Amethyst

Prospect, Inactive

Alternative names

Unga

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; Cu; Hg; Pb; Zn
Ore minerals chalcopyrite; galena; gold; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale PM
Quadrangle map, 1:63,360-scale A-2
Latitude 55.188
Longitude -160.654
Nearby scientific data Find additional scientific data near this location
Location and accuracy The map site of the Amethyst prospect is at an elevation of 500 feet, 500 feet northwest of the center of sec 3, T. 58 S., R. 75 W., Seward Meridian. The location is accurate to within 1,200 feet.

Geologic setting

Geologic description

The northeast-striking Amethyst vein at its westernmost end is located approximately 200 feet south of the Altair vein (PM091); however, it has a more northerly strike, and farther to the northeast it intersects both the Altair (PM091) and the Ankle Creek (PM090) veins (Peterson and others, 1982, figure 11). The Amethyst vein has been traced for approximately 2,000 feet on strike. The vein is a braided system, generally 15 to 20 feet in width, composed of numerous quartz veins of varying widths. Individual veins in the system branch, interweave, pinch, and swell (Trujillo and others, 1982). It exhibits evidence of crushing, brecciation, and partial rehealing. Vein quartz generally makes up 20 to 50 percent of the system. Sulfide minerals include pyrite, chalcopyrite, galena, and sphalerite. The host rocks are propylitized and argillized, pyritic andesite flows and tuffs of the late Eocene to early Oligocene Popof volcanic rocks (Wilson and others, 1995).
An ore shoot at the intersection of the Amethyst and Ankle Creek veins has been drilled and trenched It is approximately 300 feet long, 12 feet wide, and extends to a depth of 100 feet. Ore intercepts of three core holes include 16.3 feet grading 0.20 ounce of gold and 0.6 ounce of silver per ton, 31 feet grading 0.20 ounce of gold and 0.4 ounce of silver per ton, and 10 feet grading 0.08 ounce of gold and 0.6 ounce of silver per ton (Anderson and others, 1980). The assays also show up to 1,120 ppm copper, 2,300 ppm lead, 670 ppm zinc, 1,100 ppm arsenic, and 0.64 ppm mercury. Trench samples include 12 feet grading 0.105 ounce of gold and 0.17 ounce of silver per ton, 12 feet grading 0.242 ounce of gold and 0.68 ounce of silver per ton, and 12 feet grading 0.335 ounce of gold and 1.56 ounces of silver per ton (Trujillo and others, 1981). The resource is estimated to be 30,000 tons of ore grading 0.23 ounce of gold and 0.8 ounce of silver per ton.
Other trenches and drill holes along the system indicate anomalous, but not sub-ore-grade precious metal values.
Geologic map unit (-160.656067795478, 55.1871636024926)
Mineral deposit model Epithermal gold vein
Age of mineralization Eocene or younger.
Alteration of deposit The host rocks exhibit weak to strong propylitic and argillic alteration. The propylitic alteration is accompanied by 2 to 5 percent disseminated pyrite.

Production and reserves

Workings or exploration
During the period 1980 to 1982 Resource Associates of Alaska and UNC Teton Exploration Drilling Company mapped and sampled the prospect conducted VLF-EM, IP, and magnetometer surveys, core drilled 11 holes for a total of 4,446 feet, and cut 11 trenches. One ore shoot was outlined and evaluated at 30,000 tons grading 0.23 ounce of gold and 0.8 ounce of silver per ton (Trujillo and others, 1981).
In 1986 Battle Mountain Exploration Company carried out orientation soil, magnetometer, and VLF surveys over the prospect.
Redstar Gold Corp. conducted two phases of exploration in 2016 on their Unga project, which includes the Shumagin (PM064), Apollo (PM079; PM084), Centennial, Orange Mountain (PM067), Zachary Bay (PM054), Amethyst (PM092), and Aquila (PM086) epithermal gold-silver prospects. The Shumagin trend parallels the historically mined Apollo–Sitka vein system (PM079; PM084; PM076), which between 1886 and 1922 produced approximately 150,000 ounces of gold at a grade of approximately 0.292 ounce of gold per ton (Athey and Werdon, 2017).
In June 2016, Redstar Gold Corp.’s Phase I surface program included classifying alteration assemblages and conducting other geologic work to identify drill targets. From October through November, Phase II’s drilling program tested the down-dip and along-strike expansion potential of high-grade vein/breccia mineralization within the Shumigan Gold Zone (PM064). A total of 1,505 meters were drilled in 7 holes spaced over ~750 meters of strike length. All drill holes intersected the target structure, which includes multi-generational phreatomagmatic breccias, hydrothermal breccias, and late breccias and veins with colloform-crustiform- to cockade-textured quartz-adularia-carbonate (± rhodochrosite, ± green clay). Select intervals from drill holes 16SH019 and 16SH020 include 0.9 meter at 14.95 grams of gold per tonne and 1.15 meters at 11.3 grams of gold per tonne; release of full assay results is planned for late January 2017 (Athey and Werdon, 2017).
Indication of production None
Reserve estimates An ore shoot on the prospect contains an estimated 30,000 tons grading 0.23 ounce of gold and 0.8 ounce of silver per ton.

Additional comments

This prospect is located on land patented by, or interim-conveyed to, the Aleut Corporation.

References

References

Andersen, G.D., Butherus, D.L., Fankhauser, R.E., Pray, J.C., Lindberg, P.A., and Hoffman, B.L., 1980, Exploration and evaluation of lands leased from Aleut Native Corporation 1980: Resource Associates of Alaska Report, 84 p, 16 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Peterson, R.J., Lemmers, J., Handverger, P., Gallagher, J., Pilcher, R., East, J., Macleod, T., Bartels. E., 1982, Geology and precious metals potential Unga, Popof, and Korovin Islands, Shumagin Group, Aleutian Chain, Alaska: UNC Teton Exploration Drilling Company report, 127 p., 5 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Trujillo, R.S., Andersen, G.D., MacLeod, T., Hendrick, K., Farnham, S., Peterson, J., 1981. Exploration and evaluation of the Unga-Popof-Korovan Islands portion of lands leased from Aleut Native Corporation: Resource Associates of Alaska report, 70 p., 38 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
Reporters S.H. Pilcher; M.B. Werdon (DGGS)
Last report date 8/26/2017