| Main commodities | W |
|---|---|
| Other commodities | Be; Mo; Sb |
| Ore minerals | meliphanite; molybdenite; scheelite; stibnite |
| Quadrangle map, 1:250,000-scale | FB |
|---|---|
| Quadrangle map, 1:63,360-scale | D-1 |
| Latitude | 64.981 |
| Longitude | -147.367 |
| Nearby scientific data | Find additional scientific data near this location |
| Location and accuracy | The Stepovich mine is located in the SW1/4SW1/4 sec. 21, T. 2 N., T. 2 E., Fairbanks Meridian. The Stepovich mine is located just west of the summit of Gilmore Dome and is accessible by a road from the Steese Highway up Gilmore Creek. The prospect is included in locality 32 of Cobb (1972 [MF 410]). |
Geologic descriptionIn 1915, Johnson discovered a scheelite-bearing lode in a crystalline marble bed in schist. The marble has intervals that consist of calcite, pyroxenite, hornblende, and quartz associated with granular scheelite ore, quartz pegmatite, and silicified mica schist (Mertie, 1917; Byers, 1957). The crystalline marble is in discontinuous, irregular bodies roughly parallel to the foliation of the schist. Various descriptions indicate that the limestone may occur as an impure, thin beds, interlayered with other sedimentary rock, or as irregularly shaped, lens-like bodies of relatively pure limestone found at irregular intervals (Gebhardt, 1942). The average thickness of the marble is 2 feet, but it may be as much as 10 feet thick in troughs and crests of folds. Granular scheelite is localized at the intersections of limestone [marble] and scheelite-bearing quartz pegmatite. Typical contact-metamorphic minerals are present, including the beryllium mineral, meliphanite. Green amphibolite forms the footwall of the lode below the 50-foot level of the shaft. The lode generally strikes about N 70 W and dips about 35 NW (Byers, 1957). It is offset as much as several tens of feet along steep, northward-striking faults. The weighted average of 32 channel samples in the ore zones was 6.1 percent tungsten tri-oxide, and the average of the ore that was mined was less than 5 percent (Byers, 1957). The richest ore shoots are at the intersections of marble and pegmatite dikes (Berg and Cobb, 1967, p. 220). | |
| Geologic map unit | (-147.369438706734, 64.9805764918605) |
|---|---|
| Mineral deposit model | W skarn deposit (Cox and Singer, 1986; model 14a) |
| Mineral deposit model number | 14a |
| Alteration of deposit | Silicified layers in the marble contain pyroxene, hornblende, and quartz (Mertie, 1917). |
| Workings or exploration | During the period 1915-18, inclined shafts were driven down the dip of the lode. In 1942-44, Cleary Hill Mines Co. sank a 170-foot inclined shaft with levels at 50 feet and 150 feet. Gabhardt (1942) reported shafts 50 and 190 feet deep and about 300 feet apart and a 100-foot tunnel. By 1957, there were 2,000 feet of underground workings (Byers, 1957). |
|---|---|
| Indication of production | Yes; small |
| Production notes | From 1915 to 1916, the Tungsten claim produced 210 tons of ore. During World War I, the production was 10 tons of concentrates that contained about 65 percent tungsten tri-oxide; 300 tons of sorted ore contained 8 percent tungsten tri-oxide, but only 2 percent was recoverable. Production from 1942 to 1944 was about 98.4 tons of ore (Byers, 1957). There was as small mill on the property that recovered the scheelite concentrate on a Wilfley table. |