The Opal is a gold mine located in Alaska.
About the MRDS Data:
All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.
Mine Info
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Opal MRDS details
Site Name
Primary: Opal
Commodity
Primary: Gold
Location
State: Alaska
District: Willow Creek
Land Status
Not available
Holdings
Not available
Workings
Not available
Ownership
Not available
Production
Not available
Deposit
Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:
Physiography
Not available
Mineral Deposit Model
Model Name: Low-sulfide Au-quartz vein
Orebody
Not available
Structure
Not available
Alterations
Alteration Type: L
Alteration Text: Wall-rock alteration within a few inches of the veins is intense, but seldom extends more than 10 to 12 inches beyond the quartz filling. Sericitization and carbonate alteration predominate, but there is some pyritization and in the outer parts of the alteration zone chloritization is present (Ray, 1954).
Rocks
Not available
Analytical Data
Not available
Materials
Ore: Gold
Ore: Pyrite
Gangue: Quartz
Comments
Comment (Workings): Workings / Exploration = Tunnels started in 1919. The prospect was explored by surface excavations and about 300 ft of underground workings as of 1923 (Brooks, 1925).
Comment (Deposit): Model Name = Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Comment (Exploration): Status = Inactive
Comment (Geology): Age = Late Cretaceous or younger; veins cut the Late Cretaceous Willow Creek Pluton.
Comment (Production): Production Notes = No record of production.
Comment (Reference): Primary Reference = Chapin, 1921
Comment (Geology): Geologic Description = Two parallel veins have been traced in the quartz diorite country rock of the Late Cretaceous Willow Creek Pluton. The veins strike N 50 E, and dip 50 NW. The upper vein is 3 to 4 ft wide and consists of quartz and gouge in altered quartz diorite. The lower vein is 3 to 5 ft wide and consists of quartz stringers and gouge in altered quartz diorite. Both veins carry pyrite and free gold, and reportedly are cut by faults (Chapin, 1921).? the Willow Creek Pluton is a zoned pluton: the outer part consists of hornblende quartz diorite and lesser hornblende tonalite; the core consists of hornblende-biotite granodiorite, and lesser hornblende-biotite quartz monzodiorite and biotite quartz monzonite. Wall-rock alteration within a few inches of the veins is intense, but seldom extends more than 10 to 12 inches beyond the quartz filling. Sericitization and carbonate alteration predominate, but there is some pyritization and in the outer parts of the alteration zone chloritization is present (Ray, 1954).
References
Reference (Deposit): Chapin, Theodore, 1921, Lode developments in the Willow Creek district: U.S. Geological Survey Bulletin 714-E, p. 201-206.
Reference (Deposit): Brooks, A.H. and Capps, S.R., 1924, Mineral industry in Alaska, 1922: U.S. Geological Survey Bulletin 755, p. 1-56.
Reference (Deposit): MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous mineral deposits in the western part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-F, 38 p., 1 sheet, scale 1:1,000,000.
Reference (Deposit): Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials in the Anchorage quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-1095, 184 p.
Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Anchorage quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-409, 1 sheet, scale 1:250,000.
Reference (Deposit): MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected non-metalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000.
Reference (Deposit): Brooks, A.H., 1925, Alaska's mineral resources and production, 1923: U.S. Geological Survey Bulletin 773, p. 3-52.
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