By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Okanogan County, one of the largest counties in the State, has several gold-producing districts - Cascade, Oroville-Nighthawk, Myers Creek, and Methow.
Mining in the county began in 1859 in the gravels along the Similkameen River. In 1871, lode deposits were discovered near Conconully (Patty, 1921, p. 20). Production data on gold before 1903 are not available, but from that date through 1959 the county produced 34,000 ounces of lode gold and 1,775 ounces of placer gold. Total gold production for the county from 1859 through 1959 was probably between 85,000 and 90,000 ounces.
Metamorphic rocks and local patches of sedimentary rocks compose the bedrock of the county. These have been extensively intruded by granite and other igneous rocks.
The Cascade (Wauconda) district, near the east boundary of Okanogan County, is about 20 miles south of the Canadian boundary and 12 miles northwest of Republic, at the headwaters of Granite Creek.
Production data for the district are available only for 1935 to 1957, when 7,886 ounces of lode gold was produced, primarily from the Bodie mine. Although the discovery date of gold for the district is not known, activity was reported as early as 1901 (Landes and others, 1902, p. 25). It can be assumed that in the ensuing 34 years at least a few thousand ounces of gold was produced and that an estimated total production of 10,000 to 15,000 ounces is reasonable. The principal properties are the Wauconda (Landes and others, 1902, p. 25-26) and the Bodie (Huntting, 1955, p. 69).
The bedrock of the district consists of gneiss, schist, and metasedimentary rocks that have been intruded by masses of granite (Landes and others, 1902, p. 24). These rocks are cut by porphyritic andesite intrusives and are covered by basaltic lavas. The ore bodies are in fissure veins in the metamorphic rocks. The vein material is largely quartz and calcite, and finely divided native gold is the ore mineral.
The Methow (Squaw Creek) district is along Squaw Creek - a tributary of the Methow River - and is 9 miles above the mouth of the Methow River, 53 miles north of Mansfield, and 73 miles north-northeast of Wenatchee.
Lode deposits were discovered in 1887; the Red Shirt mine was the first producer (Hodges, 1897, p. 85). The major properties are the Hidden Treasure, Friday, Bolinger, and Highland Light. Production data before 1932 are incomplete, but from 1932 through 1959 output of 16,473 ounces of lode gold and 9 ounces of placer gold is recorded.
The deposits are in east-trending fissure veins in gneiss and granite. Quartz and calcite compose the bulk of the veinfilling, and gold and silver are the valuable components (Landes and others, 1902, p. 37).
MYERS CREEK DISTRICT
The Myers Creek (Chewsaw, Mary Ann Creek) district is in the northeast corner of Okanogan County near the town of Chewsaw.
Placer gold was discovered in this district in 1888 along Mary Ann Creek (Landes and others, 1902, p. 27), but the area was not developed to any extent until the early 1900's. Most of the production was from lode deposits. Including estimates by Umpleby (1911a, p. 28), the total gold production of the district through 1959 was a minimum of about 9,500 ounces.
The area is underlain by a thick series of Paleozoic sedimentary rocks, lava, and porphyry that were intruded by granitic masses of Mesozoic age (Umpleby, 1911a, p. 29-32). The Paleozoic igneous rocks are andesite and basalt; the Mesozoic batholithic masses are syenites and granites. Quartzite is the most abundant rock in the sedimentary section ; however, slate, schist, and limestone are also present.
Copper, gold, and silver ore deposits are of two types - contact metamorphic replacement deposits in limestone near the contact of the intrusives and invaded rock, and fissure veins (Umpleby, 1911a, p. 32-39). In the replacement deposits chalcopyrite is the chief ore mineral; gold is a subordinate constituent in the chalcopyrite and pyrite. In the fissure veins, which occur in all rock types in the district, free gold, chalcopyrite, pyrite, galena, sphalerite, and arsenopyrite are found in a gangue of quartz and calcite. Gold is more abundant in the vein deposits.
The Oroville-Nighthawk (Palmer Mountain) district, in northern Okanogan County, is just south of the international boundary between lat 48°50' and 49°00' N. and long 119°28' and 119°42' W.
As early as 1859 placers were worked on the Similkameen River (Umpleby, 1911b, p. 75-76), but this activity ended when the area was set aside as an Indian reservation. The district was reopened in the late 1890's, at which time lode deposits were developed. Most of the production was before 1900. Umpleby (1911b, p. 76) estimated a maximum out put before 1900 of $1 million in gold - half placer and half lode.
Data from 1903 through 1959 show a total output of 450 ounces of placer gold and 740 ounces of lode gold. Total production from the district through 1959 may be estimated as 49,000 to 50,000 ounces - half placer gold and half lode gold.
The oldest rocks in the area are clay slate, siliceous schist, limestone, and interbedded andesite and basalt believed to be of Paleozoic, possibly Carboniferous, age. The Similkameen batholith, a granitic mass of Late Cretaceous or early Tertiary age, intruded the metasedimentary rocks. Tertiary lake beds, locally deformed, cover considerable areas near the Similkameen River; these lake beds are unconformably overlain by scattered patches of andesite flows (Umpleby, 1911b, p. 64-84; Patty, 1921, p. 222-228).
Ore deposits are of two types: disseminated deposits rich in copper, and vein deposits carrying considerable gold, silver, lead, and copper. The disseminated deposits are related to the Similkameen batholith (Patty, 1921, p. 224), and the veins are distributed along the granite-sedimentary rock contact. Veins show varied mineralogy; they range from simple quartz veins to others showing successive movement and overlapping deposition of sulfides.
Gold, which is the chief commodity in some veins, occurs as native gold and also in pyrite, chalcopyrite, and galena. Silver occurs in various silver minerals, argentiferous galena, and cerargyrite. The disseminated copper deposits have not been developed to any great extent.