Heaston-Oracle

Mine, Inactive

Alternative names

Alaska Oracle Mining Co.
Oracle No. 2
Oracle Extension

Commodities and mineralogy

Main commodities Au
Other commodities Cu; Mo; Pb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; gold; molybdenite; pyrite; pyrrhotite; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale SR
Quadrangle map, 1:63,360-scale C-7
Latitude 60.6208
Longitude -149.5554
Nearby scientific data Find additional scientific data near this location
Location and accuracy The mine is located in the SW1/4 section 12, T. 6 N., R. 2 W., of the Seward Meridian, at elevations between 1,800 and 2,500 feet. It is situated about a mile west of the Seward Highway along Summit Creek. This location is accurate to within 300 feet. This is location 27 of Cobb and Richter (1972), location 35 of MacKevett and Holloway (1977), location 51 of Cobb and Tysdal (1980), and location S-255 of Jansons and others (1984). The location labeled Oracle Mine on the Seward C-7 topographic map is the mill site and the location of one of the workings.

Geologic setting

Geologic description

The deposit at this mine consists of an auriferous, sulfide-bearing, quartz-carbonate vein in locally sheared graywacke and slate of the Upper Cretaceous Valdez Group of Late Cretaceous age (Tuck, 1933; Tysdal, 1978 [MF-880-A]). Tuck (1933) described the vein as striking N15E with an average dip of 60W. Where exposed in the lower workings, its width ranges from a few inches to 3 feet, averaging about 13 inches over a length of 175 feet. The ore pinches out at the north end of those workings.
The vein occupies a fault along which some movement took place before ore deposition and some of it after, as is shown by slickensides and sheared quartz (Tuck, 1933). The fault in general parallels the bedding of the graywacke and slate. Graywacke forms the footwall, and slate forms the hanging wall.
The sulfide minerals are mainly arsenopyrite, pyrite, galena, and sphalerite and total about 5 percent of the ore (Tuck, 1933). The gangue minerals are quartz and minor carbonate. Chalcopyrite, pyrrhotite, and molybdenite have also been reported. Gold occurs both free and with the sulfides.
The main workings consist of 900 feet of crosscut, 550 feet of drift, 215 feet of raise, 25 feet of winze, and considerable stoping (Hoekzema and Sherman, 1983). There are two caved portals. One is on the north side of the creek at an elevation of 1,800 feet, 200 feet west of the mill. The other is on the south side of the creek at an elevation of 1,900 feet, 1,000 feet west of the mill.
Geologic map unit (-149.557549382279, 60.6202258210796)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Cretaceous or younger; vein cuts rocks of the Valdez Group of Late Cretaceous age.
Alteration of deposit The vein is weathered to a depth of 50 to 75 feet. The quartz is friable and iron stained in this zone.

Production and reserves

Workings or exploration
The main workings consist of two levels totaling 900 feet of crosscut, 550 feet of drift, 215 feet of raise, 25 feet of winze, and considerable stoping (Hoekzema and Sherman, 1983). One portal is on the north side of the creek at an elevation of 1,800 feet, 200 feet west of the mill. The other portal is on the south side of the creek at an elevation of 1,900 feet, 1,000 feet west of the mill (Hoekzema and Sherman, 1983). Both portals were caved when the U.S. Bureau of Mines visited in 1980 (Hoekzema and Sherman, 1983).
The U.S. Bureau of Mines collected five samples. One channel sample on a vein exposed above the caved 1,900-foot-level portal assayed 1.64 ounces of gold per ton and 0.71 ounce of silver per ton. Two chip samples of wallrock assayed trace to 0.05 ounce of gold per ton and 0.01 to 0.09 ounce of silver per ton. Two grab samples from nearby dumps assayed 0.02 and 0.04 ounce of gold per ton and 0.02 and 0.04 ounce of silver per ton (Jansons and others, 1984).
Indication of production Yes; small
Production notes Total recorded production is 1,274 ounces of gold and 256 ounces of silver (Jansons and others, 1984).

Additional comments

This mine is not in the location labeled the 'Oracle mine' on the Seward C-7 topographic map.

References

MRDS Number A010346

References

Hoekzema, R.P., and Sherman, G.E., 1983, Mineral investigations in the Chugach National Forest, Alaska (Peninsula study area): U.S. Bureau of Mines in-house report; held at U.S. Bureau of Land Management Alaska State Office, Anchorage, 524 p.
Reporters Jeff A. Huber (Anchorage)
Last report date 5/1/2000