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  3. Mineral Resource Data System (MRDS)

Unnamed (Francis Island)

Past Producer in Alaska, United States with commodities Silver, Gold, Copper, Zinc, Bismuth, Antimony
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Economic information about the deposit and operations
  12. Mining district
  13. Links to other databases
  14. Bibliographic references
  15. General comments
  16. Reporter information

Geologic information

Identification information

Deposit ID 10002275
MRDS ID A013179
Record type Site
Current site name Unnamed (Francis Island)
Related records 10233841

Geographic coordinates

Geographic coordinates: -136.17902, 58.62584 (WGS84)
Relative position The Francis Island mine site is on the southwest side of the island. The original site, described in several older reports (Buddington, 1926; Smith, 1933; Reed, 1938; Rossman, 1963) is now, apparently, largely covered by landslide debris. The occurrence is number 28 of MacKevett and others (1971), number 47 of Cobb (1972), and number 94 of Kimball and others (1978). It is accurate within 0.1 mile.

Site location context

Political divisions (FIPS codes)

Hoonah-Angoon(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Mount Fairweather C-1(quadrangle 1:63,360 scale)

Juneau NW(quadrangle 1:100,000 scale)

Mount Fairweather(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Glacier Bay(hydrologic unit)

Northern Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Glacier Bay National Park(National Park)

National Park NPS(Type of land area)

NPS(Federal land areas administered by NPS)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Copper Primary
Zinc Critical Primary
Bismuth Critical Secondary
Antimony Critical Secondary

Materials information

Materials Type of material
Bornite Ore
Chalcocite Ore
Chalcopyrite Ore
Magnetite Ore
Malachite Ore
Pyrite Ore
Pyrolusite Ore
Sphalerite Ore
Tetrahedrite Ore
Calcite Gangue
Tremolite Gangue

Alteration

  • (Local) Marble locally contains tremolite, and at intrusive contacts is altered to pyroxene - garnet skarn. Chlorite and tremolite also occur in calc-hornfels.

Mineral occurrence model information

Model code 59
USGS model code 18b
Deposit model name Skarn Cu
Mark3 model number 8

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Metasedimentary Rock > Marble

Nearby scientific data

(1) -136.17902, 58.62584
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The Francis Island occurrence is on the easternmost contact of a granitic intrusion of Cretaceous age. The intrusion is mostly underwater, but a substantial granitic mass, inferred to be part of the same pluton, is exposed on the south part of Marble Mountain across Whidbey Passage from Francis Island. The granitic rock is intruded into marble of Devonian and Silurian age (Brew and others, 1978; pl. IA).? Mineral deposits occur in sheared tremolitic marble and in pyroxene-garnet tactite about 5-feet thick at the granitic (quartz diorite) contact. Small rich pods of bornite and other minerals in tactite were described in older reports, including Buddington, (1926, p. 56), Buddington and Chapin (1929, p. 323), Smith, (1933, p. 323), Reed (1938, p.69) and Rossman (1963-B 1121-K, p. K51). Some of the material was mined. This site has apparently been covered by landslide debris. A mineralized fault zone 10 feet thick can be followed for 50 feet before it is covered with surficial debris; MacKevett and others (1971, fig. 8) show the probable relation of the original site to the fault zone, which locally contains chalcopyrite, bornite, tetrahedrite (?), chalcocite (?), pyrite, and probably sphalerite. Malachite and pyrolusite occur as secondary minerals. MacKevett and others (1971) reported 7000 ppm copper, 1000 ppm zinc, 200 ppm antimony, 150 ppm bismuth, 20 ppm tin, and 1.46 ounce per ton silver in a selected sample of copper-stained metamorphic rock collected at or near the fault zone. Magnetite occurs locally in the tactite. A soil survey suggests the possibility of buried mineral deposits in the area (MacKevett and others, 1971, fig. 8). ? the U.S. Bureau of Mines (Kimball and others, 1978) reported a trace of tungsten and 7 ppm silver in float samples from the area.
  • Age = Cretaceous .

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Juneau

Comments on the production information

  • Production Notes = Possible small production, no records.

Comments on the workings information

  • Workings / Exploration = Surface cuts, now concealed by landslide debris, probably date back to 2 claims staked on the island in 1923, as reported by Buddington (1926) and repeated by Smith (1933) and Reed (1938). Buddington reported gold-silver-bearing bornite in a rich sulfide pocket in the tactite. MacKevett and others (1971) obtained maximum values of 7000 ppm copper, 1000 ppm zinc, 200 ppm antimony, 150 ppm bismuth, and 1.46 ounce/ton silver in a selected sample of copper-stained rock found near the inferred buried site.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = MacKevett and others, 1971

General comments

Subject category Comment text
Deposit Model Name = Copper skarn or tactite (Cox and Singer, 1986; model 18b).
Deposit Other Comments = the deposit size is limited by the size of the island. A tactite or skarn affiliation is consisted by the high bismuth content found by MacKevett and others(1971). ? the site is in Glacier Bay National Park and Preserve.

Reporter information

Type Date Name Affiliation Comment
Reporter 14-APR-99 Hawley, C.C. Hawley Resource Group

Beyond USGS

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

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.