Baker County Oregon Gold Production
The Rock Creek district is between lat 44°49' and 45°03' N. and long 118°00' and 118°15' W., 10-15 miles northwest of Baker.
The district, discovered in the late 1880's, was a steady gold producer until 1914, after which activity declined; it was idle in 1959. The principal mine, the Baisley-Elkhorn, produced an estimated $950,000, chiefly in gold (Oregon Department of Geology and Mineral Industries, 1939, p. 85).
Estimated early production of the district was $1 million, mostly in gold (Lindgren, 1901, p. 646). Production from 1934 through 1959 totaled 3,282 ounces of lode gold and 193 ounces of placer gold. A conservative total for the district would be about 51,000 ounces of gold.
The following is summarized from Lindgren's (1901, p. 645-647) description of the geology of the district. The north end of Elkhorn Ridge is composed of granodiorite, the south part is dominantly argillite, and the Rock Creek district is along the contact between them. Diorite dikes cut the argillite near the contact. Near its borders the intrusive is dioritic, becoming granodioritic toward the interior. Most of the veins are discontinuous but form a zone in the diorite approximately parallel to the argillite-diorite contact. Gangue is quartz with some calcite. Gold occurs in pyrite or as an intergrowth with sphalerite. Other sulfides are galena, chalcopyrite, and locally ruby silver.
SPARTA DISTRICT
The Sparta district is between lat 44°36' and 44°57' N. and long 117°02' and 117°23' W.
Although placer deposits were known in the area at an early date, it was not until 1873, when the Sparta ditch was completed, that enough water was available to exploit the gravel-filled gulches which yielded about $157,000 in gold before 1900 (Lindgren, 1901, p. 737). Quartz veins were discovered a few years after the discovery of the placers, and from 1889 to 1892 they yielded $677,000 in gold (Lindgren, 1901, p. 736). Shortly thereafter the district declined rapidly, and from 1952 through 1959 it was idle. Total production from the district through 1959 was about 35,200 ounces of lode gold and about 7,700 ounces of placer gold.
The district is underlain by quartz diorite and albite granite of presumable Mesozoic age (Gillully and others, 1933, p. 57-58). These rocks intruded Permian greenstone, only remnants of which remain in the area. Columbia River Basalt unconformably overlies the older rocks. The ore deposits are gold-bearing quartz veins in the diorite and granite. Most of the veins are narrow and cannot be followed for any great distance.