Greenstone Creek; Greenstone Gulch Mine, Ruby Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Greenstone Creek; Greenstone Gulch Mine	Mine
Ruby Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: Greenstone Creek is a southwest-flowing tributary of Long Creek, and is about 4 miles long. Coordinates given correspond to location 23 of Cobb (1972 [MF405]) and mark the center of placer tailings 3 1/2 miles from the mouth of the creek, in section 4, T. 14 S., R. 17 E. of the Kateel River meridian, below the mouth of Greenstone Gulch. Greenstone Gulch refers to a southwesterly-flowing headwater tributary of Greenstone Creek. Tailings connect the two creeks and similar to Cobb (1972 [MF405]), this report treats both locations as one mine. The location is accurate.
Geology: The bedrock under Greenstone Creek is mostly weathered greenstone, although the headwaters are underlain by granite (Eberlein and others, 1977; Mertie, 1936). Gold was first discovered during the winter of 1912-13 (Eakin, 1914 [B592]). The gravels were 3 to 12 feet deep and worked by open-cut methods (Brooks, 1915) during 1913-14. A dredge was installed in 1915 and operational in 1916 (Smith, 1917 [BMB153]). Chapman and others (1963) reported that the gold from Greenstone Creek is generally fine and angular, spottily distributed, and occurs on bedrock. Some of the gold is described as round and associated with only a little black sand, mostly magnetite and ilmenite, although cassiterite is also present (Chapin, 1919; Chapman and others, 1963). The pay streak was 60 to 100 feet wide, and was dredged for 2 miles below the mouth of Greenstone Gulch in 1916-17. The gravel is generally less than 25 feet deep (Mertie, 1936), and a stretch of about 3 miles was eventually mined from the upper half of Greenstone Creek (Cobb, 1972 [MF405]; Jim Johnson, oral communication, 2000). Dredge production was about $500,000 in 1936 (Mertie, 1936). Nearly continuous mining occurred along the creek until 1939. From 1939 to around 1977, mining was intermittent (Eberlein and others, 1977). During the early 1980s, sonic holes and auger holes were drilled into the gravels at the lower end of Greenstone Creek, but the grade was reported to be sub-economic (Jim Johnson, oral communication, 2000). The last record of exploration along Greenstone Creek is from the Sphinx America Company in 1990 (Swainbank and others, 1991). Greenstone Creek also has a 3-mile-long tributary called Greenstone Gulch, that is unnamed on the USGS Ruby (B-6) Quadrangle map (1952, minor revisions in 1973). This area was also mined. Assays reported 865.75 parts gold per thousand and 129 parts silver per thousand (Mertie, 1936). The lower 800 feet of this creek was dredged, and other mining was conducted farther upstream (Mertie, 1936).
Workings: Beginning in 1914, the head of Greenstone Creek was stripped and mined by open-cut methods. In 1916-17, a dredge mined at least two miles of the creek (Smith, 1917 [BMB153]), and up into the lower 800 feet of Greenstone Gulch (Mertie, 1936). Mining and exploration activities along Greenstone Creek continued intermittently until at least 1990 (Swainbank and others, 1991), presumably along the approximately 3 mile stretch marked as location 23 by Cobb (1972 [MF405]).
Age: Quaternary.

Commodities (Major) - Au; (Minor) - Ag, Sn
Development Status: Yes; small
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a).

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Link to USGS - Alaska:	RB021

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References