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Beal Mountain Mine

Plant in Silver Bow county in Montana, United States with commodities Gold, Silver
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Public Land Survey System information
  6. Commodities
  7. Materials information
  8. Alteration
  9. Mineral occurrence model information
  10. Host and associated rocks
  11. Nearby scientific data
  12. Geologic structures
  13. Ore body information
  14. Controls for ore emplacement
  15. Economic information about the deposit and operations
  16. Mining district
  17. Mineral rights holdings
  18. Land status
  19. Ownership information
  20. Production statistics
  21. Reserves and resources
  22. Workings at the site
  23. Links to other databases
  24. Bibliographic references
  25. General comments
  26. Reporter information

Geologic information

Identification information

Deposit ID 10124641
MRDS ID W026570
MAS/MILS ID 0300930087
Record type Site
Current site name Beal Mountain Mine
Alternate or previous names German Gulch
Related records 10013390

Geographic coordinates

Point of reference Ore Body
Geographic coordinates: -112.8831, 45.95429 (WGS84)
Elevation 2110
Location accuracy 100(meters)

Site location context

Political divisions (FIPS codes)

Silver Bow(county)

Montana(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Dickie Peak(quadrangle 1:24,000 scale)

Butte South(quadrangle 1:100,000 scale)

Dillon(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Upper Clark Fork(hydrologic unit)

Pend Oreille(hydrologic accounting unit)

Kootenai-Pend Oreille-Spokane(hydrologic subregion)

Pacific Northwest(hydrologic region)

Federal lands

Beaverhead-Deerlodge National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country State County
United States Montana Silver Bow

Public Land Survey System information

Meridian Township Range Section Fraction State
Montana Principal 002 N 010 W 06 SENE Montana

Commodities

Commodity Importance
Gold Primary
Silver Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Gold Ore
Sylvanite Ore
Calcite Unknown
Chalcopyrite Unknown
Chlorite Unknown
Molybdenite Unknown
Pyrite Unknown
Pyrrhotite Unknown
Quartz Unknown
Sericite Unknown

Alteration

  • (Local) BLEACHING, CHLORITIZATION, SILICIFICATION, AND MINOR SERICITIZATION.

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46
Model code 64
USGS model code 18f
Deposit model name Skarn Au
Mark3 model number 82

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Metasedimentary Rock > Quartzite
    Rock type qualifier QUARTZITE (SANDSTONES), HORNFELS (MUDSTONES), METACONGLOMERATES
    Rock unit name COLORADO GROUP (?); BLACKLEAF FORMATION; VAUGHN MEMBER
    Stratigraphic age (youngest) Late Cretaceous
  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite
    Rock type qualifier DIORITE DIKES AND PLUGS, GRANODIORITE, ANDESITE TO DACITE DIKES
    Rock unit name BOULDER BATHOLITH
    Stratigraphic age (youngest) Cretaceous

Nearby scientific data

Ore Body (1) -112.8831, 45.95429
ListMap

Economic information

Geologic structures

Type of structure Regional
Structure name FRONTAL FOLD AND THRUST BELT OF THE GRASSHOPPER THRUST SYSTEM,
Type of structure Local
Structure name GERMAN GULCH FAULT, THE BEAL SHEAR, AND SEVERAL NORTHWEST- AND NORTHEAST-TR

Ore body information

  • General form PIPE (NEARLY VERTICAL)
    Strike N00S
    Dip 00S
    Thickness 182M
    Length 200M
    Width 200M
    Area 230HA
    Depth to top 90M
    Field Value
    MAS Matrix # 1
    MAS Column # 1
    Type of Orebody #1 SHEAR ZONE
    Shape of Orebody #1 PIPELIKE
    Primary mode of Origin HYDROTHERMAL
    Primary Ore Control FAULTING
    Secondary Ore Control FRACTURING
    Degree of Wallrock Alter. INTENSE
    Type of Wallrock Alter. #1 SILICIFICATION
    Strike And Dip N00S:00S
    Minimum Depth to Top 1
    Avg. Thick. Unconsol. Mat. 3
    Min. Thick. Unconsol. Mat. 0
    Total Surface Area (HA) 230
    Future Surface Area (HA) 22
    Previous Surface Area (HA) 111
    Reclaimed Surface Area (HA) 0
    Date of Last Modification 980227

Controls for ore emplacement

  • N80E FAULTS

Comments on the geologic information

  • MAJOR STRUCTURES IN THE AREA INCLUDE THE GERMAN GULCH FAULT, THE BEAL SHEAR, AND SEVERAL NORTHWEST- AND NORTHEAST-TRENDING FAULTS (HASTINGS AND HARROLD, 1988).

    MAJOR STRUCTURES IN THE AREA INCLUDE THE GERMAN GULCH FAULT, THE BEAL SHEAR, AND THE GULLY FAULT. THE GERMAN GULCH FAULT, THOUGH NOT EXPOSED, HAS BEEN INFERRED FROM OFFSETS MAPPED ALONG THE VOLCANIC-INTRUSIVE AND INTRUSIVE-METASEDIMENT CONTACTS.

    THE BEAL SHEAR IS A N80-85 DEG W, 85-90 DEG SOUTH-DIPPING ZONE OF BRECCIATION AND FRACTURING THAT WAS ACTIVE PRIOR TO, AND FOLLOWING EMPLACEMENT OF THE DIORITE INTRUSIVE. LARGE, COHERENT BLOCKS OF METASEDIMENTARY ROCKS ARE COMMON IN THE MAIN PORTION OF THIS ZONE WHICH MAY EXCEED 21 M (70 FT) IN WIDTH. WESTWARD, THE BEAL SHEAR NARROWS AND HORSETAILS INTO NUMEROUS SMALLER STRUCTURES AS IT CONTINUES THROUGH AND BEYOND THE DIORITE INTRUSIVE.

    THE VERTICAL TO STEEPLY EAST-DIPPING GULLY FAULT FORMS THE EASTERN MARGIN OF THE DEPOSIT. THIS STRUCTURE IS MINERALIZED AND OFFSETS THE BEAL SHEAR, WHICH BECOMES LESS PRONOUNCED EASTWARD. (HASTINGS AND HARROLD, 1988)

    STRUCTURES WITHIN THE BEAL DEPOSIT CONSIST OF THE BEAL SHEAR AND RELATED FRACTURE ZONES, THE GULLY FAULT, BEDDING FAULTS, WEST HIGHWALL THRUST FAULT, AND THE NORTHEAST NORMAL FAULT. THE BEAL SHEAR IS LOCATED WITHIN THE SOUTHERN PORTION OF THE BEAL DEPOSIT AND REPRESENTS A BRECCIATED AND FRACTURED ZONE WHICH STRIKES N80 DEG TO 90 DEG W AND DIPS 70 TO 80 DEG. S. THE WIDTH OF THE ZONE VARIES FROM 70 TO 120 FEET AND CUTS THE WEST HIGHWALL DIORITE HORSETAILING OUT FROM THE DIORITE HANGING WALL IN THE METASEDIMENTS TO THE WEST...... THE BEAL SHEAR APPEARS TO BE A MAJOR CONDUIT FOR GOLD-BEARING SOLUTIONS.

    THE GULLY FAULT IS A NORMAL FAULT STRIKING N 45 DEG TO 55 DEG W, DIPPING 85 DEG TO 90 DEG SW. DISPLACEMENT IS 20-25 FT (6.1-7.6 M) WITH THE SOUTHWEST BLOCK DOWN-DROPPED. FAULT GOUGE IS A MAXIMUM OF 20 FT (6.1 M) WIDE AND CONSISTS OF LIMONITE TO HEMATITIC CLAYS WITH BRECCIATED METASEDIMENT FRAGMENTS. THE FAULT IS MINERALI
  • HOST ROCKS FOR THE BEAL GOLD DEPOSIT ARE THICK-BEDDED TO LAMINATED, GENTLY NORTH-DIPPING (10 DEG TO 15 DEG) KOOTENAI-COLORADO FORMATION SANDSTONES, MUDSTONES AND CONGLOMERATES THAT HAVE BEEN CONTACT METAMORPHOSED TO PYROXENE-HORNFELS FACIES QUARTZITES, HORNFELSES AND METACONGLOMERATES. THE METAMORPHIC MINERAL ASSEMBLAGE INCLUDES BIOTITE, DIOPSIDE, POTASSIUM FELDSPAR, CHLORITE, SCAPOLITE, QUARTZ, ACTINOLITE-TREMOLITE, AND HORNBLENDE. CONTACTS BETWEEN THE LITHOLOGIC UNITS ARE COMMONLY GRADATIONAL AND SEDIMENTARY FEATURES HAVE NOT BEEN DESTROYED BY METAMORPHISM

Economic information about the deposit and operations

Operation type Surface
Development status Plant
Commodity type Metallic
Deposit size Small
Significant Yes
Discovery year 1864
Mining method Open Pit
Year of first production 1989
Plant type Leach
Plant subcategory Hydromet
Milling method Heap Leach-Agglomerate-Carbon Column-Electrowin

Comments on exploration

  • EARLY MINERS ASSOCIATED WITH PLACERS DISCOVERED LODE DEPOSITS IN AREA.

    1932-33-WINSTON BROTHERS COMPANY OPTIONED AND TESTED AREA.

    1936-39-ANACONDA COMPANY EXPLORED AS A LODE DEPOSIT.

    1968-83-EXPLORED BY U.S. SMELTING AND REFINING CO. (SHARON STEEL CORPORATION) WITH GEOLOGICAL MAPPING, GEOCHEMICAL SAMPLING, GEOPHYSICAL SURVEYING, AND LIMITED DRILLING ON THE ?CHICKEN? CLAIMS.

    1973-76-EXPLORED AS AN OPEN PIT BY PLACER AMEX WHO OPTIONED GROUND AND CONDUCTED GEOCHEMICAL SAMPLING AND DRILLING.

    1980-1983-MONTORO GOLD EXPLORED THE DEPOSIT.

    1983-1984-PEGASUS GOLD CORP. (BEAL MINING COMPANY) ACQUIRES MAJORITY INTEREST IN PROPERTY FROM MONTORO AND SILVER SEAL (SHARON STEEL CORPORATION?).

    1984-85-PROJECT PUT ON HOLD; DISCONTINUE FURTHER DEVELOPMENT.

    1988-PERMITS APPLIED FOR BY PEGASUS GOLD IN FEBRUARY/CONSTRUCTION BEGINS IN JULY/LEACHING IN NOVEMBER.

    1989-FIRST GOLD POUR.

    1993-SOUTH BEAL DEPOSIT LOCATED (~55,000 OUNCES OF GOLD, 700,000 TONS OF MINABLE RESERVES).

    1996-MAIN PIT MINED TO MAXIMUM PERMITTED DEPTH, STARTED TO BACKFILL WITH WASTE FROM SOUTH PIT.

    OCTOBER 1997-SOUTH BEAL (SHARON STEELE) OREBODY COMPLETED.

    1998-2000-RECLAMATION AND DECOMMISSIONING OF LEACH PAD

Mining district

District name Siberia District

Mineral rights holdings

Type of mineral rights Located Claim

Land status

Ownership category National Forest

Ownership information

  • Type Owner-Operator
    Owner Pegasus Gold Inc.
    ID 2470115
    Interest 100
    Home office Washington
    Year 1991
  • Type Operator
    Owner Beal Mountain Mining Inc.
    Home office Montana

Production statistics

  • Year 1989
    Description Annual Gold Production 1157 Kg Of Au
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1157000g
  • Year 1990
    Description Annual Gold Production 1555 Kg Of Au
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1555000g
  • Year 1991
    Description Ag 7200 Oz
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Silver Silver 203292g
  • Year 1991
    Description Au 47305 Oz
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1335656g
  • Year 1992
    Description Silver Production 7971 T Oz/Yr
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Silver Silver 225061g
  • Year 1992
    Description Gold Production 52212 T Oz/Yr
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1474205g
  • Year 1993
    Description Silver Production 8600 T Oz/Yr
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Silver Silver 242821g
  • Year 1993
    Description Gold Production 59300 T Oz/Yr
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1674335g
  • Year 1994
    Description Silver Production 8700 T Oz/Yr
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Silver Silver 245644g
  • Year 1994
    Description Gold Production 61200 T Oz/Yr
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1727982g
  • Year 1995
    Description Silver Production 1995 9-Months 7024 T Oz/Yr
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Silver Silver 198322g
  • Year 1995
    Accuracy Estimate
    Description Gold Production (Full Year Est) 59900 T Oz/Yr Gold
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1691276g
  • Year 1996
    Description Gold Production 45000 T Oz/Yr Gold
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 1270575g
  • Year 1996
    Description Silver Production 7800 T Oz/Yr Silver
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Silver Silver 220233g
  • Year 1997
    Period 1989-1997
    Material ore
    Ore mined 13000000mt
    Accuracy Accurate
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Minor AG Silver Silver 2306634.15g
    Major AU Gold Gold 13775731.73g

Comments on the production information

  • 1988 TO ~1992-250,000 OUNCES (7.8 TONS) PRODUCED WITH AN AVERAGE GRADE OF 0.47 OPT (1.6 G/T) AND RESERVES AT THAT TIME WERE ESTIMATED AT 9.8 MILLION TONS.

    THE AVERAGE GRADE AT THE MAIN BEAL PIT WAS 0.045 OPT AU; AT THE SOUTH PIT IT WAS 0.06 OPT AU. (R.B. MCCULLOCH, 2000, MBMG, BUTTE, PERS. COMM.)



    1989-37,200 OUNCES AU; 8,100 OZ AG.

    1990-50,000 OUNCES AU; 9,800 OZ AG.

    1991-47,300 OUNCES AU; 7,800 OZ AG

    1992-52,200 OUNCES AU; 8,000 OZ AG.

    1993-59,300 OUNCES AU; 8,600 OZ AG.

    1994-61,200 OUNCES AU; 8,700 OZ AG

    1995-59,880 OUNCES AU; 10,200 OZ AG.

    1996-45,067 OUNCES AU; 7,834 OZ AG.



    CYANIDE HEAP-LEACH WITH AGGLOMERATION; RECOVERED BY CARBON ADSORPTION, CARBON STRIPPING, ELECTROWINNING, AND REFINING.



    THE BEAL AND SOUTH BEAL DEPOSITS ARE CONSIDERED LOW-GRADE PRECIOUS METAL, OPEN PIT BULK MINABLE AND HEAP LEACHABLE RESERVES. (FIER, 1992)

Reserves and resources

  • Type In-situ
    Estimate year 1991
    Measured 10184963mt ore
    Demonstrated 10184963mt ore
    Total resources 10184963mt ore
    Commodity Subtype Grade units Group Importance Year
    Gold Au 1.73 g/mt Gold Major 1991
    Silver Ag 0.56 g/mt Silver Minor 1991
  • Type In-situ
    Estimate year 1991
    Demonstrated 10200000mt ore
    Total resources 10200000mt ore
    Commodity Subtype Grade units Group Importance Year
    Gold Au 1.714 g/mt Gold Major 1991
  • Type In-situ
    Estimate year 1996
    Demonstrated 1828000mt ore
    Total resources 1828000mt ore
    Commodity Subtype Grade units Group Importance Year
    Gold Au 1.58 g/mt Gold Major 1996
    Silver Ag 3.43 g/mt Silver Minor 1996
  • Type In-situ
    Estimate year 1997
    Demonstrated 637000mt ore
    Commodity Subtype Grade units Group Importance Year
    Gold Au 2.09 g/mt Gold Major 1997

Comments on the reserve resource information

  • PROVEN + PROBABLE RESERVES; 12/31/96; COG OF 0.62 G/MT SR OF 5.3:1.0; SILVER GRADE BASED ON 1996 SILVER RECOVERED:

Workings at the site

  • Type of workings Surface
    Area 133HA
    Field Value
    MAS Development Schedule # 1
    Mining Record # 1
    Status of Mining Method ESTIMATE
    Mining Method OPEN PIT
    Swell Factor .67
    Percent Waste Rock 30.5
    Avg. Overburden Thickness 90
    Primary Material Cover SAND, GRAVEL
    Hardness of Ore M-HARD ROCKS
    Avg. Bench Height (meters) 6
    Max. Pit Slope (degrees) 45
    Capacity 8374
    Capacity Units MT ORE/DAY
    Preprod. Stripping Vol. 301
    Unit Production Cost .89
    Units of Production $/MT ORE
    Operating Days per Year 195
    Operating Shifts per Day 3
    Year of Information 1991

Comments on the workings information

  • MAIN BEAL PIT AT 6,920 FT; LEACH PAD AT 7,500 FT; PROJECT AREA ELEVATIONS RANGE FROM 2,100 TO 2,400 M (6,900 TO 7,860 FT). STEEP, TREE-COVERED, NORTH-FACING SLOPES AND OPEN SOUTHERLY EXPOSURES.

    THIS IS CONSIDERED TO BE A HIGH ALTITUDE DEPOSIT IN STEEP, TREE-COVERED TOPOGRAPHY WITH THE CONTINENTAL DIVIDE LOCATED ON THE SOUTHERN BOUNDARY OF THE PROPERTY (FIER, 1992).

    CONTINENTAL DIVIDE IS ABOUT 1 MI SOUTH OF THE MINE. (ACCORDING TO THE LAND STATUS MAPS, THE PROPERTY DOES NOT BORDER THE DIVIDE.)
  • 1932-1933 THERE WERE 2,000 FT OF UNDERGROUND WORKINGS.

    OPEN PIT ON SITE OF EARLIER HYDRAULIC WASHING FOR PLACER GOLD.

Reference information

Bibliographic references

  • Production

    PEGASUS GOLD INC., 1995 ANNUAL REPORT, P6.

  • Geology

    HASTINGS, J.S., AND HARROLD, J.L., 1988, GEOLOGY OF THE BEAL GOLD DEPOSIT, GERMAN GULCH, MONTANA IN: BULK MINEABLE PRECIOUS METAL DEPOSITS OF THE WESTERN UNITED STATES; SYMPOSIUM PROCEEDINGS, R.W. SHAFER, J.J. COOPER AND P.G VIKRE (EDS.): GEOLOGICAL SOCIETY OF NEVADA, P. 207-220

  • Reserve-Resource

    PEGASUS GOLD INC., 1995 FORM 10-K, P9.

  • Reserve-Resource

    PEGASUS GOLD INC., 1996 ANNUAL REPORT, PP. 6-7, & FORM 10-K

  • Reserve-Resource

    REPORT, PP. 8, 17-18.

  • Deposit

    BANISTER, D. P. GERMAN GULCH, SILVER BOW COUNTY, MONTANA. BUMINES HEAVY MINERALS SITUATION REPORT NO. 57, MARCH 1969, 10 PP.

  • Deposit

    BEAL MOUNTAIN MINING INC. (PEGASUS GOLD CORP.). APPLICATION FOR A HARD ROCK OPERATING PERMIT, BEAL MOUNTAIN PROJECT, SILVER BOW COUNTY, MONTANA. FEBRUARY 1988.

  • Deposit

    LAWSON, D. C. DIRECTORY OF MONTANA MINING ENTERPRISES FOR 1990. MONTANA BUREAU OF MINES AND GEOLOGY, BULL. 129, 1990.

  • Deposit

    LYDEN, C. J. THE GOLD PLACERS OF MONTANA. MONTANA BUREAU OF MINES AND GEOLOGY, MEM. NO. 26, 1948, P. 142.

  • Deposit

    MUNDSTOCK, W. GERMAN GULCH MINING OPERATIONS MAY START BY THIS FALL, SAYS PEGASUS OFFICIAL. WALLACE MINER. FEBRUARY 11, 1988, P. 2.

  • Deposit

    NORTHERN MINER (TORONTO, CANADA). PEGASUS DOUBLES ORE RESERVES AT MONTANA LEACHING PROJECT. JANUARY 17, 1985.

  • Deposit

    PEGASUS GOLD INC. ANNUAL REPORTS, 1986 - 1990.

  • Deposit

    SAHINEN, U. M. MINING DISTRICTS OF MONTANA; A THESIS. MONTANA SCHOOL OF MINES, BUTTE, MT, 1935, P. 91.

  • Deposit

    WALENGA, K. $13.2 MILLION PROJECT WON PERMITS IN RECORD TIME. ROCKY MOUNTAIN PAYDIRT, MARCH 1989, PP. 4A-5A.

  • Deposit

    MONTANA STANDARD. MEETING THURSDAY ON BEAL AMENDMENT.FEB. 2, 1992.

  • Deposit

    MONTANA STANDARD. MINING COMPANY WANTS TO EXPAND OPERATIONS. JAN. 21, 1992.

  • Deposit

    MONTANA STANDARD. PEGASUS PLANS BEAL EXPLORATION.APRIL 5, 1992.

  • Deposit

    PEGASUS GOLD INC., 1991 ANNUAL REPORT, P. 4,5,11,12, 1992.

  • Deposit

    MINING RECORD. PEGASUS INCREASES RESERVES 14% IN 3 MONTHS. VOL.106N/13. MARCH 29, 1995.

  • Deposit

    THE MINING RECORD, VOL 107, #34, AUG. 21, 1996, P19.

General comments

Subject category Comment text
Deposit DEPOSIT IS LIMITED BY A PROMINENT NORTHWEST-TRENDING FAULT ON THE EAST AND BY A METADIORITE INTRUSIVE ON THE WEST (HASTINGS AND HARROLD, 1988).

SULFIDE AND PRECIOUS METAL MINERLAIZATION AT THE BEAL DEPOSIT OCCURS PRIMARILY AS DISSEMINATIONS WITHIN FAVORABLE LITHOLOGIC HORIZONS, AND TO A LESSER EXTENT IN NARROW CROSS-CUTTING VEINS CONTAINING QUARTZ, CHLORITE AND CALCITE. (HASTINGS AND HARROLD, 1988).
General THIS SITE IS APPARENTLY SOURCE FOR GERMAN GULCH PLACERS. ; INFO.SRC : 3 FIELD OBSERV
Deposit GOLD OCCURS AS NATIVE GOLD. GOLD IS ALSO ASSOCIATED WITH DISSEMINATED SULFIDE MINERALS (MAINLY PYRITE AND CHALCOPYRITE) IN QUARTZITE BEDS. ALSO, REPORTED LEAD-BISMUTH TELLURIDES. THE GOLD-SILVER RATIO IS 1:1 AT THE MAIN BEAL PIT; 5:1 AT THE SOUTH BEAL PIT (HASTINGS AND HARROLD, 1988).
Deposit GOLD GRADES IN ?CLASTIC SKARN? DEPOSITS LOCALLY ARE ENHANCED WHERE QUARTZITE BEDS ARE CUT BY MINERALIZED DIORITE DIKES AND QUARTZ-SULFIDE-TELLURIDE VEINS.

RETROGRADE MINERALIZATION IS LOCATED ALONG FRACTURES AND VEINLETS AND MAY REPRESENT REMOBILIZATION OF PROGRADE SULFIDE AND PRECIOUS METALS OR POSSIBLY ANOTHER MINERALIZING EVENT. (FIER, 1992).
Deposit ALTERATION AT THE BEAL DEPOSIT IS CHARACTERIZED BY BLEACHING, CHLORITIZATION, SILICIFICATION, AND MINOR SERICITIZATION. THE ALTERATION ASSEMBLAGE IS REPRESENTED BY CHLORITE, QUARTZ, CLAYS (SMECTITE, NONTRONITE AND KAOLIN), CARBONATE AND SERICITE. BLEACHING IS MOST EVIDENT AT INTRUSIVE CONTACTS AND ADJACENT TO MOST CROSS-CUTTING VEINS. ALTERED HORNFELSES ARE WHITE, LIGHT GRAY OR LIGHT BROWN, AND ALTERED QUARTZITES ARE WHITE TO LIGHT GREEN.

SILICIFICATION AT THE BEAL DEPOSIT HAS AFFECTED MOST ROCK TYPES AND IS IN PART RELATED TO THE MINERALIZING EVENT(S). IT IS MOST APPARENT IN BRECCIA MATRICES EAST OF THE GULLY FAULT AND ADJACENT TO SILICIC VEINS THROUGHOUT THE DEPOSIT.

CHLORITE IS MOST ABUNDANT IN THE QUARTZITE MATRICES, ALONG FRACTURES AND AS ENVELOPES ADJACENT TO QUARTZ, CARBONATE AND SULFIDE VEINS. SERICITE ALSO OCCURS IN THE QUARTZITE MATRICES AND WITHIN OR ADJACENT TO QUARTZ OR QUARTZ-ADULARIA VEINS.

IRON OXIDES ASSOCIATED WITH THE MINERALIZATION INCLUDE BROWN TO TAN LIMONITE, RED HEMATITE AND YELLOWISH GREEN JAROSITE. THESE MINERALS OCCUR PRIMARILY AS FRACTURE COATINGS IN THE UPPER PORTION OF THE DEPOSIT BUT MAY EXTEND TO DEPTHS EXCEEDING 150-M (500-FT) ALONG MAJOR STRUCTURES. (HASTINGS AND HARROLD, 1988).

ALTERATION AT BEAL MOUNTAIN IS COMPLEX WITH MULTIPLE EVENTS. MAJOR EVENTS INCLUDE CONTACT METAMORPHISM, METASOMATISM, RETROGRADE ALTERATION, AND OXIDATION/WEATHERNG. INTENSITY OF ALTERATION OF EACH LITHOLOGY VARIES DUE TO ITS PROXIMITY TO INTRUSIVES, METASOMATIC REPLACEMENT, AND RETROGRADE ALTERATION. (FOR MORE DETAIL SEE FIER, 1992)
Deposit THE DEPOSIT IS LOCATED WITHIN AND ADJACENT TO A SHEAR WHICH HAS BRECCIATED AND FRACTURED THE METASEDIMENTS AND HAS PROVIDED THE POROSITY AND ENVIRONMENT NECESSARY FOR MINERAL DEPOSITION. THE MINERALIZATION IS DISSEMINATED IN THE FAVORABLE LITHOLOGIC HORIZONS AS WELL AS NARROW CROSSCUTTING VEINS. THOSE HORIZONS ARE (BEST TO WORST) THE METACONGLOMERATES, QUARTZITES, DIOPSIDE HORNFELSES AND POTASSIUM-FELDSPAR HORNFELSES. (UNPUBLISHED NOTES, MBMG MINERAL PROPERTY FILES, ROOM 213, MAIN HALL.)

Reporter information

Type Date Name Affiliation Comment
Reporter 31-MAR-98 Buckingham, David A. U.S. Bureau of Mines

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

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