narrative is adapted from the reports by 

Harben (1978), Dickson (1982), Kendall (1992), the Minerals 

Yearbook, and other sources cited in the text.

The Barton Mines Co., LLC (most recent name), has 

mined almandite-pyrope garnet continuously since 1878. 

Its first garnet mine was at Gore Mountain, 5 km west of 

the town of North Creek in Warren County (fig. 7). In 1912 

and 1922, the mine was called the Rogers Mine (Miller, 

1912; Ladoo, 1922). In 1982, the mine at Gore Mountain 

closed, and the company moved its mining operations to 

Ruby Mountain, 8 km northwest of Gore Mountain (Kelly 

and Peterson, 1993) in northern Warren County. The garnet 

has a cleavage along which the grain breaks under stress; the 

cleavage is maintained after fracturing, so that the residual 

garnet retains its sharpness (fig. 8). This property makes the 

garnet especially suited for abrasive coatings. Because of 

its physical properties (hardness, structure), the garnet is in 

demand outside of North America (>10,000 t/yr). The Gore 

Mountain Mine is now the site of Garnet Mine Tours (URL 

http://www.garnetminetours.com/), which also features a 

shop containing a mineral collection and providing gemcutting demonstrations.

The Gore Mountain ore body was about 2 km long by 

15 to 90 m wide and dipped 7–9o W. The garnet grade was 5 

to 20 weight percent, averaging less than 10 weight percent 

(Harben and Kuzvart, 1996), although a published photograph (fig. 9) suggests that the average grade in the past may 

have been higher. Proposed geologic models include contact 

metamorphism of an olivine gabbro by a pretectonic syenite 

(Levin, 1950), prograde metamorphism (Bartholome, 1960), 

and localized influx of water at the margin of a competent 

metagabbro during amphibolite-facies metamorphism (Goldblum, 1988; Goldblum and Hill, 1992).

The Ruby Mountain Mine is in gabbroic gneiss (W.M. 

Kelly, written commun., 2003). The ore contains 5 to 15 

weight percent garnet porphyroblasts, as much as 4 cm across, 

with the same type of cleavage as the garnet in the Gore 

Mountain pit (fig. 10). The amount of recoverable high-quality garnet on Ruby Mountain is estimated at 0.6 million t. The 

rock is mined by surface methods. The markets served by the 

Barton Mines Co., LLC, are, in decreasing volume, waterjet 

cutting, lapping television glass, finishes, and abrasive coatings; abrasive airblasting and filtration media are minor. In 

addition to industrial garnet, the attractive Garnet Gem Granite 

(garnetiferous granite) on Ruby Mountain is being quarried for 

polished slabs for heavily used surfaces, such as countertops 

and flooring. The granite contains deep-red garnets, 2 to 20 

mm across, in a background of pale-green epidote or pyroxene 

or white feldspar and black hornblende; several color variations are available (URL http://www.bartonquarries.com/). The 

Garnet Stone Co. is mining the same granite near Lake Placid 

in northwestern Essex County for slabs for countertops, tabletops, tile, fireplaces, and landscaping.

The processes used by Barton Mines to produce industrial garnet were evolved from experience and improvements 

in technology. In 1924, Barton Mines constructed the first 

processing plant in which separation was done by jigs. In 

1941, heavy-media separation was added; and in 1945, flotation. Currently, the ore is crushed and screened to a grain size 

of 3.36 to 3.38 mm, and the coarse fraction goes to a heavymedia circuit with a specific gravity of 3.02 for a second 

separation. This screened fraction goes to a flotation circuit, 

where it is first ground to a grain size of 0.3 mm in ball mills 

and then fed to flotation cells. The concentrate from the 

heavy-media circuit is roll-crushed, combined with float concentrate, dried, and heat-treated in a rotary kiln.

The garnet from Barton Mines supplies 10 plants that 

produce abrasive-coated papers and cloths: 2 each in New 

York and Virginia, and 1 each in Massachusetts, Michigan, 

Minnesota, Mississippi, Ohio, and Pennsylvania. Barton also 

provides most or all of the garnet for export (13,300 t in 2005).
10 U.S. Industrial Garnet

Figure 6. Sketch map of the Appalachian Mountains and New England, showing areas of basement rocks of the Proterozoic (Laurentian) continental margin and adjacent suspect terranes 

(adapted from Rankin and others, 1989a).
11

NYCO Minerals, Inc.

NYCO Minerals, Inc. (URL http://nycominerals.com/), 

a subsidiary of Fording Canadian Coal Trust (as of 2003; 

URL http://fording.ca/; formerly Fording Coal Ltd., with 

headquarters in Calgary, Alberta, Canada; W.M. Kelly, written commun., 2003), mines wollastonite (CaSiO3

; Deer and 

others, 1967) near Willsboro in Essex County, on the west 

side of Lake Champlain, producing andradite as a byproduct. 

The wollastonite deposit was discovered in 1810, before the 

mineral had been named. The deposit was initially mined for 

its garnet and not for wollastonite until 1936. The foregoing information suggests that garnet was used in the United 

States, probably as some form of abrasive, before its first use 

in sandpaper in 1878—possibly as early as 1810. The success 

of research on the uses of wollastonite at New York State College attracted the attention of Godfrey L. Cabot (Inc.), who 

purchased the original wollastonite deposit in 1951. Processing facilities were built within 2 years, and the product was 

sold under the trade name Cab-O-Lite. In 1969, the operation 

was sold to Interpace Corp. of New Jersey. Recognition of 

the lung disease asbestosis in the early 1970s led to increased 

sales of wollastonite, which was used in calking, sealants, 

joint cement, roofing, plastics, and other products for which 

asbestos had previously been used. In 1979, the operation was 

sold to Processed Minerals, Inc., which later became known 

as NYCO Minerals, Inc., a subsidiary of Fording Coal Ltd. 

of Alberta, Canada. Fording began managing the operation in 

1989 and later bought it. Today, NYCO’s wollastonite is used 

principally for ceramic tile, porcelain, and paint extender, in 

reinforcement fibers for friction materials and plastics, and in 

metallurgy.

U.S. Garnet Deposits

Figure 7. County map of New York, showing county boundaries and locations of counties (names in all caps) with deposits of garnet 

(Gar) and associated sand and gravel (SG) and wollastonite (Wol). In Dutchess County, sand and gravel includes crushed garnetiferous metamorphic rocks that are processed for andradite. Dots, cities and towns; star, State capital.

CLINTON

Niagra Falls

Ithaca

Gar

SAINT

LAWRENCE

ESSEX

SG

WARREN

WASHINGTON

KINGS (BROOKLYN) RICHMOND

(STATEN ISLAND)

DUTCHESS

 SG

Wol

Gar

Albany

White Plains

New York City

Syracuse

0 50 Kilometers
12 U.S. Industrial Garnet

The NYCO ore body is in a belt of wollastonite-bearing 

rocks, about 10 km long by 0.4 km wide. The largest zone 

of wollastonite within the belt ranges from 9 to 20 m thick, 

averaging 13 m. The wollastonite is intercalated with zones 

of andradite and Fe-rich diopside, both of which compose 10 

to 20 weight percent of the ore. The ore at the Willsboro Mine 

in Essex County consists of as much as 60 weight percent 

wollastonite, with a mix of andradite, grossularite, and diopside. The ore is transported 22 km to NYCO’s plant, where 

beneficiation of the wollastonite-garnet ore is in two stages. 

In the first stage, the ore is dried, crushed, screened, and then 

recrushed to a grain size of 1.19 mm; in the second stage, the 

ore passes over a series of screens for grain-size splits.

NYCO produced both refined garnet for use in abrasive 

airblasting and water filtration, and crude concentrate for 

further refining. In earlier operations, magnetic separators 

removed the garnet from the grain-size fractions. Four grain 

sizes of garnet concentrate were bagged for shipment. At 

present, NYCO electrostatically separates wollastonite and 

sells the tailings to Virginia Materials, Inc. (formerly International Garnet Abrasives Inc.), a division of Stake Technology, 

Ltd. Virginia Materials concentrates the garnet from tailings 

at its processing plant in Plattsburg in Clinton County and 

produces garnet that is a mix of andradite and grossularite; 

the crude concentrate may contain the pyroxenes diopside 

[CaMg(SiO3)2] and hedenbergite [CaFe(SiO3)2; chemical formulas modified from Deer and others, 1967].

Other Garnet Mines and Deposits

Patterson Garnet Corp. (formerly Patterson Materials 

Corp.; URL http://www.peckham.com/), a subsidiary of 

Peckham Industries, Inc., produced almandite as a byproduct 

of its construction-aggregate operations in mica-garnet schist. 

Peckham Industries was founded in 1924 by William H. Peckham, who began business as a highway contractor. Acquisition 

of aggregate facilities provided material support for highway 

construction. In 1968, the company changed its focus from 

highway construction to highway-building materials. PatterGarnet

Plagioclase

Hornblende

Amphibolite

Figure 8. Garnet porphyroblast in the Gore Mountain deposit, N.Y., 

showing typical cleavage. Photograph courtesy of W.M. Kelly, New 

York Geological Survey.

Figure 9. Garnet ore in the Gore Mountain deposit, N.Y. (Levin, 1950).

Figure 10. Garnet ore in the Ruby Mountain deposit, N.Y. Photograph 

courtesy of W.M. Kelly, New York Geological Survey.
13

son Garnet Corp. operated aggregate quarries in Wingdale in 

Dutchess County, in the town of Patterson in Putnam County, 

and in Easton in Washington County; the quarry in Dutchess 

County is the one associated with garnet in the literature. As of 

2002, production of byproduct almandite ceased, and the company began selling off its stock of garnet.

Patterson’s almandite is especially hard, rated at 1,498 

on the Knoop scale. In 2002, Patterson supplied 16- to 32-

mesh garnet to WGI Heavy Minerals, Inc., to blend with 

their product from Emerald Creek, Idaho (Harben, 2002). 

In 2003, Patterson produced 50-, 80-, and 100-mesh garnet 

for the waterjet-cutting industry, its chief customers (URL 

http://www.peckham.com/); presumably, these garnet sales 

were from the company’s stock.

Garnet ore similar to that at Gore Mountain (figs. 8, 9) 

was mined at the Hooper Mine, a quarry operated by the North 

River Garnet Co., about 5 km southwest of the town of North 

River in Warren County (Ladoo, 1922; Miller, 1938; Jensen 

and Bateman, 1981), about 1 km south of the Warren-Essex 

County line. When Ladoo examined the property, he considered this mine to be the principal garnet mine in the area. The 

ore was garnetiferous gneiss that contained almandite crystals, 

as much as 12 cm across but averaging less than 2 cm across. 

Garnet content averaged no more than 8 weight percent. The 

ore body was described as very large. By 1937, the Hooper 

Mine had been inactive for many years (Miller, 1938).

The Sanders Brothers deposit is on the north side of Mill 

Creek, about 3 km south of Riparius in Warren County (Ladoo, 

1922). The deposit was operated on a small scale around 1922 

by Warren County Garnet Mills. The ore was in a narrow band 

of light-red garnet and green pyroxene within fine-grained 

gneiss. Locally, the garnet occurred as nearly pure nodules. The 

garnet lacked cleavage and broke into irregular grains.

Garnet was mined on the northwest side of Humphrey 

Mountain in Warren County, about 13 km southwest of North 

Creek, before 1937 (Miller, 1938). The ore was mined along 

the contact between syenite and gabbro. The garnet porphyroblasts resembled the garnets at Gore Mountain (fig. 8) in 

having coronas of amphibole.

The Crehore Mine in Essex County, about 9 km northwest 

of North River, was operated by the American Glue Co. when 

Ladoo (1922) examined the property. The garnet occurred in a 

band of hornblende gneiss, about 13 m wide. Garnets, as much 

as 20 cm across, are in a black hornblende matrix, resembling 

the ore at Gore Mountain.

Other garnet deposits that were mined include those 

on Oven Mountain in Warren County, about 6 km south of 

North Creek (Miller, 1938); at a site a few kilometers south 

of Keeseville in Essex County; at the Rexford Mine, about 

2 km south of North Creek; at the Parker Mine, southwest 

of Dagget Pond and about 7 km northwest of Warrenburg in 

Warren County; and at the Amasa Corbin Mine, about 5 km 

north of the town of Gouverneur in St. Lawrence County 

(Ladoo, 1922). At the Rexford Mine, garnets as large as 12 

cm across occurred in small altered lenses of metagabbro 

within gneissic syenite (Miller, 1938).

The locations of both active and inactive mines suggest 

that significant garnet deposits are relatively common in the 

Warren-Essex County area, which thus contains a substantial part of the U.S. reserves and reserve base of garnet (see 

above). New York is one of the few States with high-quality 

garnet reserves suitable for abrasive coatings.

Garnet was designated the official New York State gem 

stone in 1969.

Northern Appalachian Mountains and New 

England

Geologic Setting

The metamorphic history of the rocks in New England 

and eastern New York is complex because more than one 

metamorphic episode affected the region (figs. 11, 12; Drake 

and others, 1989; Osberg and others, 1989). These thermal 

events also affected the Grenville basement (fig. 6). The 

Taconic orogeny consisted of a complex series of orogenic 

episodes from Middle Ordovician to Early Silurian time (fig. 

11; Rodgers, 1971); earlier orogenic episodes may have been 

obscured or obliterated by deformational and metamorphic 

processes. Sutter and others (1985) suggested that the thermal 

peak for the dominant metamorphism in western New England 

occurred about 465 Ma, the generally accepted date for the 

Taconic orogeny. Radiometric and petrologic data indicate 

three metamorphic and structural domains of Taconic age 

(fig. 11): (1) a small area of relict high-pressure, low-temperature metamorphism in northern Vermont; (2) a broad area of 

normal Barrovian metamorphism in Vermont and eastern New 

York, with chlorite to garnet isograds representing a low thermal gradient; and (3) a narrow zone of Barrovian metamorphic 

rocks representing a steep geothermal gradient that trends 

northeastward from Dutchess County in New York, through 

Connecticut, to the Berkshire massif in western Massachusetts. Maximum metamorphic intensity coincides with maximum crustal thickening from imbricate thrusting (Berkshire 

massif) and recumbent folding (Manhattan prong) of remobilized North American continental crust.

The Devonian through Carboniferous Acadian orogeny 

in New England was accompanied by regional metamorphism (fig. 12) that occurred in two pulses (Osberg and 

others, 1989). Structural and textural relations date the earlier 

episode at about 394 Ma and the younger episode at about 

360 Ma. At higher structural levels, metamorphism is discontinuous and occurred over a period of 30 m.y. Contact 

metamorphism associated with plutonism ranges into the Carboniferous.

Maine

For years, rockhounds collected specimens of several 

minerals, including garnet, from the vicinity of old mines, 

U.S. Garnet Deposits
14 U.S. Industrial Garnet

quarries, and mine dumps, mostly in Oxford County (fig. 13; 

Fulkerson, 1974, 1976). Gem and specimen garnet were also 

reported from Androscoggin, Washington, and York Counties 

(Metcalf and Otte, 1961).

In 1977, Industrial Garnet Extractives, Inc., developed 

a garnet quarry at Wing Hill, north of Rangeley in Franklin 

County, western Maine (Barton and Doyle, 1981). The ore 

body trends east-west, is 1,000 m long, and is as much as 700 

-

-

-

-

-

-

-

0 10 20 30 40 50 KILOMETERS

Biotite (B)

Garnet (G)

Kyanite (K)

SillimaniteSillimaniteMedium-high-pressure

Ordovician plutons

Grenville basement

Chlorite zone

Chloritoid zone

Pumpellyite locality

muscovite (S)

K-feldspar (KS)

facies series

EXPLANATION

-

|

46o

45o

o 44

43 o

o 42

41o

-

74o 73o 72o 71o o 70

G

wm

em

nm

C

Ct

P

P

P

G

BM

GMM

hc

B K

G

K

K

G

B

B

B Ct

B

G

B

K

cm

hr HHM dc

CL

WD

hc

pr

G

B

at

cc MP S

s

s

s

KS

fg

-

-

G

K

C

Figure 11. Isograd map of Taconic metamorphism in New England (adapted from Drake and others, 1989a). 

Metamorphic grade of rocks increases from eastern New York to Cameron’s Line (CL) in Connecticut, 

through eastern margin of Grenville basement in western Massachusetts and southern Vermont, up to 

dotted line in northern Vermont. Isograds are based primarily on mineral assemblages in pelitic rocks; 

letter symbols are placed on higher-grade side of isograds. ad, Adamstown pluton, Maine; at, Attean 

pluton, Maine; BM, Berkshire massif, Mass.; bm, Belvidere Mountain, Vt.; cc, Cortland Complex, N.Y.; 

cm, Canaan Mountain, Conn.; dc, Dutchess County, N.Y.; em, Elsmore Mountain, Vt.; fg, Fordham Gneiss, 

N.Y.-N.J.-Conn.; GMM, Green Mountains massif, Vt.; hc, Highlandcroft pluton, Vt.; HHM, Hudson Highland 

massif, N.Y.-Conn.; hr, Hudson River, N.Y.; MP, Manhattan Prong, Conn.-N.Y.; nm, Northfield Mountain, Vt.; 

pr, Pliny Range, N.H.; WD, Waterbury Dome, Conn.; wm, Worcester Mountains, Vt.
15

m thick (Austin, 1993b). The garnet ranges in specific gravity from 3.6 to 4.3, and in hardness from 7 to 8 Mohs. Mining 

began in 1979 (White and Anderson, 1981) and continued 

until 1988. The ore is garnet granofels and garnet-bearing diorite associated with the contact zone of a gabbro pluton. The 

ore averaged about 60 weight percent almandite and 40 weight 

percent combined andesine, pyroxene, cordierite, and xenoliths. Garnet reserves were estimated at 1.8 million t. The rock 

had been exposed by glaciers, and so no overburden needed 

to be removed. The quarry produced garnet for abrasives, outdoor airblasting, filtration media, and nonskid aggregates. Raw 

crushed rock from the quarry was used for heavy aggregate 

and ornamental use. Some coarsely crushed grit was used for 

nonslip traction on snow and ice. Crushed garnet was transported to a mill in West Paris, in Oxford County, 120 km south 

of Rangeley (Prosser and others, 1983).

Figure 12. Isograd map of Acadian metamorphism in New England (adapted from Osberg and others, 1989).

Quebec

New York Vermont

New Hampshire

Maine

Quebec

Maine

New Brunswick

Maine

Ve mr ont

New Hampshire

New Hampshire Massachusetts

New York

Vermont Vermont

Massachusetts

Massachusetts

Connecticut

Connecticut

Rhode Island

New York

Connecticut

BOSTON

ALBANY. .

0 50 100 150 200 KILOMETERS

Granulite facies

Amphibolite facies—

 Sillimanite-orthoclase zone

Amphibolite facies—

 Sillimanite-muscovite zone

Amphibolite facies—

Kyanite-staurolite zone

Amphibolite facies—

 Andalusite-staurolite zone

Epidote-amphibolite facies—

Garnet zone

Greenschist facies—

Biotite and chlorite zone

Weakly metamorphosed

U.S. Garnet Deposits
16 U.S. Industrial Garnet

In 1983 and 1984, Maine was the second-largest garnetproducing State (Prosser and others, 1985, 1986). Although 

domestic garnet production was 24 percent higher in 1985 

than in 1984, Industrial Garnet Extractives increased its 

output by 61 percent during the same period (Prosser and 

others, 1987), possibly owing to an equipment upgrade in the 

previous year (Prosser and others, 1986). International Garnet 

Extractives ceased processing garnet at its West Paris plant 

in early 1988 (Harrison and others, 1991), when mining near 

Rangeley also ceased. In 1991, the Pittston Mineral Ventures 

Co. of Greenwich, Conn., announced plans to reactivate the 

dormant garnet quarry and construct an adjacent processing plant. Before they could proceed, however, the area of 

operations had to be rezoned by the town of Rangeley, and 

Pittston’s plans had to be approved by the State’s environmental authorities. In 1993, the Rangeley Minerals Resources 

Co., a subsidiary of the Pittston Mineral Ventures Co., surrendered its lease on the garnet quarry in Franklin County to the 

Rangeley Mining Co., Inc., the owners (U.S. Bureau of Mines 

staff, 1993–94a).

The Rangeley area is near the north end of the Bronson Hill-Boundary Mountain anticlinorium near the United 

States-Canadian border (BHBM, fig. 14; Cady, 1969). 

The anticlinorium can be traced southward along the New 

Hampshire-Vermont State line into western Massachusetts 

and northward into Quebec. Sedimentary and volcanic 

rocks composing this structure range in age from Cambrian 

through Devonian and are intruded by several calc-alkalic 

plutons of Ordovician and Devonian age and alkalic plutons of Jurassic and Cretaceous age. The volcanic rocks are 

interpreted to be parts of two volcanic-sedimentary-intrusive 

terranes, one of Middle Ordovician and the other of Upper 

Ordovician through Lower Silurian age (both affected by 

Taconic-age events). The Paleozoic terranes may have develFigure 13. County map of Maine, showing county boundaries and 

locations of counties (names in all caps) with garnet deposits or 

occurrences. Gem, gem-stone localities that may contain garnet. 

Dots, cities and towns; star, State capital.

Figure 14. Regional structures in northern New England (adapted 

from Moench and Aleinikoff, 2003). Blue, State and national boundaries: CAN, Canada; MA, Massachusetts; ME, Maine; NH, New Hampshire; VT, Vermont. Geologic features: BB, Bloody Bluff Fault; BHBM 

(red), Bronson Hill-Boundary Mountain anticlinorium; CMMT, Central 

Maine-Matapedia synclinorium; CVGT (green), Connecticut ValleyGaspe synclinorium (same as Townsend-Browning syncline of Cady, 

1969); DHG, Gneisses of Pelham Dome; FT, Frederick and Merrimack 

suture; LMA, Lobster Mountain anticlinorium; LSA, Lunkoos anticlinorium; MG, Massebesic Gneiss Complex; MWA, Munsungun-Winterville anticlinorium; NFS, Norumbega fault system; SFA, Shelbourne 

Falls arc; SMA, Stoke Mountain anticlinorium; SP, southeastern 

margin of Grenville basement; STH, Silurian tectonic hinge.

MWA

BHBM

BHBM

44o

|

|

68o

0 50 100 150 KILOMETERS
17

oped along subduction zones of opposing polarities (Drake 

and others, 1989; Moench and Aleinikoff, 2003).

New Hampshire

During the 1930s, New Hampshire was the leading 

garnet-producing State. Ladoo (1922) mentioned only one 

garnet locality in Merrimack County, near North Wilmot 

(fig.15); at the time of his report, the property was operated by 

the Wausau Abrasives Co. of Wausau, Wisc. The almandite, 

as large as 2 cm across, occurs in a matrix of biotite, quartz, 

and albite. The ore graded as much as 65 percent garnet but 

averaged much less. The garnets contained quartz and biotite 

inclusions, and so the ore had to be finely crushed to obtain 

sufficiently pure garnet sand. The Garnet Products Co. mined 

garnet from 1931 to 1934; no production was recorded for 

1935. In 1936, Garnet Products changed its name to the Davenport Garnet Co. and resumed mining until 1939. Another 

deposit near Danbury, also in Merrimack County, was operated by the Ford Motor Co. of Dearborn, Mich. From 1928 

to 1930, Ford shipped a few thousand tons of garnet from its 

Danbury operation to its plant in Dearborn for polishing plate 

glass (Conant, 1935). Ford’s garnet production was reported in 

the Minerals Yearbook 1931–32 (Hatmaker and Davis, 1933), 

although the garnet had been mined earlier. A garnet deposit 

near North Wilmot, also in Merrimack County, was mentioned 

in the Minerals Yearbook 1936 (Johnson and Davis, 1936); no 

production was recorded, and it is unclear whether this is the 

same deposit that was active in 1922 (see above). All of the 

mines are in western Merrimack County.

Conant (1935) reported that the garnet deposits in the 

Wilmot-Danbury area were in granitic gneiss and (or) migmatite and schist, containing as much as 80 volume percent 

garnet. The garnet content of the massive, higher-grade garnetiferous rocks ranged from 30 to 80 weight percent, averaging 

50 weight percent. Garnet masses were elongated parallel to 

the schistosity of the enclosing rocks. The garnet contained 

inclusions of magnetite, biotite, and quartz and had numerous 

fractures lined with chloritic alteration. The inclusions and 

alteration may have presented problems in using the garnet for 

abrasive applications. Its specific gravity, however, was about 

4.0, and its hardness 7.5 to 8 Mohs. The garnet was mostly 

almandite. The North Wilmot deposit was cut by vertical dikes 

of basalt (Triassic?) and pegmatite, neither of which appears 

to have altered the garnet; the rock also contains pyrrhotitetourmaline veinlets. The Danbury deposit is migmatitic and 

of lower grade than the Wilmot deposit. Other indications 

of garnet potential, such as many garnet-rich boulders and, 

possibly, an outcrop, were observed in West Andover, about 

5 km east of Wilmot in Merrimack County. Another garnet 

occurrence was reported near Bradford, about 24 km south of 

Wilmot, also in Merrimack County. The garnet deposits are in 

the Bronson Hill-Boundary Mountain anticlinorium (fig. 14; 

Cady, 1969; Moench and Aleinikoff, 2003), described previously.

Vermont

Green Mountain Mica Corp. in Gassetts in Windsor 

County (fig. 16) produced a small amount of garnet from 1939 

to 1941 for use as abrasives and in sawing marble. Since then, 

only rockhounds have collected specimens in the State (Kerr, 

1964). The mine is in the vicinity of the Chester dome (fig. 6) 

and close to the axial zone of the regional Townsend-Browning syncline (fig. 14; see Cady, 1969; same as the Connecticut 

Valley-Gaspe synclinorium of Moench and Aleinikoff, 2003), 

west of the Bronson Hill-Boundary Mountain anticlinorium. 

The core of the dome exposes complexly deformed and 

polymetamorphic upper Precambrian bedded shelf-facies 

rocks intruded by granitic plutons and pegmatite dikes. These 

rocks, which are considered to be outliers of the Grenville 

province (Rankin and others, 1989b), are overlain by Cambrian through Ordovician sedimentary rocks.

U.S. Garnet Deposits

Figure 15. County map of New Hampshire, showing 

county boundaries and location of Merrimack County, 

which has garnet deposits. Dots, cities and towns; 

star, State capital.

| N

-

--- .

.

.

.

.

.

.

.

MERRIMACK

Dover

Newmarket

Manchester

Newport

Keene

Laconia

Littleton

Berlin

.

. .

. . Nor Danbury th Wilmot

West Andover

Bradford

Concord

Wilmot

0 10 20 KILOMETERS
18 U.S. Industrial Garnet

Connecticut

Garnet deposits near Roxbury in Litchfield County, and in 

Roxbury Falls in New Haven County (fig. 17), were worked 

before the report by Ladoo (1922). The garnet, andradite, 

occurs in mica schist as dodecahedral crystals, as large as 5 cm 

across, that are easily separated from the schist. The deposit 

was worked mainly to furnish garnet for shoe finishing and 

mineral specimens; other uses included grinding wheels, saws, 

and sandpaper. Gem-quality garnets continued to be sought in 

the Roxbury area as of 1977 (Barton, 1981). Gem and mineral 

collectors have recovered garnet at various places in Fairfield, 

Hartford, and Litchfield Counties (Feitler, 1961). Garnets 

are still abundant in Bolton and Stafford Springs in Tolland 

County and in Portland in Middlesex County.

Violet-red almandite was designated the official Connecticut State gem stone in 1977.

Central and Southern Appalachian Mountains

Geologic Setting

The metamorphic evolution of the central and southern 

Appalachian Mountains, as in the northern part of the range, 

occurred over hundreds of millions of years, during which 

oceans opened and closed and accreted terranes docked 

against the Proterozoic core of North America. Granulitefacies metamorphism in the southern Appalachians occurred 

about 480 Ma (Rb/Sr age; Drake and others, 1989), or 

Taconic in age; many studies have reported both earlier and 

later dates. The isograds for the southern Appalachians shown 

in figure 18 were determined from the highest metamorphic 

grade in areas where isotopic data indicate Ordovician metamorphism. Temperatures at peak metamorphism ranged from 

540oC (staurolite-kyanite zone) to 775oC (granulite facies), 

and pressures from 3.8 to 9 kbars. Overall, Taconic metamorphism in the U.S. Appalachians was largely a mediumpressure-facies series, except for blueschist and eclogite in 

north-central Vermont (fig. 11) and a low-pressure-facies 

series in the central Appalachians (fig. 18).

The timing of Acadian metamorphism in the region is 

poorly constrained, ranging from Devonian through Mississippian. The isograds shown in figure 19 (from Osberg and 

others, 1989) were constructed during International Geological Caledonide Project 27. Acadian metamorphism is largely 

amphibolite facies superimposed on Ordovician and Precambrian metamorphic rocks. Garnets can be expected in rocks 

of appropriate composition for every metamorphic facies 

above greenschist. Acadian metamorphism, though not as 

intense as the Taconic, is widespread. Connections between 

the Acadian metamorphic belts in the central and southern 

Appalachians and similar belts in New England have not 

been reported.

In the southern Appalachians, Late Paleozoic and, 

possibly, Early Mesozoic dynamothermal metamorphism 

(Alleghenian through Pennsylvanian, Permian, and early 

Triassic?) is best known from the Raleigh and Kiokee belts 

Figure 16. County map of Vermont, showing 

county boundaries and location of Windsor 

County, which has garnet deposits. Dots, 

cities and towns; star, State capital.

| N 0 10 20 KILOMETERS

Figure 17. County map of Connecticut, showing county boundaries 

and locations of counties (names in all caps) with garnet deposits or 

occurrences. Dots, cities and towns; star, State capital.

-

0 25 50 KILOMETERS

. .

.

.

.

.

. Woodstock

WINDSOR

Chelsea

Rutland

Bennington

Middlebury

Montpelier

Burlington

| N
19

Pennsylvania

Before 1900, garnet was mined at several places in Chester and Delaware Counties (fig. 21). Judging from the size 

of the workings, one operation, about 2 km west of Chelsea 

in Delaware County, seems to have been the most important. 

There, almandite occurs within quartzose mica schist, locally 

composing 75 volume percent of the rock. The rock was heavily weathered at the surface (saprolite?) but became very hard 

at a depth of 7 m. A small amount of almandite was mined 

near Chester Heights, also in Delaware County. The ore was 

reached by tunnels and a shaft in heavily weathered gneiss 

(saprolite?; narrative from Ladoo, 1922). Rockhounds collected several minerals, including garnet, mostly in Chester 

(Cornog Quarry; Kerr, 1965) and Montgomery Counties. Mineral specimens, including garnet, were also collected in Lancaster, Lehigh, Luzerne, Monroe, and Northampton Counties 

(Yeloushan and others, 1963). The locations of collection sites 

and the varieties of garnet present were not reported. Garnet 

Figure 18. Isograd map of Taconic metamorphism in western North Carolina and adjoining States (adapted from Drake and others, 

1989). Sillimanite-grade metamorphism also occurs in the Inner Piedmont of South Carolina, but it is unclear whether Taconic metamorphism is preserved there. AA, Alto allochthon, Ga.; BR, Blue Ridge, Ga.-Tenn.; BZ, Brevard zone; cg, Chunky Gal mafic/ultramafic 

complex, Cherokee County, N.C.; cw, Cullowee, N.C.; dt, Ducktown, Tenn.; GMW, Grandfather Mountain window, N.C.; HF; Hayesville 

fault, Ga.-Tenn.; IP, Inner Piedmont; KMB, King Mountain belt; lc, Laurel Creek mafic/ultramafic complex, Ga.; MS, Murphy syncline, 

Ga.-N.C.; rm, Roan Mountain, N.C.-Tenn.; spd, Spruce Pine District, N.C.; SMA, Sauratown Mountains anticline, N.C.; SRA, Smith River 

allochthon, N.C.; VAR, Valley and Ridge province, Tenn.-N.C.; wsg, Winding Stair Gap, N.C.

U.S. Garnet Deposits

of the eastern Piedmont (fig. 20; Hatcher and others, 1989). 

The Raleigh belt lies along the northwestern margin of the 

Atlantic Coastal Plain from central North Carolina to southern Virginia; the Kiokee belt lies along the northwestern 

margin of the coastal plain from Columbia, S.C., to Augusta, 

Ga., and extends southwestward of Augusta into east-central 

Alabama. Alleghenian regional metamorphism in these two 

belts is superimposed on previously metamorphosed rocks 

that contain mineral assemblages ranging from greenschist 

(Taconic?) to granulite (Grenville) facies. The Alleghenian 

metamorphism itself ranged from greenschist to amphibolite facies. Maximum temperatures in the Raleigh belt were 

550–570oC, and ambient pressure was about 5 kbars. In the 

Kiokee belt, maximum temperature was 575±50oC in kyanite-staurolite schist at pressures of 7±1 kbars. Garnet deposits in these belts, if present, have not been described. On the 

basis of the metamorphic grades attained in these two belts, 

garnet deposits are possible (figs. 18, 19; see geologic details 

in Hatcher and others, 1989).

0 25 50 KILOMETERS
20 U.S. Industrial Garnet

crystals occur in cavities within metamorphosed Triassic conglomerate in York County (Stose and Glass, 1938). These garnets were formed in contact-metamorphic aureoles of diabase 

intrusions. The rounded cavities were produced by solution of 

limestone pebbles in the conglomerate. Evidently, these garnets date to a much later metamorphic event than the Acadian 

and other previously mentioned events.

Figure 19. Isograd map of Acadian metamorphism in the central and 

southern Appalachian Mountains (adapted from Osberg and others, 

1989).

Figure 21. County map of Pennsylvania, showing county boundaries and locations of counties (names in all caps) with garnet deposits or occurrences. Dots, cities and towns; star, State capital.

Figure 20. Southeastern United States, showing locations of the 

Raleigh and Kiokee metamorphic belts and their regional setting 

(adapted from Dallmeyer, 1989). ESB, eastern slate belt.

-

0 25 50 KILOMETERS

YORK

|

N

Pittsburg Altoona

Harrisburg)

Allentown

. Philadelphia

. Chelsea and

Chester Heights

|

_| |

LEHIGH NORTHAMPTON

Philadelphia

Harrisburg

Altoona

Pittsburg

MONROE

Allentown

LUZERNE

MONTGOMERY

LANCASTER CHESTER

YORK DELAWARE

Chelsea and

Chester Heights

0 25 50 KILOMETERS
21

Virginia

An attempt (in 1906?) was made to mine garnet from sericitic schist in a steep bluff on the northeast side of the Tyler 

River, about 6.5 km south of Arrington in Nelson County 

(fig. 22; Watson, 1907). No record of production is known. 

Euhedral spessartite crystals were collected from pegmatite 

dikes from which mica was mined near the Amelia courthouse 

in Amelia County and near Hewlett in Hanover County. The 

Morefield and Rutherford Mines in Amelia County produced 

gem-quality spessartite in the form of etched-crystal masses 

and fragments, ranging in size from 0.3 to 15 cm across, 

colored yellow-orange, red-orange, red, and brownish red 

(Ladoo, 1922; Metcalf and Calver, 1964). The mine still operates as a recreational collecting site (U.S. Geological Survey 

staff, 2005c). A shaft is driven into a quartz-feldspar pegmatite 

vein, and periodically material is blasted and dumped for collectors to sort. Minerals other than garnet include amazonite 

(blue-green microcline), amethyst, and beryl.

North Carolina

Garnet occurs in gneiss, schist, and igneous rocks in the 

central and southern Appalachian Mountains but is present in 

minable quantity and quality only in North Carolina (French 

and Eilertson, 1968; U.S. Geological Survey and U.S. Bureau 

of Mines, 1968). Counties named on the map of North Carolina (fig. 23) are associated in some way with garnet. Large 

deposits of almandite and rhodolite (a pink, rose, or purple to 

violet garnet intermediate in composition between almandite 

and pyrope) of gem and abrasive quality are known from 

Burke, Clay, Jackson, Macon, and Madison Counties. Garnet 

for abrasives was produced from some of these deposits from 

1900 to 1926, but no production figures were reported. The 

U.S. Geological Survey and U.S. Bureau of Mines (1968) 

reported garnet deposits in the following counties (dots, fig. 

23): one in southern Madison County, three in northern and 

western Jackson County, and two in eastern and southern Clay 

County. The largest deposits are in Clay and Jackson Counties, and the two largest deposits are at Penland Bald on Buck 

Creek and on Shooting Creek in Clay County. The deposits 

consist of almandite-rich hornblende gneiss containing garnet 

crystals, as large as 6 cm across. Rugged topography hinders 

development (Ladoo, 1922), or did so in 1922.

Three rhodolite garnet deposits occur on Sugarloaf and 

Doubletop Mountains, about 4 km south of Willets in Jackson County. Garnet crystals, as large as 3.5 cm across, occur 

in quartz-biotite gneiss, composing 25 to 50 volume percent 

of the rock. Mining began around 1900 and was intermittent 

until 1926. The Rhodolite Co. constructed a mill close to its 

quarry in the year before it closed. Reserves are estimated 

to be of high quality and easily accessible. The Savannah 

deposit at the head of Betty Creek and the Presley deposit 

near Speedwell in Jackson County operated intermittently for 

several years around 1900. Small garnet deposits southwest 

of Marshall near Little Pine Creek in Madison County were 

mined around 1900 or 1905. Garnet crystals, as large as 5 

cm across, were mined from a zone, as much as 3 m thick, 

in chlorite schist. From 1934 or 1935 until 1944, garnet was 

produced as a byproduct from the Celo Mines Co.’s kyanite 

mine near Burnsville in Yancey County (Espenschade and 

Figure 22. County map of Virginia, showing county boundaries and locations of counties (names in all caps) with garnet deposits or occurrences. Gem, gem-stone locality. Dots, cities and towns; star, State capital.

U.S. Garnet Deposits

HANOVER

.

Arrington

Richmond

0 50 Kilometers
22 U.S. Industrial Garnet

Potter, 1960; U.S. Geological Survey and U.S. Bureau of 

Mines, 1968). Production was suspended in 1941. The mine 

was reopened later that year by the Mas-Celo Mines Co. 

but was closed again in June 1942. The company was reorganized as the Yancey Cyanite [sic] Mine Co. and closed 

in January 1944, possibly owing to the declining grade 

of millfeed. Stuckey (1965), however, reported that Celo 

Mines produced byproduct garnet in 1944. Since then, only 

garnet for gems and (or) mineral specimens is known to 

have been collected in the State. Red gem-quality pyrope 

has been reported in mine waste from placer gold-mining 

operations in Alexander, Burke, and McDowell Counties. 

Pink rhodolite has been recovered from gravel in Cowee 

Creek near the town of Franklin and in Mason’s Branch 

near Iotla in Macon County, and occurs in place on Mason 

Mountain.

Overstreet and others (1968) summarized research on 

fluvial monazite deposits in the Southeastern United States 

that also contain ilmenite, rutile, magnetite, zircon, garnet, 

sillimanite, and kyanite (fig. 23). Early studies reported that 

the garnet from southeastern monazite placers was of good 

abrasive quality, but it was rejected or brought only low 

prices because of small grain size and roundness. From that 

time (1908?) to 1968, no effort was made to reinvestigate 

the placer garnet for industrial uses. Eventually, monazite 

placers between the Savannah and Catawba Rivers, N.C.-

S.C., were explored by drilling (Overstreet and others, 

1968). In addition to other heavy minerals, the placers 

yielded from a trace to 287 kg of garnet per cubic meter. 

Alluvial samples from the same area were sieved into four 

grain-size classes: gravel, sand, silt, and clay. Garnet content ranged from a trace to 38 kg/m3

 in the sand-size fraction and from 2 to 67 kg/m3

 in the gravel. Extraordinarily 

garnet rich samples (>67 to ≤287 kg/m3) were omitted from 

the average as anomalous and are not mentioned. The most 

common placer garnet composition was identified as a solid 

solution predominantly of spessartite and almandite.

Larsen (1993) reported high garnet concentrations 

in heavy-mineral suites in Mesozoic through Quaternary 

stream sediment on the Atlantic Coastal Plain of North Carolina (fig. 23; counties named in eastern North Carolina).

South Carolina

The garnetiferous region in South Carolina is a continuation of that in western North Carolina (fig. 24). Large garnet 

concentrations in Tertiary and Holocene monazite placers 

in the domain of metamorphic rocks of the Inner Piedmont 

occur in the Saluda, Pacolet, Enoree, and Tyger River drainages in northwestern South Carolina (fig. 24; Overstreet and 

others, 1968). Spessartite-almandite schist, a potential source 

of garnet placers, occurs in Cherokee and Spartanburg Counties. Relatively high garnet concentrations in heavy-mineral 

suites occur in Mesozoic through Quaternary stream sediment on and near the Atlantic Coastal Plain (fig. 24; Larsen, 

1993); these garnet occurrences are adjacent to counties in 

North Carolina where garnet also occurs in coastal-plain 

heavy-mineral suites (fig. 23). No record of garnet production is known for the State.

Figure 23. County map of North Carolina, showing county boundaries and locations of counties (names in all caps) with garnet deposits or

occurrences. Squares, cities and towns; star, State capital; dots, mines (inactive); Xs, garnet-collection localities (French, 1968), as of 1968. HM, 

in western North Carolina, streams with heavy-mineral suites that contain more than 5 weight percent garnet (Overstreet and others, 1968), 

and in southeastern North Carolina, garnet occurrences in heavy-mineral suites (Larsen, 1993) ; KS, kyanite and sillimanite production; P, large 

placer deposits that may include garnet (Gair and others, 1989).

ROBESON

COLUMBUS

CUMBERLAND

SAMPSON

Wilmington

Charlotte

GASTON

CATAWBA

ALEXRUTHERFORD

BURKE

LINCOLN

ANDER

CALDWELL

Greensboro

Winston-Salem

IREDELL

WILKES

POLK

YANCEY

JACKSON

CLAY

Raleigh

- —

BURLIN

JOHNSTON

HARNETT

— —

MACON

. x

..

.

HAYWOOD

..

. MADISON

CLEVELAND

ALLEGHENY ASHE

BUNCOMBE

x

x x

x

x

CHEROKEE

x .

x HENDERSON

x x x

x

MCDOWELL

x

MITCHELL

x

x

SWAIN

x

TRANSYL VANIA

x

.

KS

KS KS KS

KS KS

KS

KS

KS

KS

KS

KS

HM

HM HM

HM

HM

HM HM

HM

HM

HM

HM

HM

HM

HM

P

P

P

P P

HM

MECKLINKS BURG

KS

KS

KS

KS

P

P . ..

.

.

..

-

..

.

....

. .

.

..

.

..

.

..

.

-

|

N

_

-

-

0 50 100 KILOMETERS
23

Georgia

Almandite and pyrope in schist are widespread near 

Dahlonega, about 2 km south of Porter Springs in Lumpkin 

County (fig. 25; Richard, 1911). Much of the garnet is in saprolite and has weathering rinds. Fresh garnet is dark red and 

has a hardness of 5 to 6 Mohs, possibly a result of weathering. The larger garnet crystals ranged in weight from 28 g to 

several kilograms. Abrasive-quality garnet deposits may be 

present along with corundum, kyanite, and zircon. The U.S. 

Geological Survey and U.S. Bureau of Mines (1968) located 

one garnet deposit in northern Lumpkin County. Smith and 

others (1969) mapped metamorphic isograds in crystalline 

rocks of Georgia north of the Fall Line (the geographic line 

east of the Appalachian Mountains that marks the end of the 

Atlantic Coastal Plain and the beginning of the Piedmont, 

marked by numerous waterfalls and rapids). Most counties 

north of the Fall Line are underlain by amphibolite-facies 

rocks grading as high as sillimanite zone. The garnet isograd 

traverses the northwestern part of the State (fig. 25). Rocks 

between the garnet isograd and the Fall Line compose a 

complex of outliers of the Grenville province and Middle 

through Late Proterozoic metasedimentary, metavolcanic, 

and intrusive rocks (Rankin and others, 1989a). Most of this 

region theoretically had the pressure-temperature conditions 

for garnet formation, but garnet neomineralization would 

also depend on protolith composition. The garnet isograd 

passes westward into Alabama, indicating possible garnet 

occurrences, if not deposits, in east-central and northeastern 

Alabama.

The southeastern part of the Atlantic Coastal Plain in 

Georgia (fig. 25) contains heavy-mineral beach-ridge and 

channel-fill deposits of Pliocene or Pleistocene age (Pirkle 

and others, 1989, 1993). Although all the heavy minerals 

present were not reported, garnet commonly occurs in heavymineral suites on the coastal plain in North Carolina and 

South Carolina and is expected in similar environments in 

Georgia.

Figure 24. County map of South Carolina, showing county boundaries and locations of counties (names in all caps) with 

garnet occurrences. Dots, cities and towns; star, State capitals. Xs, garnet-collection localities (French, 1968), as of 1968. HM, 

garnet occurrences in heavy-mineral suites; KS, kyanite and sillimanite production.

U.S. Garnet Deposits

OCONEE

ANDERSON

PICKENS

GREENVILLE SPARTANBURG CHEROKEE

MARLBORO

DARLINGTON DILLON

MARION

FLORENCE
24 U.S. Industrial Garnet

Florida

Miller (1945) determined the abundances of heavy minerals of economic interest, including garnet, in 18 samples 

of dune and beach sand from Florida. Sampling sites were 

near Pensacola in Escambia County, at Clearwater Beach in 

Pinellas County, at Tampa Bay in Hillsborough County, at 

Fort Pierce in St. Lucie County, and at Vero Beach in Indian 

River County; on beaches along the coast of Flagler and St. 

Johns Counties; and in older dunes 16 km west of Jacksonville Beach in Duval County (fig. 26). Miller (1945) sampled 

heavy-mineral concentrate at a mining operation in older 

dunes 16 km west of Jacksonville Beach. Quaternary dune 

sand was also sampled 6 km south of Jacksonville Beach and 

150 m inland, 16 km south of Jacksonville Beach, and 6 km 

south of Atlantic Beach in Duval County. Heavy minerals 

are sparse in areas of Pleistocene sand inland from the coast 

and more abundant on modern beaches and in Holocene sand 

dunes along the coast. Some of the beach sand contains commercial deposits of heavy minerals.

Wave action on beaches concentrates heavy minerals in 

discontinuous lenses, from a few millimeters to 10 cm thick. 

Beach concentrations can change from one storm to the next, 

and heavy minerals may locally compose a large percentage of 

the sand. The Holocene dune deposits were initially concentrated on the beaches and later transported inland and sorted 

by the wind. Although the proportion of heavy minerals in the 

dunes is smaller than in the richer beach deposits, the large 

volume of the dunes may make them a potentially more attractive commercial source of heavy minerals than the beaches. 

Most production of rutile and ilmenite in 1945 was from the 

older dunes, but some beaches had also been productive. 

Heavy minerals still of interest in 2005 are ilmenite, rutile, and 

zircon, which are being mined in Baker, Bradford, Clay, and 

Duval Counties (fig. 26; U.S. Geological Survey and Spencer, 

2004), and concentrates of staurolite were also produced.

Figure 25. County map of Georgia, showing county boundaries and locations of counties 

(names in all caps) and isograds of Taconic metamorphism north of the Fall Line in northern 

Georgia (adapted from Drake and others, 1989). Dots, cities and towns; star, State capital.

0 25 50 KILOMETERS

| N

STAUROLITE

AREAS OF

LOW GRADE

METAMORPHISM

-

-

SILLIMANITE

SILLIMANITE

GARNET

SILLIMANITE

SILLIMANITE

Atlanta

. Brunswick

.Augusta

.

Macon

Columbus .

_

_

FANNIN RABUN

WALKER

CHATOOGA GORDON

CATOOSA

WHITFIEDMURRAY

FLOYD BARSTOW

PICKENS

POLK

LUMPKIN

HABERSHAM

GWINNETT

HART

ELBERT

HALL

MADISON

BANKS

FULTON

FAYETTE

HEARD

CARROLL

DOUGLAS

OGELTHORPE CLARKE

OCONEE

WALTON DE KALBROCKDALE

NEWTON MORGAN

LINCOLN

COLUMBIA

RICHMOND

HANCOCK PUTMAN

JONES MONROE

HARRIS CRAWFORD

COWETA

SPALDING SOLANO

PIKE

UPSON

HENRY

BUTTS

HARALSON

MERIWETHER

TALBERT

LAMAR

BIBB

MUSCOGEE TAYLOR

JASPER

BALDWIN

DADE
25

Heavy minerals in the beach and dune deposits include 

garnet along with corundum, enstatite, epidote, hornblende, 

ilmenite, kyanite, monazite, rutile, spinel, staurolite, tourmaline, and zircon (Miller, 1945). On the basis of index of 

refraction, the garnet was identified as belonging to the spessartite-almandite group. Garnet contents of the east-coast 

beach and dune samples ranged from a trace to 8 weight 

percent; the highest east-coast concentration was in a sample 

from the south bank of Matanzas Inlet in Flagler County that 

also contained 51 weight percent ilmenite. In comparison, the 

garnet content in dune sand at the ilmenite and rutile mine 

sampled by Miller (1945) in Duval County was 1 weight 

percent, along with 26 weight percent ilmenite and 5 weight 

percent rutile. On the west coast, garnet contents also varied 

widely and were highest at Tampa (5 weight percent) and 

Clearwater (18 weight percent); ilmenite and rutile contents 

were 22 to 26 weight percent at Tampa and 23 and 1 weight 

percent at Clearwater, respectively.

The record in the Minerals Yearbook notes that garnet was 

produced from black sand in Brevard and Indian River Counties 

from 1952 to 1957 (Reed and Calver, 1955, 1958; Thoenen and 

Calver, 1956; Chandler and Tucker, 1958d; Vallely and Calver, 

1958; Vallely and Vernon, 1959). These garnet sources were 

most likely beach and (or) dune deposits. Other abrasive minerals present in the dune and beach sand studied by Miller (1945) 

include kyanite, from a trace to 45 weight percent, and staurolite, from a trace to 47 weight percent. Both minerals are more 

abundant along the west coast, especially near Pensacola, where 

garnet is absent. In places, kyanite and staurolite could be mined 

as coproducts of heavy-mineral suites that include garnet.

Western United States

Much of the following narrative is derived from the Minerals Yearbook 1933–2004 (Kaufman and others, 1955; Baber 

Figure 26. County map of Florida, showing county boundaries and locations of counties (names in all caps) with 

occurrences of garnet or other heavy minerals. Dots, cities and towns; star, State capital. Ti, ilmenite and rutile; 

Zr, zircon production from heavy-mineral deposits.

U.S. Garnet Deposits
26 U.S. Industrial Garnet

and others, 1956, 1959a, b; Fulkerson and others, 1962; Gray 

and others, 1964; Knostman and Peterson, 1965; Carrillo and 

others, 1967; Collins and others, 1967; Bennett and Mitchell, 

1988; Gillerman, 2001).

Idaho

Placer Garnet Deposits of Northern Idaho

Emerald Creek Area

The garnet deposits at Emerald and Carpenter Creeks in 

Benewah County have accounted for as much as 10 percent of 

global garnet production, constituting the only continuously 

active garnet mine in the Western United States from 1940 to 

2005 (fig. 27). The garnet-bearing gravel is from 1 to 1.2 m 

thick and contains as much as 20 weight percent garnet. The 

gravel is sandwiched between underlying dark-blue-gray lakebeds and overlying barren gravel or loess, ≥2 m thick (fig. 28). 

Unconsolidated garnetiferous gravel consists of poorly sorted 

pebbles and cobbles containing abundant sand-size grains of 

garnet in, locally, a matrix of blue-gray mud (fig. 29). The 

upper part of the garnet-rich gravel is commonly oxidized. 

Some thin hematite-cemented beds (ferricrete) are extremely 

hard and provide clasts for cannibalized gravel. The bedrock 

sources of the garnet are schists, estimated at 1,200 m thick 

(see next subsection). Processing is simple: the gravel is first 

run through trammels to sort by size and is subsequently conFigure 27. County map of Idaho, showing county boundaries and 

locations of counties (names in all caps) with garnet deposits 

(circles). Dots, cities and towns; star, State capital.

Loess

Garnetiferous gravel

|

Figure 28. Recent cut through loess and garnetiferous gravel in the 

Emerald Creek area, Idaho. Inset, closeup of hematite-cemented 

gravel, showing evidence that garnet-bearing gravel was at the surface before burial by loess. Photograph courtesy of Michael Zientek, 

U.S. Geological Survey.

Barren gravel

Oxidized zone

Garnet placer

Figure 29. Recent cut through barren surface gravel to garnet placer 

with upper oxidized zone along Carpenter Creek, Idaho. Exposed 

thickness of unoxidized (purple) placer is about 1 m, although total 

thickness may be greater.

0 50 100 KILOMETERS

SHOSHONE

CLEARWATER

McCall

Cascade Gold ForkLittle Valley

Mountain Home

Challis

Idaho Falls

Pocatello

Twin Falls Burley

Soda 

Springs

Idaho City

Caldwell

Boise

Council

Orofino

Grangeville

Wallace St. Maries

Coeur d’Alene

Moscow

Lewiston

Fernwood BENEWAH

Emerald Creek

Carpenter Creek

Clarkia

IDAHO

ADAMS LEMHI VALLEY

CUSTER

ELMORE

OWYHEE

CASSIA

BOISE

BLAINE

ADA

Weiser

Salmon
U.S. Garnet Deposits 27

centrated in jigs and on shaking tables; the concentrate is then 

washed, dried, crushed, and screened.

Although garnet occurrences are relatively common in 

Idaho, the only active garnet mine is the Emerald Creek Mine 

between the towns of Fernwood and Clarkia in Benewah 

County (figs. 27, 30). Alluvial garnet placers were known 

from the Fernwood area in the 1880s, when gold prospectors 

found garnet clogging up their sluicing equipment. Garnet also 

occurs in parts of adjacent Clearwater, Latah, and Shoshone 

Counties and in the black sand placer deposits of central Idaho 

(discussed below). Commercial operations in northern Idaho 

did not begin until 1940. From 1944 to 1949, two companies 

worked garnet placers in two different creeks, Emerald Creek 

and adjacent Carpenter Creek to the north (fig. 30). From 

1950 to 1960, only one company, the Emerald Creek Mining 

Co., continued mining in Emerald Creek; however, from 1961 

Figure 30. Geologic map of the Emerald Creek area, Idaho. Crosses, peaks. 2G, 281 Gulch; GG, Garnet Gulch; NNG, No Name Gulch; PWG, Pee 

Wee Gulch.

Private permit

Campgrounds

Star garnet locality

Garnet isograd

Stream

Mined

Reserves

Alluvium

Wallace schist

Quartzite and amphibolite

Other metamorphic rocks

EXPLANATION

Meadow

Creek

Meadow

Creek

East Fork

Carpenter

Creek

Emerald

Emerald

Fork

Fork

West

East

Creek

Creek

Cat Spur

Creek

Purdue

River

St. Maries

Wood River

Hidden Gulch

Anthony Peak Clarkia

Emerald Creek Mining

Fernwood

Creek

Emerald Butte

Bechtel Butte

NNG

GG

2G

PWG
28 U.S. Industrial Garnet

Figure 31. Star garnet.

to 1980, the Idaho Garnet Abrasive Co. mined in Carpenter 

Creek. From 1964 to 1980, Idaho Garnet Abrasive was a division of the Sunshine Mining Co. From 1981 to 2005, the Emerald Creek Garnet Co. produced garnet from both Emerald and 

Carpenter Creeks; in 1991, the company became a division of 

World Garnet International, Ltd., subsequently renamed WGI 

Heavy Minerals, Inc. In 1997, proven reserves of garnet in the 

Emerald Creek area were 635,200 t, probable reserves 14,200 t, 

and indicated resources at least 78,462 t; a more recent (2002) 

estimate of proven reserves of garnet was lower (table 2). From 

December 1995 to March 1998, 58,017 t of dry garnet was 

produced from the Emerald Creek Mine (annual production, 

~25,225 t). Other garnet deposits occur along the East Fork 

of Emerald Creek; along Meadow Creek, about 6.4 km from 

garnetiferous mica schist; along with gold in the North Fork 

of the Potlatch River; and along Garnet, No Name, and Pee 

Wee Gulches and the Little East Fork, south of the present 

public garnet-panning area in 281 Gulch (fig. 27). Pee Wee 

Gulch was the former site of the public panning area. Garnet, 

No Name, and Pee Wee Gulches contain old pits dug to obtain 

gem-quality garnet.

Star garnet (fig. 31) occurs in association with industrial-grade almandite in 281, Garnet, No Name, and Pee Wee 

Gulches; other star garnet localities are on Wood Creek, which 

drains the south flank of Bechtel Butte; on Cat Spur Creek in 

Benewah County; in Purdue Creek in Latah County; and at a 

locality along the East Fork of the Potlatch River, about 2 km 

southeast of Bovill, also in Latah County (fig. 30). The only 

other area in the world reported to produce star garnet is in 

India.

Star garnet was designated the official Idaho State gem 

stone in 1967.

The Emerald Creek Garnet Co. has two leases on private 

and U.S. Government land that were due to expire in 2005 and 

2006, as well as two other leases in the St. Maries River area 

that are due to expire in 2009. In March 2004, the Section 404 

operating permit issued pursuant to the Clean Water Act by the 

U.S. Army Corps of Engineers was granted a 10-year extension, which included operations on 132 ha in the St. Maries 

River area; the permitted area includes 54 ha of wetlands adjacent to the company’s existing processing plant (WGI Heavy 

Minerals, Inc., 2005).

WGI Heavy Minerals, Inc., imports garnet mined from 

beach sand from its holdings in India to blend with its domestic 

product from northern Idaho (Emerald Creek Garnet Co., written commun., 2003). About 90 percent of Indian production is 

for markets in Asia and the Middle East. WGI’s main office and 

base of its international operations, which include Transworld 

Garnet Pvt. Ltd., of Tamil Nadu (URL http://transworldgarnet.

com/), southeastern India, and Kominex Mineral Mahlwerk 

GmbH of Ermsleben, Germany, is in Coeur d’Alene, Idaho 

(Willis, 2003). Branch offices are in Seattle, Wash.; Whittier, Calif.; Rotterdam, the Netherlands; Frankfurt, Germany; 

and Dubai, United Arab Emirates. WGI’s European operation 

mostly recycles and sells garnet for abrasive airblasting. In 

2001, WGI established a subsidiary, WesJet International Services GmbH, so that its garnet customers could obtain needed 

waterjet parts. In 2005, WGI acquired International Waterjet 

Parts (IWP), Inc., of Ephrata, Wash., which has a long record of 

pioneering and service in the waterjet industry, and controls the 

entire manufacturing process of their equipment and replacement parts (WGI Heavy Minerals, Inc., 2005).

The place of the Emerald Creek-Carpenter Creek garnet 

placers in the overall resource picture of WGI Heavy Minerals, Inc., (2002) is summarized in table 2. Clearly, northern 

Idaho garnet resources are small (5 percent of total) relative 

to the garnet resources blocked out in India. In addition, the 

Indian operations include other heavy minerals; especially 

ilmenite, that are not mined along with garnet in Idaho.

Staurolite (Fe2Al9O6[(Si,Al)O4]4(OH)2, specific gravity, 

3.74–3.83; hardness, 7.5 Mohs; Nesse, 2004) occurs in some 

of the pebbly gravel tailings along Emerald Creek, the West 

Fork of Emerald Creek, and Carpenter Creek, but no effort 

has been made to recover it, and it is unclear whether it can be 

produced profitably. At least one source of the staurolite seems 

to be a relatively small area in the central part of the Fernwood 

quadrangle. Field studies suggest that the detrital staurolite 

is mainly from a second generation of the mineral, most of 

which occurs in small grains; however, grains as large as 1 cm 

across are locally common in dredge tailings along Carpenter 

Creek, and as much as 3 cm long in metapelite exposed in 

nearby roadcuts.

Garnet Source

Garnet in the placer deposits in Emerald and Carpenter 

Creeks derives from weathering of metapelite (retains bedding; fig. 32) and schist (developed schistosity; bedding 

transposed or obliterated) believed to be the stratigraphic 

equivalent of shale of the Wallace Formation of the Belt 

Supergroup (Hietanen, 1963; Lewis and others, 2000). The 

garnetiferous rock was subjected to deeply penetrative weathering during the Tertiary that resulted in the formation of thick 
29

Figure 32. Metapelite with well-preserved bedding. Inset, hand specimen of bedded metapelite containing garnet porphyroblasts.

U.S. Garnet Deposits

saprolitic zones which are locally preserved beneath a varying 

thickness of overburden of Tertiary gravel and loess. Some of 

the garnet concentrations are within the saprolitic zones, but 

most are in the heavy-mineral fractions of gravel overlying 

and locally intercalated with Tertiary lakebeds in modern and, 

possibly, ancestral drainages (see below). The area has a history of sedimentation associated with Miocene Lake Clarkia 

(Rember, 1991) and, possibly, one or more other lakes created 

by damming of paleodrainages by Columbia River Basalt 

and (or) Tertiary fault movements. A program of trenching of 

alluvium in gulches and auger drilling along ridgetops was 

initiated by the U.S. Forest Service (USFS) in October 2002 

under the direction of Christopher Dail to determine where to 

relocate the public panning area, now in 281 Gulch (fig. 33), if 

the need to do so arises (lack of garnet or dangerously undercut creekbank). Although the complete results of that study are 

still pending, perched gravel and sand were observed along 

several ridgecrests, and garnet-poor as well as garnetiferous 

gravel was penetrated during trenching. The preponderance 

of very well rounded granite pebbles and cobbles and abundant kyanite, sillimanite, staurolite, and other resistant heavy 

minerals (corundum?) in some samples may reflect either a 

separate provenance or, possibly, more than one cycle of erosion-deposition of the gravel during which the garnet was 

destroyed.

A USFS lidar survey of a large tract of northern Idaho, 

including part of the Emerald Creek drainage, provides evidence of recycling of garnet from paleoplacers. The slope map 

for part of the survey area in the vicinity of 281 Gulch (fig. 33) 

is interpreted to show an elevated ancestral drainage parallel to a 

northeast-trending segment of the East Fork of Emerald Creek. 

The paleodrainage encompasses old garnet diggings in Garnet, 

Figure 33. Slope map of part of the East Fork of Emerald Creek, Idaho. 

Purple and dark-blue areas, low slopes along streams and ridgetops; 

orange and red areas, steep slopes along roadcuts and bordering 

incised channels of the East Fork and its tributaries. Courtesy of Christopher Dail, U.S. Forest Service. Red Xs, public panning areas.

0 300 600 METERS
30 U.S. Industrial Garnet

No Name, and Pee Wee Gulches and the two public panning 

sites along forks of 281 Gulch.

The evidence of multistage erosion-deposition suggests 

that some of the garnet in alluvial deposits of Emerald and 

Carpenter Creeks and of the St. Maries River in the ClarkiaFernwood area may not have come from nearby rocks but from 

metamorphosed rocks to the south and (or) east of Clarkia that 

underwent garnet-grade or higher-temperature metamorphism. 

Cyclic erosional processing of garnet may explain the occurrence of garnet along Meadow Creek, which is west of garnetiferous metapelite of the Wallace Formation. Recognition of peak 

metamorphic grade in potentially garnetiferous rocks southeast 

of Clarkia is obscured by intensive biotite-grade metamorphism 

that destroyed traces of garnet and higher-grade index minerals, 

as well as earlier structural elements.

Description of Garnet

Garnets in the Emerald Creek area (figs. 30, 33) range in 

color from pink to dark red, purple, and dark maroon and are 

as large as 2 cm across. Some dark-red to reddish-black opaque 

garnets have the pronounced multirayed asterism of star garnet 

(fig. 31). At least eight localities where star garnets have been 

obtained are in and near the Emerald Creek deposits (fig. 30). 

Inclusions responsible for asterism are composed of rutile 

(Johnston, 1983).

Garnets occur in metapelites as euhedral to subhedral porphyroblasts and anhedral grain fragments. Textures suggest that 

they coexisted with the metamorphic aluminosilicate minerals 

kyanite, staurolite, and sillimanite, indicating garnet formation 

and (or) stability in the amphibolite facies; metamorphism as 

high as sillimanite-muscovite zone is locally accompanied by 

little or no garnet. The garnets have a specific gravity of 4.0 to 

4.1 and a hardness of 7.5 to 8.0 Mohs (Emerald Creek Garnet 

Co., written commun., 2003). The garnets contain numerous 

solid inclusions of ilmenite, apatite, quartz, zircon, monazite, 

tourmaline, and fluid (fig. 34). Many garnets have highly fractured margins and an Fe oxide shell. Some garnets are so heavily weathered that they crumble under slight stress.

Garnets from 12 localities in the Emerald Creek area (fig. 

30) range in color from light pink to deep red and consist of 80 

weight percent almandite (West and others, 2005). Cores are 

relatively rich in Ca and Mn, and rims in Fe and Mg. Inclusions tend to be aligned in concentric growth zones in some 

garnets. The garnets are composed of 33 to 39 weight percent 

SiO2, 20 to 23 weight percent Al2O3, 0.5 to 2.5 weight percent 

MnO, 34 to 38 weight percent FeO, and 0.25 to 4.25 weight 

percent MgO. Except for CaO, these compositions are close 

to the composition of almandite in the placer deposits of the 

Emerald Creek area, according to the Emerald Creek Garnet 

Co. (fig. 30; see above). Garnets that persist in the gravel are 

rich in alumina (>22 weight percent Al2O3) and manganese 

(1.5–2.5 weight percent MnO); many are rimmed with secondary minerals, chiefly Fe oxide minerals (fig. 34), that show 

zoning of Al content and fill veins in the garnet. On the basis 

of the differences in composition of the garnets, some of the 

garnet in placers did not come from local schist (N. Foley, oral 

commun., 2006). A crystallization temperature of 500–600oC 

was estimated from two-mineral geothermometry, with the 

temperature increasing throughout garnet growth (Nicholson 

and others, 2003); the locations of the samples analyzed were 

not described.

Mineral relations in the Emerald Creek area (fig. 30) are 

complex because both prograde and retrograde reactions have 

occurred (fig. 35). Much of the heat and strain recorded in these 

rocks may be from emplacement of the Bitterroot lobe of the 

Idaho batholith (Barton and others, 1988), but one or more 

previous metamorphic events are suggested by widespread 

kyanite and sillimanite. Recently obtained Lu-Hf ages on garnet 

from the Emerald Creek area that range from about 1,065 to 

1,285 m.y. support a protracted deformational and metamorphic 

history for metapelites in that area (Jeffrey Vervoort, written 

commun., 2006). A Mesozoic(?) granitic intrusion is exposed 

along the West Fork of the St. Maries River, about 3 km south 

of the garnetiferous metapelite on Bechtel Butte (fig. 30; 

Hietanen, 1963). The northeast-trending granite dike, 4 km long 

and 0.6 km wide at its broadest part, may be responsible for the 

epidote-amphibolite metamorphism of nearby calc-silicate rocks 

included in the Wallace Formation. Pegmatite veins and (or) 

thin granitic dikes occur in metapelitic and calc-silicate rocks 

in the Emerald Creek area. Some of the metapelitic rocks may 

have undergone late greenschist-facies metamorphism, accompanied by complex deformation that included modification or 

obliteration of earlier fabric elements.

Garnet in Black Sand Deposits of Central Idaho

The following narrative is adapted from the monograph by 

Savage (1961). Information for the period 1951–66 is from the 

2

—1 mm

—

—

—

—

Fe oxide shell Fe-oxide shell

Core

Fe-oxide shell

Garnet

Inclusions

Figure 34. Inclusions in garnet from the Emerald Creek area, Idaho. 

Photomicrograph courtesy of Nicolle West, U.S. Geological Survey.
31

Minerals Yearbook (Baber and others, 1956, 1959a, b; Fulkerson and others, 1962, 1963; Gray and others, 1964; Knostman 

and Petersen, 1965; Carrillo and others, 1967; Collins and 

others, 1967).

From 1951 to 1966, one to three companies produced 

garnet as a byproduct of black sands in Valley County, central 

Idaho (fig. 27). Target minerals were ilmenite, monazite, and 

rare-earth-rich heavy minerals; garnet was also concentrated 

and sold. Gem-quality garnet occurs close to garnetiferous black 

sand deposits in the area of the North Fork and Little North 

Fork of the Clearwater River in Clearwater County.

The discovery of gold in sand and gravel deposits near 

Pierce in Clearwater County (fig. 27) started a widespread 

search for other placer and lode minerals. Since then, nearly 

all of central Idaho’s black sands and many streams have been 

worked for gold. Overlooked in the past were dark heavy 

minerals that may potentially constitute resources of niobium, 

yttrium, zirconium, hafnium, uranium, thorium, titanium, and 

rare-earth elements. More than 50 minerals are present in the 

heavy-mineral suites. The black sand placers were formed as a 

result of erosion, sorting, and deposition of heavy minerals from 

disintegrating rocks of the Idaho batholith and associated metaSillimanite

|

Muscovite after andalusite

|

Coarse muscovite corona

_

Kyanite

_

|

|

1cm

|

1 cm-

-

-

-

A C

B

D

E

|

1 cm-

-

Muscovite after staurolite

Muscovite after staurolite

Unaltered staurolite

|

|

-

_

_

1 cm

Figure 35. Metamorphic minerals in rocks from the Emerald Creek area, Idaho. A, Sillimanite in garnet-mica schist. B, Muscovite pseudomorph 

after andalusite; blue-gray core consists of fine-grained chaotic muscovite, in contrast to coarser silvery-gray muscovite along margins. C, 

Large kyanite porphyroblasts in metapelite, partly altered to sillimanite; small purple dots are garnet. Photograph courtesy of Michael Zientek, 

U.S. Geological Survey. D, Blue-gray muscovite pseudomorphs (such as described in fig. 35B) after twinned early staurolite. E, Two generations 

of staurolite: first-generation porphyroblasts are large and altered to muscovite; second-generation porphyroblasts are small and unaltered.

U.S. Garnet Deposits
32 U.S. Industrial Garnet

morphic rocks and the accumulation of heavy minerals during 

one or more cycles of uplift, erosion, and deposition. Garnet is 

virtually ubiquitous in heavy-mineral concentrates. Although no 

areas containing abundant garnet have been found in association 

with the black sand deposits, garnet sand is one of the mineral 

concentrates that have been produced from the placers and marketed.

Mining and processing of the black sands of central Idaho 

for garnet is recorded in the Minerals Yearbook as far back 

as 1946–48, when Baumhoff-Marshall, Inc., and the IdahoCanadian Dredging Co., working jointly, saved part of their 

jig-concentrated black sands while dredging for gold near Centerville in Boise County (fig. 27; Savage, 1961). These black 

sands, stockpiled mainly for monazite, zircon, ilmenite, and 

other minerals containing rare earths, uranium, and thorium, 

were eventually reprocessed for garnet. In 1949, Rare Earths, 

Inc., planned to produce garnet as a byproduct of its monazite 

operations (Metcalf, 1951); no further mention of this company or operation was found. In 1952, three companies were 

dredging near the town of Cascade in Valley County: Baumhoff-Marshall, Inc., the Idaho-Canadian Dredging Co., and 

Warren Dredging (Kaufman and others, 1955). In 1953, the 

Idaho Titanium and Mining Co. recovered abrasive garnet at its 

plant in Idaho County. The concentrate was originally dredged 

by the K&D Mining Co. at Ruby Meadows near Burgdorf in 

Idaho County (Baber and others, 1956). In 1957, BaumhoffMarshall produced concentrates of garnet, monazite, zircon, and 

ilmenite at its plant in Ada County. From 1951 to mid-1955, the 

company reprocessed stockpiles that were obtained from black 

sand deposits near Cascade in Valley County; all fractions were 

shipped out of State. Porter Brothers Corp. produced heavy 

minerals containing niobium and tantalum (columbite [niobite], 

tantalite); and rare earths, thorium, and uranium (euxenite, monazite) from sand dredged from Bear Valley in Valley County. 

The rough concentrate was shipped to Lowman in Boise County 

for final separation (Baber and others, 1959a). In 1958–59, 

Porter Brothers dredged heavy minerals from Bear Valley, and 

the rough concentrate was shipped to its plant at Lowman for 

final separation. Concentrates of columbite, euxenite, monazite, magnetite, ilmenite, and garnet, and zircon-quartz sand 

were produced. Columbite and euxenite were shipped out of 

State, and the rest of the sand concentrates were stockpiled at 

Lowman. The last shipment of euxenite concentrate was sent 

in 1959 to fulfill a government contract (476 t containing 90 

weight percent Ni-Ta pentoxides; Kiilsgaard and Hall, 1995), 

and that part of the operation was shut down. In 1959, J.R. Simplot bought the Baumhoff-Marshall processing plant and continued to reprocess the stockpiles of rough concentrate that had 

been mined from Valley County. Over time, Porter Brothers’ 

dredging decreased, crude concentrates were stockpiled, and 

heavy-mineral concentrates, including garnet, were produced 

from the stockpiles. The latest garnet production was in 1966, 

when a small shipment was sent by Porter Brothers from its 

stockpile at Lowman.

A few black sand deposits were examined by the former 

U.S. Bureau of Mines. The black sand deposits at Gold Fork 

in western Valley County, which were worked for gold, are no 

longer active. These deposits, which are near the margins of the 

Baker and Challis 1o×2o quadrangles (Fisher and Johnson, 1995, 

pl. 23), are included in an area of high potential for radioactive 

black sand placers. Ilmenite and other black sand minerals that 

occur in alluvium along the Gold Fork River on the east side of 

Long Valley, 18 km north of Cascade, were derived from schist, 

gneiss, amphibolite, and granitic rocks of the Idaho batholith. 

Storch (1958) studied the deposits along a segment of the river, 

beginning at the junction of the Gold Fork and Payette Rivers, 

as part of the 1951 Atomic Energy Commission’s Western 

Radioactive Minerals Program, and later to determine how 

much of the black sand was unminable owing to inundation by 

highstands of water in the Cascade Reservoir. The deposits are 

in a segment of the Gold Fork River, about 10 km long by 300 

to 1,200 m wide. A total of 31 holes, ranging in depth from 17 to 

43 m, were drilled into the deposit, and core was recovered. The 

range of heavy-mineral content of unprocessed samples was not 

reported, nor was the composition of the garnet. The garnet content of composited black sand fractions from four holes drilled 

in 1956 ranged from 15 to 27.4 weight percent, second only to 

the ilmenite content (40–50 weight percent).

The Little Valley deposit, 30 km north of Cascade near 

the junction of Little Valley Creek (as named in Schmidt and 

Mackin, 1970; the North Fork of the Gold Fork River in Storch 

and Holt, 1963) and Flat Creek, was mined for gold. The alluvial gravel underlies an area of 890 ha to an average depth of 9 

m. The deposit is underlain by fine-grained lacustrine sedimentary materials with a low black sand content. The garnet content 

of the gravel was not reported (Storch and Holt, 1963).

Montana

Overview

Between 1996 and 2005, garnet was sporadically produced from two mines in Madison County, southwestern 

Montana (figs. 36, 37): the Ruby Garnet Mine (Cominco 

Ltd./Green Diamond Abrasives, the Montana-Oregon Investment Group, LLC, and Ruby Valley Garnet, LLC) at Alder, 

about 100 km south of Butte; and the Sweetwater Garnet 

Mine (Absolut Resources Corp., Cominco Ltd., and Stansbury Holdings Corp.), about 16 km east of Dillon (figs. 36, 

37). At the Ruby Garnet Mine, garnet was recovered from 

the large gold dredge tailings immediately east of Alder. 

Other placer tailings are present for several kilometers along 

Alder Gulch east of Alder and south of Virginia City, but 

until the mid-1990s, no efforts to recover the heavy minerals, 

other than gold, that might be present there were reported. 

The Ruby Garnet Mine was initially constructed and operated by Green Diamond Abrasives, a subsidiary of Cominco 

Ltd. Later, the mine was sold to the Montana-Oregon Investment Group, LLC, which operated it for a few years and then 

sold it to Ruby Valley Garnet, LLC, in 2004. Ruby Valley 

Garnet abandoned the dredge tailings, began mining much 

higher grade Tertiary and (or) Quaternary alluvial deposits, 
33

Figure 36. County map of Montana, showing county boundaries and locations of counties (names in all caps) with 

garnet occurrences. Talc, talc occurrences. Dots, cities and towns; star, State capital.

10

287 287

287

Figure 37. Part of Butte, Mont., area, showing locations of 

landmarks, including the Ruby Garnet Mine plant, Red Wash, 

the Sweetwater Garnet Mine, the Section 36 garnet deposit, 

and other sites mentioned in text. BNF, Beaverhead National 

Forest; DLNF, Deer Lodge National Forest.

and processed garnet sand in the plant constructed by Green 

Diamond. 

Ruby Garnet Mine

Part of the following narrative is adapted from the map 

by Van Gosen and others (1998). Mining in the Virginia City 

area of Madison County began in 1863 with the discovery 

of gold in Alder Gulch (Tansley and others, 1933), a tributary of the Ruby River (fig. 38). Gold-quartz vein deposits 

were discovered shortly afterward, and by 1870 several lode 

mines were in operation. The present tailings were created by 

a succession of gold dredges that began operations in 1889 

near the town of Ruby (near Alder) and in 1896 expanded 

into Alder Gulch. The gulch, which extends for 21 km from 

its headwaters south of Virginia City to the Ruby River, was 

the largest gold placer deposit in Montana. About 90 million 

t of alluvium were mined from 1899 to 1922 by the Conrey 

Placer Mining Co. (Santini and Barker, 2003). According 

to Dingman (1932), placer mining was ongoing in 1932. 

Total production of placer gold from Alder Gulch was more 

than 2 million troy oz. Stacked tailings were produced by 

the dredges that separated gravel from auriferous sand and 

placed the gravel on previously processed sand. Most of the 

garnet occurs in the sand.

In the 1990s, attention switched to the garnet that 

occurs in the voluminous (~38,400 m3) dredge tailings 

in Alder Gulch, especially in sec. 9, T. 6 S., R. 4 W., just 

U.S. Garnet Deposits

MADISON

BEAVERHEAD

Virginia 

City

Alder

Dillon

Butte

Helena

0 50 100 Kilometers

N

Talc Talc

Talc

Kallspell

Great Falls

Billings
34 U.S. Industrial Garnet

east of the town of Alder and south of the town of Ruby. 

Cominco Ltd. bought the tailings in 1989. From 1992 to 

1994, Cominco Ltd.’s Green Diamond Abrasives subsidiary 

sampled the tailings, including drilling 17 reverse-circulation holes in the tailings, experimented with beneficiation, 

tested pilot-plant operations, and conducted market-feasibility studies. On the basis of this work, proven reserves 

were estimated at about 29.5 million t containing 4.5 weight 

percent garnet. Construction of the plant began in 1994, and 

production started in 1996.

The garnet from tailings at the Ruby Garnet Mine consists of violet-red and reddish-brown almandite-pyrope that 

is chemically inert, has a specific gravity of 3.8 to 4.2 and a 

hardness of 7.5 to 8 Mohs, is angular to subangular in granularity, is reusable, and is nonhygroscopic (Santini and Barker, 

2003). Most of the garnet sales were for waterjet cutting at 

a list price of $240/t free on board at the mine but the garnet 

is also suitable for abrasive airblasting. Green Diamond produced garnet from 1996 to 1999; by 1999, the property had 

been for sale for some time.

U.S. Geological Survey accounts for 1999 and 2000 

conflict; either the property was sold to the Montana-Oregon 

Investment Group, LLC, in 1999 (U.S. Geological Survey 

staff, 2001), or Green Diamond Abrasives took an option 

on the Ruby Garnet Mine in 2000 (U.S. Geological Survey 

staff, 2002a). Inasmuch as Green Diamond Abrasives (see 

above) was a subsidiary of Cominco Ltd. that operated the 

Ruby Garnet Mine near Alder as of July 1996 (Green Diamond Abrasives, written commun., 1998), the first version 

of events is more likely. Santini and Barker (2003)’s version 

is that the mine was sold in 2000 to the Montana-Oregon 

Investment Group. The company produced garnet for nearly 

3 years and stopped production in 2002. At that time, two 

potential buyers had been identified; one wanted to operate the mine, and the other wanted to salvage the equipment 

(Harben, 2002). As of spring 2003, the mill was to be salvaged (R. Berg, written commun., 2003), although a skeleton 

crew was still in maintenance mode at the mine in September 

2003. At that time, about 5 percent of the extensive dredge 

tailings in sec. 9, just east of Alder, were closed to mining 

because they will be the site of a sewage-treatment plant for the 

town. Another small part of the western margin is being used 

as a local dump. A more substantial part of the western tailings 

has been processed for garnet.

Figure 38. Alder, Mont., area, showing locations of garnet-rich rocks and garnet placers (geology adapted from Vitaliano 

and others, 1979, and Wier, 1882, supplemented with 2005 field observations). Red lines, approximate areas containing 

garnet and (or) garnet potential; thick black line, fault; red Xs, garnet-rich outcrops; AG, alluvial garnet deposit; ALG, combined alluvial and lode garnet deposits; LG, lode garnet deposit; LG?, potential lode garnet deposit. Locations of ultramafic 

blocks south of Alder Gulch from Wier (1982).

Mafic metamorphic rocks

Ultramafic block

Ultramafic

Ultramafic block

Ultramafic block

Red Wash area

LG

LG?

LG

LG

LG?

LG?

LG?

ALG

X

X X

Granite

Creek

block
35

Figure 39. Biotite schist containing garnet-rich nodules and lenses 

(G) in the Alder Gulch area, Mont. (figs. 37, 38).

Figure 40. Migmatite in the Alder Gulch area, Mont. (figs. 37, 38). 

Fragments of garnetiferous amphibolite are separated by garnet-rich 

pegmatite veins.

In 2004, the mine was sold to Ruby Valley Garnet, LLC 

(Hart Baitis, proprietor), which began mining garnet from alluvial deposits from a drainage about 4 km southeast of Alder 

informally named Red Wash (fig. 38). The garnet was processed 

at the existing Ruby Garnet Mine plant and sold for abrasive airblasting and waterjet cutting.

Bedrock sources of the garnet are Archean rocks, principally 

amphibolite, biotite schist (fig. 39), migmatite (fig. 40), and some 

contiguous pegmatite and granite that intrude the Indian Creek 

Metamorphic Suite (Vitaliano and others, 1979) in the southern 

Tobacco Root Mountains (north of Alder Gulch; see Brady and 

others, 2004, for details of the geology) and similar rock in the 

northern Greenhorn Range (south of Alder Gulch; Weir, 1982). 

At least one period of granitic emplacement that postdates the 

migmatite destroyed garnet and mafic minerals in its aureole by 

altering them to chlorite and talc and by potassic metasomatism. 

Garnet placer and lode deposits are commonly associated with 

such rocks as mafic and ultramafic metamorphic rocks (black 

garnet-hornblende and “blackwall” of Vitaliano and others, 

1979). Much of Alder Gulch is flanked by garnetiferous rock 

(figs. 38–40), and so a large fraction of the garnet in the dredge 

tailings is not far from its bedrock source.

At Red Wash (figs. 38, 41), focus is on the younger channels 

in the Tertiary and (or) Quaternary sand and gravel. The apparent 

garnet source is the 100-m-thick section of exceptionally garnetiferous rocks in the N1⁄2 sec. 30, T. 6 S., R. 3 W. (fig. 38), on the 

north flank of upper Red Wash. The lode deposit contains much 

garnetiferous amphibolite, garnetiferous granitic dikes, and thin 

layers of garnetiferous biotite schist with sillimanite. Garnet porphyroblasts larger than 4 cm across are common.

Sweetwater Garnet Mine

The Sweetwater garnet deposit is on 753 ha of private land 

in secs. 16, 17, 20, and 21, T. 8 S., R. 6 W., at the northwest end 

U.S. Garnet Deposits

G

G

of the Sweetwater Basin in Madison County, about 16 km east 

of Dillon and 35 km southwest of the Ruby Garnet Mine (figs. 

37, 42). Absolut Resources Corp. (URL http://absolutresources.

com/; a recent visit to their Web site did not reveal any existing 

garnet operations), the earliest owner of the Sweetwater Garnet 

Mine, began operations in 1996 with plans to market its product as airblast abrasives under the trade name Red Dog Garnet. 

Production facilities, equipment, and an open pit were located 

in the N1⁄2SW1⁄4 sec. 17. The deposit was estimated to contain 8 

weight percent almandite in alluvial deposits. The garnet source 

was believed to be the surrounding quartzofeldspathic gneiss 

(Ruppel and others, 1993); however, the quartzofeldspathic 

gneiss observed in that area generally contains little garnet. 

Soon after making plans for mining garnet, Absolut sold the 

mine to Cominco Ltd., which put its operations at the Sweetwater Garnet Mine up for sale in 1998 (fig. 42; U.S. Geological 

Survey staff, 2000) and ceased operations in August of that year. 

The mine was acquired by Stansbury Holdings Corp. and was 

inactive as of fall 2003. In 2004, the mine was turned back to 

the Helles family that owns the land, the production equipment 

was removed, and the surface was reclaimed.

The mine area (fig. 42) was mapped by James (1990) and 

is included in his broadly defined quartzofeldspathic gneiss 
36 U.S. Industrial Garnet

A

B

C

D

Figure 41. Red Wash deposit, Mont. A, Trench wall at right angle to trend of Red Wash. Reddish brown 

garnetiferous gravel (right) fills cut in pale-gray older alluvial-fan deposits (left). B, Undisturbed high-grade 

garnetiferous sand and gravel in upper Red Wash. C, Garnet amphibolite exposure near Red Wash. D, Ridge on 

north margin of Red Wash exposes a 100-m-thick section of exceptionally garnet rich rocks (brown); source of 

garnets in Red Wash.
37

Figure 42. Sweetwater Creek area, Mont., showing locations of the 

Sweetwater Garnet Mine and the Section 36 garnet deposit. Red 

ovals enclose areas rich in garnet.

Figure 43. Pit wall at the Sweetwater Garnet Mine, Mont. (figs. 37, 42).

U.S. Garnet Deposits

(unit WVqg). Study of the deposit in 2003 by the first author 

indicated that the principal garnet-bearing zone at and near the 

mine is saprolitic mica schist, containing as much as 20 volume 

percent garnet, under an overburden of 0 to 4 m of barren surface gravel and sand (fig. 43); the saprolite may have been misinterpreted as Tertiary sand and gravel. Saprolitic mica schist 

and surficial lag deposits containing garnet (fig. 44) are widespread south of the mine. Garnet is also abundant in nearby 

biotite schist. Pegmatite and granite nearby are barren.

Evaluation of the Ruby Garnet and Sweetwater Garnet 

Mines

Garnet in the dredge tailings near Alder and in saprolite 

at the Sweetwater Garnet Mine do not clearly meet the criteria 

for an economic deposit, using 20 weight percent as the lower 

cutoff of the grade and the apparent sizes of the resources (see 

subsection above entitled ”Evaluation of Garnet Deposits”). 

The dredge tailings at Alder surpass the minimum tonnage 

requirements, but the garnet grade (4.5 weight percent) is too 

low. The grade of the garnetiferous saprolite at the Sweetwater 

Garnet Mine may be as much as 20 weight percent or even 

higher, and garnetiferous saprolite may underlie the low ridges 

south of the mine to an unknown depth, but garnet resources 

in the saprolite have not been estimated.

Section 36 Deposit

Ruby Valley Garnet, LLC, has claims covering a lode 

and alluvial garnet deposit informally known as Section 36 

(fig. 42) northeast of Elk Gulch on the Beaverhead-Madison 

County boundary. The claim area is adjacent to part of the Elk 

Creek vermiculite deposit of Berg (1995; map scale, 1:6,000; 

formerly the Dillon nickel prospect of Sinkler, 1942). The garnetiferous rocks occur in a zone about 2 km long by 0.05 km 

wide, trending east-northeast, in sec. 36, T. 8 S., R. 7 W.; in 

the SE1⁄4 sec. 35, same township; and in the NE1⁄4 sec. 2, T. 9 

S., R. 7 W. Lode ore consists chiefly of garnet-hornblende rock 

(figs. 45A, 45B). On the north and east, the ore body is partly 

enclosed in amphibolite, granitic gneiss, and biotite gneiss that 

contain small amounts of garnet; biotite gneiss is also present along part of the southwest end of the garnet amphibolite. 

Ultramafic rocks, largely harzburgite, and ultramafic metamorphic rocks (figs. 45C, 45D) nearby appear to compose a 

Figure 44. Garnet-rich saprolite south of the Sweetwater Garnet 

Mine, Mont. (figs. 37, 42). Garnet is further concentrated to 100 weight 

percent in small sand bars in ditch (lower right).
38 U.S. Industrial Garnet

slab that overlies part of the garnet amphibolite on the east 

and south and truncates the amphibolite on the west (Berg, 

1995). Desmarais (1976, 1981) described the ultramafic rocks 

as consisting of hypersthene megacrysts, amphiboles (actinolite/tremolite, anthophyllite/cummingtonite), spinel, and olivine. Most of the ultramafic rocks are metamorphosed to black 

hornblendite (no garnet); some of the hornblende forms pseudomorphs after orthopyroxene, the boundaries of which are 

etched on weathered surfaces, so that the coarse grains, crude 

layering, and folds in the harzburgite protolith can be identified despite the metamorphism. The garnet ore zone appears 

to be truncated on the west by ultramafic metamorphic rocks 

devoid of garnet. In 2003, Stansbury Holdings Corp. produced 

some garnet from a small (2,500-m2 area) part of the ore zone, 

which has been reclaimed; its primary interest was in nearby 

vermiculite deposits (Willett and Potter, 2004). Garnet-rich 

colluvial and alluvial(?) deposits extend an unknown distance 

to lower elevations southeast of the garnet amphibolite.

Other Garnet Occurrences

The garnetiferous zones along Alder Gulch, in Red Wash, 

in the northwestern part of the Sweetwater Basin, and in Section 36 are four of several garnet-rich bedrock sources in the 

area. Substantial amounts of garnetiferous rock were discovered in the following localities (fig. 37): (1) at an unnamed 

pass 6 km east of Virginia City on Montana Highway 287 in 

the headwaters of Eightmile Creek; (2) in granite along the 

east flank of Alder Gulch, a few kilometers south of Virginia 

City; (3) in rocks on both sides of the Ruby Dam, about 10 km 

south of Alder, including along Hinch Creek (southwest corner, 

fig. 38); and (4) in the headwaters of the North Fork of Stone 

Creek, about 1 km east of the Treasure Mine (talc) in the Ruby 

Mountains. Stream-gravel and alluvial-fan deposits in the headwaters of Eightmile Creek and the Ruby River may contain 

large amounts of garnet derived from the highly garnetiferous 

bedrock, but no placer deposits from those areas have been 

described. Hinch Creek has a local reputation for containing 

garnets, and rocks along the north side of the creek, including 

such garnet-hornblende rock as in the Section 36 garnet deposit 

(figs. 42, 45A), are rich in garnet. Quartzofeldspathic gneiss 

there also contains substantial amounts of garnet. Granite 

Creek in the southern Tobacco Root Mountains (fig. 38) was 

investigated for garnet placers, and rockhounds have recovered 

garnets from gravel in Barton Gulch in the Greenhorn Range, 

11 km south of Alder (Berg, 1990).

Garnet Sources in the Southern Tobacco Root Mountains

Other garnet resources may be present in the southern 

Tobacco Root Mountains (figs. 37, 38). The geologic map of 

the area (Vitaliano and others, 1979) shows the distribution 

of garnetiferous rocks, such as amphibolite and garnet gneiss 

between Alder Gulch and the Tobacco Root batholith about 

20 km to the north. On the basis of their geochemistry, the 

protolith of the mafic metamorphic rocks (part of the Indian 

Creek and Pony-Middle Mountain Metamorphic Suites) was 

largely tholeiitic basalt (Mogk and others, 2004). These rocks 

(fig. 38; mountains north of Alder Gulch) may have supplied 

one or more alluvial garnet deposits in the southern Tobacco 

Root Mountains, including the suggested deposits in the headwaters of Eightmile Creek and Granite Creek (see above). The 

Spuhler Peak Metamorphic Suite, 20 km north of Alder Gulch, 

and especially the orthoamphibole-garnet gneiss pictured by 

Burger and others (2004, fig. 2) and Cheney and others (2004, 

fig. 5), may be a source of placer garnet. On the basis of their 

geochemistry, the protolith of these rocks is interpreted to be 

mostly mafic volcanic rocks deposited in a marine environment 

(Burger and others, 2004). The 12-km-long exposure of the 

A

B

C

D

Figure 45. Rocks associated with the Section 36 garnet deposit, Mont. 

(figs. 37, 42). A, Garnet-hornblende rock, principal garnet source; red, 

garnet; black, hornblende. B, Large pink garnet in garnet-amphibolite. 

C, Coarse-grained harzburgite on southeastern flank of lode garnet 

deposit. Crude layering is approximately horizontal. D, Hand specimen 

of harzburgite; brown, enstatite; green, olivine.
U.S. Garnet Deposits 39

Spuhler Peak Metamorphic Suite suggests a potential for other 

alluvial garnet deposits in drainages emerging from this part of 

the southwestern Tobacco Root Mountains. Ultramafic metamorphic rocks (formerly harzburgite, lherzolite, and peridotite), 

such as the ultramafic rocks in and near bedrock garnet deposits 

in the northern Greenhorn Range (fig. 38; mountains south of 

Alder Gulch) and in the Section 36 deposit (fig. 42; southwest 

of Sweetwater Basin), also occur in the southern Tobacco Root 

Mountains. On the basis of their geochemistry, the protolith 

of the ultramafic metamorphic rocks in the Tobacco Root 

Mountains is interpreted to be an ultramafic cumulate rich in 

orthopyroxene resulting from a magmatic event in a continental 

setting (Johnson and others, 2004). Although such rocks do not 

appear to be an important component of the metamorphic suite 

in the southern Tobacco Root Mountains at a scale of 1:62,500 

(Vitaliano and others, 1979), they are relatively common in the 

northern Greenhorn Range (Weir, 1982) and adjacent to the Section 36 deposit.

Alaska

Nearly perfect dark-red almandite, called Wrangell 

garnet after the nearest town, which is on Wrangell Island, 

occurs in schist near the east side of the mouth of the Stikine River, 12 km north of Wrangell (Bressler, 1950) in the 

Wrangell Mining District (fig. 46). The schist is part of the 

Wrangell-Revillagigedo belt of regionally metamorphosed 

rocks on the west side of the Coast Range batholith. The area 

is known for its gem-quality garnets but less well known as 

a source of industrial garnet. The garnets were mined for 

abrasives intermittently since before 1910, but little garnet 

has been mined in the area since about 1925. The amount 

of industrial garnet produced is not recorded but was most 

likely small. The garnet deposit was included in studies of 

the Wrangell Mining District (Wright and Wright, 1908; 

Buddington and Chapin, 1929), but actual discovery by gold 

prospectors as early as 1862 is likely. Five of the most promising claims at Garnet Creek belong to the Alaska Garnet 

Mining and Manufacturing Co. Two of these claims near 

the mouth of Garnet Creek are estimated to contain 79,570 

m3 of schist grading 4.85 to 9.26 weight percent garnet. The 

garnets are as much as 4.4 cm across, are dark red, have a 

specific gravity of 4.1 and a hardness of 7.5 Mohs, fracture 

parallel to schistosity, and contain many inclusions of quartz, 

which make most of the garnet unsuitable for gems and, possibly, for abrasive applications.

Brooks (1910) mentioned small shipments of garnet from 

the Wrangell Mining District in 1910. In 1982, a garnet lode 

deposit east of Wrangell and several garnet-bearing beach sand 

deposits were investigated as possible sources of garnet for 

abrasives and filtration media (Pittman, 1984).

On the south side of Port Houghton in the Juneau Mining 

District, about 90 km northwest of Wrangell, is a 10-km-wide 

zone of garnetiferous quartz-mica schist (fig. 46) that contains 

red garnets, as large as 1 cm across, which compose 10 to 

20 volume percent of the rock in especially rich zones and, 

locally, garnetite layers. The garnets have been subjected to 

dissolution, as indicated by truncation of growth zones in the 

crystals. Staurolite and kyanite are minor components.

Andradite in the Ketchikan Mining District, south of the 

Wrangell Mining District, forms the principal gangue mineral in 

contact-metamorphic deposits and occurs mostly in limestone 

in the contact aureoles (fig. 46; Wright and Wright, 1908). The 

garnet is massive or occurs in dodecahedral aggregates. The 

garnet crystals are zoned, ranging in size from 1 to 5 cm across. 

At Coppermount, andradite forms a massive belt of garnetite, 7 

to 15 m wide, between diorite and the limestone host. Included 

in the garnet are small nodules consisting of chalcopyrite, magnetite, pyrrhotite, and pyrite.

In 1987, industrial-grade garnet was produced as a byproduct of processing beach sand for gold along the Gulf of Alaska 

(fig. 47; Pittman, 1989). In 1989, a small strandline gold placer 

operation near Yakataga on the Gulf of Alaska also uncovered 

concentrations of garnet and ilmenite (Pittman, 1991).

The Continental Shelf adjacent to Alaska, including the areas 

off southeastern Alaska and along the Gulf of Alaska, the Bering 

Sea, the Chukchi Sea, and the Beaufort Sea (fig. 47; Beauchamp 

and Cruikshank, 1983), has a potential for placer gold deposits. 

Although offshore placer gold is of principal interest in Alaska, 

placer deposits in which gold occurs may contain other marketable heavy minerals, including ore minerals of antimony, copper, 

lead, platinum, silver, tin, tungsten, and zinc. Beauchamp and 

Cruikshank (1983) suggested that industrial heavy minerals may 

be present in association with offshore placer gold, as in Oregon 

(see below). Although garnet is not mentioned in their report, 

garnet would be expected in Alaskan heavy-mineral suites. Thus, 

although the following discussion focuses on gold, the presence 

of heavy minerals, including garnet, is implied.

The eastern Bering Sea adjacent to western Alaska may 

have the greatest potential for placer gold of any area in the 

United States (fig. 47). Onshore placers, which have produced 

about a third of the gold in Alaska, probably supplied gold to 

beach and offshore sediment. The shelf areas off Nome and 

Goodnews Bay and from 15 km west of Nome to Cape Nome 

21 km east of Nome seem especially promising. Other areas 

important for placer gold include a shoal north-northeast of 

Cape Prince of Wales in the Chukchi Sea; the offshore area 

around Sledge Island, several kilometers west of Nome; cliffs 

once mined for gold and silver near Bluff, 76 km east of Nome; 

and the areas off the Southeast Cape on St. Lawrence Island 

and off the west end of the island. Other areas where onshore 

lode deposits of gold occur near the Continental Shelf merit 

attention, including Captains Bay, the Aleutian Islands, the 

shelf west of Kodiak Island, around Unga and Popof Islands, 

the lower part of Cook Inlet in Kamishak Bay, the shelf adjacent to the southern part of the Kenai Peninsula, and Resurrection Bay near Seward. Reimnitz and Plafker (1976) reported 

concentrations of gold in beach sediment of the Copper River 

Delta. Much of the shelf in the Gulf of Alaska is underlain 

by gold-bearing glacial deposits of the Yakataga Formation. 

Locally intense glaciation, large lode gold occurrences, and 

extensive drainage onto the Continental Shelf suggest that the 
40 U.S. Industrial Garnet

Figure 46. Southeastern Alaska, showing locations of onshore garnet deposits (adapted from Wright and Wright, 1908).

Map area

.Wrangel

56 | o

132 o 134 o

136 o

|

|

|

| | ||+

60 o

58o

56o | | |

| | | | | JUNEAU

DISTRICT

SITKA

DISTRICT

WRANGELL

DISTRICT

KETCHIKAN

. Port Houghton

.

|

.Ketchikan

.Petersburg

| |

+

+ Mt.Wrangell

3750

+

Garnet Mtn.

3610

Phyllite, quartz phyllite, foliated quartzite,

argillaceous and micaceous phyllite and

locally slate

Crystalline schist, gneiss, and phyllite

with intercalated marble

Hornblendite

Quartz diorite, granodiorite, and related 

rocks

Babbler Point

_ Gerard Point

Simonof Island

Point Highfield

Wrangell

Liesnoi Island

Five Mile island

Kadin

Island

Green Point

Sergief Island

Point Rothsay

ph qd

hb

sgp

ph

hb

qd

ph

qd

qd

qd

qd

qd

qd

sgp

qd

ph

EXPLANATION

DISTRICT Coppermount
41

shelf areas near Juneau may be favorable for placer gold deposits and, by inference, heavy minerals, including garnet. The 

heavy-mineral placers about 50 km northeast of Cape Prince of 

Wales have produced minerals containing lead, silver, tin, and 

tungsten (fig. 47).

California

Small amounts of garnet, principally grossularite, were 

produced from tungsten mill tailings in the Bishop Mining 

District in Inyo County from 1938 to as late as 1950 by Huntley Industrial Minerals, Inc. (fig. 48; Braun, 1950; California 

Division of Mines staff, 1950). The garnet was marketed for 

abrasive blasting. In 1954–55, industrial garnet was produced 

by Otis A. Kittle & Associates, Ltd., as a byproduct of a tungGulf of Alaska

Shelikof Strait

Resurrection Bay

Cook Inlet -

Goodnews BayBering Sea

Chukchi Sea

Arctic Ocean

Arctic Ocean

Beaufort Sea

-

0 100 200 KILOMETERS

|

V

N

. . .

Se

_

ward

X

X

X

X ) -

X

Captains Bay _

Kotzebue.

Barrow

Dillingham

Kamishak Bay_

Kodiak

X

Bothol

.

Figure 47. Sketch map of Alaska, showing locations of offshore areas with possible heavy-mineral potential. Thick red 

lines and Xs, parts of shelf with possible potential for gold and platinum; ore minerals for antimony, copper, lead, silver, tin, 

tungsten, and zinc; and heavy minerals including garnet. Small blue area northeast of Cape Prince of Wales has produced 

minerals containing lead, silver, tin, and tungsten. Dots, cities and towns; star, State capital.

U.S. Garnet Deposits

sten mine, also in the Bishop Mining District, and shipped to 

the U.S. Navy in Oregon (California Mining Journal, 1954). 

Operations at the processing plant, located 10 km from Bishop, 

consisted mainly of dry screening, conveying, and sacking. The 

product contained 75 weight percent highly abrasive, dense 

garnet. By May 1, 1954, the company had shipped 39 railroad 

cars containing an estimated 2,000 t of concentrate.

Localities in 26 counties (fig. 48) were reported to 

contain several varieties of garnet, including almandite; 

topazolite (a greenish-yellow to yellow-brown variety of 

andradite); melanite (a black variety of andradite); aplome (a 

dark-brown, yellowish-green, or brownish-green variety of 

andradite); green andradite; essonite (a yellow-brown or reddish-brown transparent variety of grossularite); green, opaque 

white, and colorless grossularite; spessartite; and uvarovite 

(see Murdoch and Webb, 1956).
42 U.S. Industrial Garnet

Figure 49. County map of Nevada, showing county 

boundaries and locations of counties (names in all caps) 

with garnet deposits or occurrences. Dots, cities and 

towns; star, State capital. Xs, garnet localities.

0 50 100 KILOMETERS

INYO

Bishop Mining District

0 50 100 KILOMETERS

| V

N

)

Figure 48. County map of California, showing county boundaries 

and locations of counties (names in all caps) with garnet deposits or 

occurrences. Dots, cities and towns; star, State capital.

Nevada

Garnet-rich rocks are recorded from two localities in 

White Pine County (fig. 49). Small amounts of garnet were 

produced for mineral-supply houses and tourists at Garnet Hill, 

about 8 km northwest of Ely (Smith, 1976). The garnet was 

obtained from the walls of vesicles in rhyolite and panned from 

soil nearby. Another garnet occurrence is on the east flank of 

Mount Moria in the Snake Range, about 65 km east of Ely. The 

garnet is contained in quartz-garnet-mica-staurolite schist that 

makes up part of the canyon walls and forms alluvial deposits 

along Hampton Canyon (Castor, 2003). Test lots of almandite 

for use as an abrasive were produced from this area. Darkbrown spessartite occurs at several other localities in White 

Pine County. Many skarn deposits in Nevada are rich in garnet, 

such as in the Yerrington Mining District in Lyon County.

New Mexico

The skarn deposits of southern New Mexico are in the 

Basin and Range Province, south of the Colorado Plateaus 

Province, and west of the Great Plains (Lueth, 1996). The 

entire Paleozoic section rests unconformably on metamorphosed Late Proterozoic rocks. The Lower Paleozoic section 

is dominated by dolomite and clastic sedimentary rocks. 

The Upper Paleozoic rocks are shelf carbonates that grade 

upsection into clastic rocks. The Mesozoic section consists 

of terrigenous clastic rocks and sedimentary rocks reflecting 

Cretaceous marine incursions. The garnet deposits formed 

adjacent to polyphase granites that range in age from Late 

Cretaceous to Miocene. The Cenozoic rocks are largely volcanic and volcaniclastic rocks that cover older rocks and may 

conceal some garnet deposits. Tertiary and Quaternary extensional tectonics, especially the Rio Grande Rift, were superimposed on compressional tectonism of the Laramide orogeny 

and younger volcanic arcs of the Sierra Madre Occidental and 

Mogollon-Datil volcanic provinces. Tertiary block faulting 

exposed garnet deposits on both sides of the Rio Grande Rift 

and in the Basin and Range Province of New Mexico.

Royalstar Resources, Ltd., began limited garnet production from skarn at their San Pedro Mine in the New Placers 

Mining District in Santa Fe County (fig. 50) sometime before 

1992. Proven reserves are reported as 7 million to 8 million t 

containing 85 weight percent andradite (Lueth, 1996). The 

company ended 1993 with its garnet operation on standby, 

owing to legal difficulties: the County Planning Commission 

insisted that Royalstar obtain a new mining permit under the 

county’s recently adopted mining regulations (U.S. Bureau 
43

Figure 50. County map of New Mexico, showing county boundaries 

and locations of counties (names in all caps) with garnet deposits. 

Dots; cities and towns; star, State capital. Circles, skarn deposits.

U.S. Garnet Deposits

SOCORRO

oo

o

oo o

oo

o o

o o

o

o o

oo o

o

o o o

. Truth or Consequences

Alamagordo

Carlsbad

Silver City

Lordsburg

GRANT

HIDALGO

Deming

LUNA DONA

ANA

SIERRA

OTERO

|

Hanover-Fierro Mining District

SANTA FE

Santa Fe

Albuquerque

Las Cruces

0 50 100 KILOMETERS

of Mines staff, 1993–94b), while Royalstar insisted that their 

earlier permit should be “grandfathered” in. In 1996, when 

San Pedro Mining Corp. applied for and received a mining 

permit from the New Mexico Department of Energy, Minerals, and Natural Resources to reprocess mine dumps at the 

San Pedro Mine for industrial garnet, the corporation still 

needed a mining permit from the Santa Fe County Mining 

Commission, which claimed that mining was not an appropriate use of the area (U.S. Bureau of Mines staff, 1995). No 

industrial garnet production in the State was noted from 1996 

to 2003 (U.S. Geological Survey staff, 1997, 2002b, 2003). 

From 2000 to 2003, at least one company was reportedly 

examining other parts of the State for potential resources of 

industrial garnet (U.S. Geological Survey staff, 2002b, 2003, 

2004, 2005b).

Industrial-grade andradite and grossularite occur in skarn 

in southern and central New Mexico and are major constituents of tailings piles from metal mining (see Lueth, 1996). The 

garnet occurs in various skarn types, including copper, porphyry copper, lead-zinc, iron, and tungsten (Einaudi and others, 

1981), in Upper Paleozoic limestone. The largest garnet deposits are in copper skarn associated with Cretaceous porphyry 

copper deposits in southwestern New Mexico. The garnet 

ranges in composition from pure andradite at igneous contacts 

to pure grossularite in metamorphic pods; compositions generally average greater than Ad80. The garnets range in size from 

1 to 100 mm across, averaging about 4 mm across. Garnet near 

postmineralization faults shows retrograde metamorphism and 

is commonly altered to clay and epidote. The next-largest type 

of garnet deposit is associated with lead-zinc skarn, mostly 

in the Hanover-Fierro Mining District, about 20 km northeast 

of Silver City in Grant County, and in the Orogrande Mining 

District in Otero County. Garnet in these deposits has compositions of Ad10–100, and the rest is spessartite. Garnet grains generally are less fractured in lead-zinc skarn than in copper skarn 

and commonly have reverse zonation, small grain size, fewer 

inclusions, and widely varying composition. The best-quality 

garnet is in iron skarn, the least abundant type of skarn. Iron 

skarn also occurs in the Hanover-Fierro and Orogrande Mining 

Districts. The garnet grains in the iron skarn resemble those in 

the copper skarn but are less fractured and zoned. Past metalmining efforts commonly left barren garnetite at the surface. 

The Iron Mountain Mining District (beryllium and tungsten 

skarn/sulfides) in Sierra and Socorro Counties also has large 

resources of andradite garnet (Jahns, 1944). Skarn layers, as 

much as 30 m thick, are exposed for as much as 3 km along 

strike. Layers of garnetite, as much as 4 m wide, average 70 

weight percent garnet. These deposits can be mined by openpit methods. Deeper garnetite is also minable where previous 

mining left underground workings.

Garnets in southwestern New Mexico formed during two 

stages of skarn formation: (1) isochemical contact metamorphism associated with initial magmatic emplacement and (2) 

the metasomatic main stage of skarn formation associated 

with exsolution of magmatic fluids and influx of meteoric 

water. Calcic skarn in Late Paleozoic shelf carbonates hosts 

the garnet deposits, in contrast to the unmineralized dolomite 

in the Lower Paleozoic section. A late stage in skarn evolution includes retrograde alteration, which destroys garnet, and 

extensive sulfide deposition.

A study was made to determine whether garnet and sphalerite in the Hanover mill tailings ponds could be recovered to 

offset some of the cost of remediation (see Cetin and others, 

1996). The mill is located about 20 km northeast of Silver City 

in Grant County. In the early 1980s, accumulated mine and 

mill wastes at the Hanover millsite were identified as potential 

sources of surface and ground-water pollution. The tailings 

contained abundant lead and copper and were the source of air 

release of significant amounts of heavy metals, especially lead. 

In 1996, the tailings were owned by the Mining Remedial 

Recovery Co. (MRRC) of Price, Utah, one of several companies created in 1992 as a result of the Sharon Steel Corp. 

bankruptcy resolution (ACZ Laboratories Inc., 1993). MRRC 

initiated studies of heavy-metal mobility in the tailings and 

concluded that the tailings were geochemically stable. Underlying bedrock consists of limestone intruded by granite, and 

the tailings were rich in acid-neutralizing carbonates. Eolian 

and fluvial release of contaminants, however, could affect 

nearby Hanover Creek and the surrounding soil.

Garnet resources of the five mill tailings ponds totaled 

135,000 t of material containing 20 to 36 weight percent 

garnet. Most of the tailings were produced by the Empire 

Zinc Co., a subsidiary of the New Jersey Zinc Co., during two 
44 U.S. Industrial Garnet

periods of production: 1902–31, 450,000 t of zinc ore; and 

1937–48, 113,000 t of zinc ore. The mill was operated briefly 

during 1974 by UV Industries; later, the mill was bought by 

Sharon Steel. The mill also processed ore from other mines 

in the Hanover-Fierro Mining District, from the Orogrande 

Mining District, and from the Magdalena Mining District 

in central New Mexico. The principal garnet in the tailings 

ponds is andradite accompanied by small amounts of grossularite. Samples of the tailings were reground to free mineral 

grains, chiefly garnet, from gypsum cement. The Pb, Zn, Cu, 

Fe, and Cd sulfides were removed by flotation; then garnet 

was concentrated by gravity from the tailings. However, the 

marketability of the garnet for abrasives and filtration media 

is unlikely because it contains widely distributed impurities 

(inclusions?, alteration products?); grains of appropriate purity 

are too small to use. In addition, the final tailings could be 

considered hazardous waste (Cd, Pb, Zn), requiring further 

treatment by a phosphate process to be made nonhazardous.

When it became clear that the garnet was unmarketable, 

tailings from the four small ponds were moved to the main 

pond, where they were scheduled to be recontoured, stabilized, 

capped, and revegetated. The largest pond was considered 

stable under seismic-load conditions.

Development of the New Mexico andradite/grossularite 

deposits, such as described above, depends on detailed studies of garnet geochemistry, texture, density, angularity, hardness, and resistance to abrasion. Compositional zones within 

the skarn need to be delineated because properties change 

with composition. Garnet from New Mexico, at least in a few 

mining districts, may not have the characteristics of almandite, 

but it may be competitive with abrasive slag, manufactured 

abrasives, silica sand, olivine, and staurolite.

Oregon

Sand in beaches and marine terraces, as much as 65 m 

above sea level, in Coos and Curry Counties was mined for 

gold as early as 1852, and later for platinum and ilmenite 

(fig. 51; Gray and Kulm, 1985; mining began in 1872 according to Griggs, 1945). Gold anomalies (≥0.005 ppm) are still 

detectable offshore at Gold Beach, Sisters Rocks, and along 

the coast from Port Orford northward to Black Rock Point. In 

the early 1940s, black sands were mined chiefly for chromite, 

with byproduct gold and platinum. From the late 1940s to 

1980, focus again was on the gold and platinum, but chromite was stockpiled. Total known production of gold from 

the black sand placers was at least 4,000 troy oz. Black sand 

placers that contain from 10 to more than 30 weight percent 

(max 56 weight percent; Kulm and others, 1968) heavy minerals, including garnet, occur mostly along the coast of Curry 

County discontinuously from Brookings to Bullards Beach 

State Park just north of the mouth of the Coquille River. Some 

of the black sand concentrations include modern beach deposits, as at Boardman State Wayside and in the Gold Beach area 

from the mouth of the Rogue River to the mouth of the Pistol 

River. The most extensive placer deposits are in the Gold 

Beach area from the Pistol River to Sisters Rocks, north of the 

mouth of the Rogue River. On the basis of interpretations of 

magnetometer surveys and the assumption that magnetite in 

the black sands is the primary source of the magnetic anomalies, Kulm and others concluded that the largest and richest 

concentrations of heavy minerals are 2 to 13 km offshore in 

water as deep as 92 m. Less likely, the magnetic anomalies 

are from intrusive or extrusive rocks. Kulm and others (1968) 

completed seven east-west traverses ranging in length from 1 

to 9 km and five north-south traverses ranging in length from 1 

to about 4 km. Gray and Kulm suggested running north-south 

magnetometer-survey lines in the offshore area from 140-m 

depth to the shore to locate buried and (or) submerged stream 

channels that could contain heavy-mineral placers.

The highest concentrations of black sand deposits are on 

the outer margin of the Continental Shelf between the Rogue 

River and Cape Blanco, under 146 to 185 m of water. Samples 

of black sand deposits contained as much as 56 weight percent 

heavy minerals. The deposits on the inner shelf are interpreted 

as relict beach deposits, created during Pleistocene glaciations 

when sea level was lower.

The heavy-mineral black sands of the Oregon coast were 

included in early studies of black sand placer deposits by Day 

and Richards (1906a, b). Garnet was included in the heavymineral suites mentioned in their more detailed publication 

(Day and Richards, 1906b). For their study, they solicited 

samples, generally no heavier than 2 kg, of heavy-mineral 

sand from placer miners. Samples were received from Alaska, 

Arizona, California, Colorado, Idaho, Indiana, Kansas, Maryland, Mississippi, Montana, Nebraska, Nevada, New Mexico, 

New York, North Carolina, Ohio, Oklahoma, many counties 

in Oregon, South Dakota, Texas, Utah, Washington, and Wyoming. In some States, including Oregon, samples several tons 

in size were collected and shipped to a laboratory in Portland 

by railroad carload to take advantage of the free transportation provided by various railroad companies. The “Remarks” 

column of Day and Richards’ (1906b) main table indicates that 

some samples consisted of several tons, but the weight of each 

sample was not mentioned. In addition, many samples came 

from sluiceboxes or were otherwise already concentrated. 

However, some of the sample sets may have some general 

value. Garnet content ranged from 0 to 21.4 weight percent in 

56 samples from Clatsop County, mostly described as “natural 

beach sand.” The highest grade was in a sample near Hammond, located on the south bank of the Columbia River near 

its mouth. Garnet content ranged from 0 to 80 weight percent 

in 21 samples from Coos County. The highest grade was in 

a sample from the old seawall at Randolph, located about 30 

km south of Coos Bay; however, this and most other samples 

from Coos County were described as concentrates. Garnet 

content ranged from 2.7 to 44 weight percent in seven samples 

of beach sand from Lincoln County, from 25.3 to 31.6 weight 

percent in three samples from Yaquina Bay, and from 2.7 to 

24.2 weight percent in three samples from Newport. The data 
U.S. Garnet Deposits 45

Figure 51. Oregon coast, showing locations of beach, offshore, and marine-terrace deposits of black sand and offshore gold 

anomalies (from Gray and Kulm, 1985). Yellow areas with red margins and pale-yellow, red-striped, and transparent area off Cape 

Blanco, anomalous gold (≥0.005 ppm); brown stippled areas, black sand deposits. Darker blue line offshore, limit of U.S. Territory 

(but not of the Exclusive Economic Zone); light-blue area along coast, Continental Shelf; red lines, isopachs of sediment (in meters; 

contour interval, 500 m); darker brown areas in southern part of map, mineralized rock; oval black-crosshatched area, coal deposits. Circles, mines mentioned in text. (Locations may represent more than one mine.)
46 U.S. Industrial Garnet

are unclear whether the high-grade sample (44 weight percent 

garnet) from Toledo was a concentrate or from river sand (fig. 

51). Garnet content ranged from 0 to 55.2 weight percent in 12 

samples from Curry County; the highest grade was in a sample 

from tailings after gold extraction in the Port Orford area. 

Otherwise, the highest grade of black sand from beaches in the 

Port Orford area was 10.3 weight percent garnet. One sample 

from Lane County contained 11 weight percent garnet.

In a later study, beach sands along 70 km of the Oregon 

coast were analyzed for contents of chromite, zircon, garnet, 

and ilmenite (Dasher and others, 1942). Samples were 

obtained from the Shepherd and Pioneer Mines, from two drill 

holes at Coos Bay in Coos County, from the Butler (or Baker) 

Mine north of the Sixes River, and from Ophir Beach near 

the town of Ophir in Curry County. The deposits of interest 

occur in pockets of heavy minerals on the landward side of old 

beaches and inland along creekbeds. Minerals and rock types 

identified in the beach sand include chromite; quartz; chert; 

augite; diopside; hornblende, actinolite, and other amphiboles; 

epidote; zoisite(?); tourmaline; zircon; Fe-rich olivine; manganiferous and Fe-bearing garnet; ilmenite; magnetite and (or) 

chromitiferous and titaniferous magnetite; rutile; and uvarovite. Most of the study focused on determining the size of the 

chromite fraction. With hydraulic tabling before electrostatic 

separation, electrostatic rejects consisted of garnet and zircon, 

with traces of mafic minerals, quartz, rutile, and opaque minerals. The separation could be done by gravity, which can 

easily separate out products that may be of economic value, 

such as garnet and zircon abrasives. The proportion of garnet 

and zircon in the samples varied widely; however, samples 

that produced the largest chromite concentrates also contained 

the largest proportions of garnet and zircon. Grains of garnet 

are generally round, but that shape may not be undesirable 

because rounded garnets can still be used for low-dust airblasting and may be suitable for other applications.

Griggs (1945) studied chromite-bearing sands, including 

beach and marine-terrace deposits, along the Oregon coast 

from about 13 km south of Coquille Point to Coos Bay. Black 

sand deposits on the marine terraces range from less than 0.3 

to 13 m in thickness (avg 2–3 m thick), from several meters to 

more than 305 m in width, and from several hundred meters 

to more than 1,600 m in length. These deposits are covered 

by 0.3 to 25 m of sand, clay, and gravel. Clean garnet concentrate from the black sand consists of round grains, from 0.5 

to 2 mm across. Garnets in samples of black sand deposits 

near the Coquille River include the varieties almandite and 

spessartite. Garnet content ranged from 10.2 to 28.8 weight 

percent in the black sand; three samples contained more than 

25 weight percent garnet. When these deposits were studied, 

roundness of grains, such as in these deposits, was thought to 

eliminate garnet from consideration as an abrasive; the garnet 

was considered worthless. Roundness is not necessarily an 

obstacle to the use of garnet, which has other applications that 

were unknown in 1945. At present, other characteristics of the 

garnet would need to be evaluated in order to determine its 

value. Griggs estimated 1.944 million t of reserves of black 

sand grading on average more than 5 volume percent chromite 

and 1.231 million t of reserves of black sand grading on average 3 to 5 volume percent chromite; he further estimated that 

the beaches contain 101,600 t of black sand grading on average at least 5 volume percent chromite. Griggs’ focus was on 

chromite, and so he did not record in detail the garnet content 

of the black sand deposits he studied. His table 9, however, 

lists the results of 200-grain counts of minerals in 19 samples 

from beaches and marine terraces, of which garnet composed 

1 to 58 grains. These data suggest that garnet concentrations 

are higher in the marine terraces.

Twenhofel (1943, 1946) studied the Oregon coast and 

observed that black sand deposits formed in relatively few 

places. In his first study (Twenhofel, 1943), which focused on 

the south coast from the Oregon State line to Coos Bay, black 

sand deposits were observed near the mouth of Five Mile 

Creek on the beach south of Cape Blanco, in the bay south of 

The Heads at Port Orford, around the mouth of Eucre Creek 

south of the headland of Sisters Rocks, around the mouth of 

the Rogue River, and around the mouths of Meyers Creek 

and the Pistol River in the bay between Cape Sebastian and 

Crook Point. In his second study (Twenhofel, 1946), which 

focused on the coast north of Coos Bay to the north bank of 

the Columbia River, relatively few black sand deposits were 

observed, ranging from 300 to 15,500 m3 in volume, the largest of which were in the Newport area. Total garnet content 

was not estimated. The beach between Hecata Head and Otter 

Rock was judged to be one of the richest in heavy minerals 

along the Oregon coast north of Coos Bay. Garnet contents 

in the black sands along the north coast are as high as 19.6 

weight percent but average much less.

Chromite-bearing beach sands were mined from raised 

beaches of the south coast of Oregon during World War 

II (Clifton and Mason, 1969; McKelvey, 1986). The U.S. 

Department of the Interior’s Continental Shelf Mining Policy 

Task Force (1979) reported large identified offshore resources 

there of chromite (30 million t), gold (6 million troy oz), and 

platinum (350,000 troy oz). The amount of recoverable garnet 

was not mentioned and may not have been studied; however, 

garnet is known to occur in the heavy-mineral sand fractions. 

Other studies of offshore mineral resources indicated areas 

favorable for heavy minerals off the Columbia, Nehalem, 

Siltcoos, and Umpqua Rivers (Phillips, 1979; Beauchamp 

and Cruikshank, 1983). A joint Federal-State task force was 

set up in 1988 to evaluate offshore black sands for chromite, 

ilmenite, zircon, garnet, and gold. The study’s aim was to 

determine the extent of black sand deposits off the coast and 

evaluate their economic and strategic importance. This information would permit the Department of the Interior to make 

informal judgments on the feasibility of commercially extracting key minerals (Rice and Lyons, 1990). This report, if it was 

produced, was not located. In 1992, Oregon Resources Corp., 

a subsidiary of Rare Element Resources Ltd., continued to 

acquire the needed permits and evaluate onshore black sands 

in the Seven Devils area in western Coos County (Minarik, 

1992).
47

Conclusions

Industrial garnet has many valuable properties, such 

as hardness, sharpness, chemical inertness (under most 

surface conditions), and high specific gravity, all of which 

are employed in one or another of its uses. Garnet is also 

recyclable. Despite this assemblage of desirable qualities, 

garnet still has only a minor share of the abrasives market 

(fig. 5). This situation may change as concern increases for 

clean air (airblasting, waterjet cutting) and clean water (filtration media). Waterjet cutting and airblasting are expected 

to have the highest rates of growth (Austin, 1993a); 

worldwide industrial demand was projected to grow at 3 

to 5 percent at least until 1998. As indicated above, world 

garnet consumption increased by about 40 percent between 

1998 and 2004. Demand for garnet abrasive powders used 

for polishing television and computer-monitor screens is 

declining as flat-screen systems that do not need polishing 

take over the market. Worldwide increases in petroleum 

use and cost have stimulated an increase in exploration 

for petroleum. This exploration may be accompanied by 

a possibly increased use of garnet in airblast cleaning of 

drill pipes. Increases in defense spending or domestic passenger-airplane production could increase garnet demand 

in the aircraft and shipbuilding industries, both of which 

use significant amounts of garnet for airblast cleaning and 

finishing of metal surfaces and in waterjet cutting. Even if 

the demand for garnet increases, however, domestic industrial garnet producers will still have to contend with foreign 

garnet that may be more cheaply produced (India, China, 

Australia, Canada). However, as experienced by WGI 

Heavy Metals, Inc. (2005a), in India, government permits 

to mine may require use of cheap, but slower, hand methods. Either at home or abroad, legal issues and geologic 

hazards can eclipse business plans.

Acknowledgments

Material pertinent to this report was obtained from 

Michael L. Zientek, USGS; William M. Kelly, Geological Survey of New York; Christopher Dail, USFS; and 

the Emerald Creek Garnet Co. and its parent company 

WGI Heavy Minerals, Inc. Reviews by Richard Berg 

(Montana Institute of Technology) and by Michael Zientek and Thomas Frost (both of the USGS Spokane Field 

Office) greatly improved the manuscript. Thanks to Wanda 

Edwards and Tony Morris of the USFS, who made facilities 

at Clarkia available during fieldwork and provided access 

to certain restricted areas. Maryanne Besaw of the Idaho 

Department of Lands and Jim Mackay of Potlatch Corp. 

also facilitated access to large parts of the study area in 

northern Idaho. Hart Baitis of Ruby Valley Garnet, LLC, 

provided access to the Red Wash Mine area and the Section 

36 deposit and shared his knowledge with us.

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