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Castle Island

Past Producer in Alaska, United States with commodities Barium-Barite, Silver, Copper, Lead, Tin
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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. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10308982
MRDS ID A010345
Record type Site
Current site name Castle Island
Related records 10000297

Geographic coordinates

Geographic coordinates: -133.16488, 56.65274 (WGS84)
Relative position Location of mine is known precisely. However, the original outcrop of the deposit was little more than a large offshore rock just off the northeast end of 'Castle Island'; that original outcrop has now been completely mined out to below sea level. Note that what is almost universally called Castle Island, i.e. the site of the barite mine, is not identified as such on the USGS 1:63,360-scale topographic map and none of the Castle Islands is specifically labeled as Castle Island on the current (1998) maps. The island that is the site of the mine and is described here is an islet about about 650 yards long located about 1,500 ft south-southeast of the Big Castle Island labeled on current topographic maps. Localities 31 and 32 of Grybeck, Berg, and Karl (1984).

Site location context

Political divisions (FIPS codes)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Petersburg C-4 NE(quadrangle 1:24,000 scale)

Petersburg N(quadrangle 1:100,000 scale)

Petersburg(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Central Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Barium-Barite Critical Primary
Silver Secondary
Copper Secondary
Lead Secondary
Tin Critical Secondary

Comments on the commodity information

  • Gangue = Common rock-forming minerals interlayered with the barite.

Materials information

Materials Type of material
Barite Ore
Bornite Ore
Chalcopyrite Ore
Galena Ore
Pyrite Ore
Pyrrhotite Ore
Sphalerite Ore
Tetrahedrite Ore

Alteration

  • None obvious.

Mineral occurrence model information

Model code 184
USGS model code 28a
Deposit model name Massive sulfide, kuroko
Mark3 model number 93

Nearby scientific data

(1) -133.16488, 56.65274
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The ore body consisted of a Lenticular, massive barite lens about 300 feet long and up to 200 feet thick that extended to a maximum depth of about 150 feet below sea level. The exact stratigraphic relations are unclear because most of the deposit was under salt water. However, examination of unpublished drilling data and cross sections maintained by the mine indicates that the barite lens probably occurred along the trough of a symmetrical open syncline trending about N70W with limbs dipping about 30 to 45 degrees Drilling also indicated a considerable tonnage of lower grade barite interbedded with 'gray schist,' 'chert,' and 'graphitic schists,' and the possibility of at least one more high-grade barite lens offshore. Mine-run material was massive, white to light gray, almost pure barite that almost invariably contained a percent or so of sulfides as tiny disseminated grains. Assays of the massive barite indicate that it typically contains about 0.5-2% Zn, about 0.5% Pb, a small amount of Cu, and about 1 ounce Ag per ton. Under the reflecting microscope, the sulfides are seen to be sphalerite, galena, pyrite, pyrrhotite, bornite, tetrahedrite-tennantite, and chalcopyrite, together with minor amounts of other ore minerals, all as tiny, generally equant grains. Examination of waste dumps provide many samples that show all transitions from massive barite to layered pyrite (-sphalerite -quartz)-barite rock with the other sulfides noted previously disseminated though the rock in minor amount. The association of barite, layered sulfide-barite rocks, schistose metafelsite(?), and black carbonaceous, calcareous phyllite at the mine site indicate that it is part of the Triassic Duncan Canal-Zarembo Canal belt of dismembered, volcanogenic massive-sulfide deposits described by Berg and Grybeck (1980) and Berg (1981). This description is synthesized from Burchard (1914); Buddington (1923); Buddington (1925); unpublished written and oral data from David Carnes, U. S. Bureau of Mines; unpublished field notes by the reporters; and analyses summarized in Grybeck, Berg, and Karl (1984). The Castle Islands largely -- and the island on which the barite mine occurs specifically -- consist largely of Upper Triassic Hyd Group rocks which are dominantly felsic and intermediate volcanic flows and breccia, limestone and argillite. However, parts of the islands also consist of Devonian limestone and Quaternary basalt whose relationship to the Hyd Group rocks is probably structurally complicated and largely hidden under water (Brew, 1997 [OF 97-156-J]).
  • Age = Probably Late Triassic.

Economic information about the deposit and operations

Development status Past Producer
Commodity type Non-metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Kupreanof

Comments on the production information

  • Production Notes = Exact production not systematically reported but total production was about three-quarters of a million tons of barite, most of which was mined from 1968 to 1973 as direct shipping ore. Swainbank and others (1995) indicate total production was 776,390 tonnes (865,000 tons) of raw and refined barite produced from 1963 to 1980.

Comments on the reserve resource information

  • Reserves = Economic reserves were exhausted by 1980 and the mining plant was then removed. There is potential for lower grade or deeper extensions of the ore body underwater but it is doubtful they can be economically mined with current (1998) technology and economics (oral and written communication with David Carnes, U. S. Bureau of Mines, who was the mining engineer in charge of the mine over most of its life).

Comments on the workings information

  • Workings / Exploration = Deposit known since before World War I. Mined from 1965 to 1980 for barite; the mine was closed and all mining equipment was removed from the property in 1981. The original deposit was originally a small outcrop at the northeast end of the island that was entirely removed by mining. Much of the mining was from an offshore barge that used a dragline to recover ore fragmented by submarine blasting. Essentially, the mine was operated as a submarine open pit from a camp on the island. An earlier phase of drilling and sampling on the original barite outcrop that ultimately resulted in mining the deposit was documented by Race (1963 [PE 117-9]) and Williams and Decker (1932 [IR 117-1]). At least 22 claims were staked in the vicinity on the surrounding islands and were active from before, probably long before, 1954 to at least 1975.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Grybeck, Berg, and Karl (1984); this description

General comments

Subject category Comment text
Deposit Model Name = Barite facies of a Kuroko massive-sulfide model (Cox and Singer, 1986; model 28a); alternatively a barite facies of a Sierran Kuroko model (Bliss, 1992; model 28a1)
Deposit Other Comments = Visited briefly by D. Grybeck, USGS, in July, 1996; no sign of mining activity since 1980 or of recent surface exploration. All the mining equipment has been removed from the island and it is now largely covered by alder and brush.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-NOV-1998 H.C. Berg and D.J. Grybeck U.S. Geological Survey

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.