CHELAN LAKE DISTRICT
The Chelan Lake (Holden, Railroad Creek) district is in northwest Chelan County on the east slope of the Cascade Range between lat 48Â°07' and 48Â° 19' N. and long 120Â°30' and 120Â°45' W. Chelan Lake forms the northeast boundary of the district.
Activity in this area began at least as early as 1892, when first claims were staked by J. H. Holden. Other prospects were located in the 1890's; among these was the Crown Point mine which began producing molybdenum ore in 1897. Little else of the early history of the district was recorded. In 1938, after years of options and changes of owners, the Holden mine was taken over by a subsidiary of the Howe Sound Co. It then became the largest gold, silver, and copper producer in the State, and remained so until 1956, when increased costs and complex mining problems made operation marginal. The mine was closed in 1957.
Production of the district (in large part, that of the Holden mine) from 1938 through 1951 was 514,525 ounces of gold. Its production data from 1952 through 1956 were combined with data of other districts and could not be determined separately.
The country rock in the vicinity of the Holden mine consists of hornblende and biotite-bearing schist and gneiss, quartzite, and marble of probable pre-Devonian age (F. W. Cater, oral commun., 1962). These rocks were isoclinally folded and sheared, then were intruded by peridotite and quartz-ornblende diorite bodies, and later, by dikes, sills, and small offshoots of the Cretaceous Chelan batholith, which is well exposed east of the district. Plugs and dikes of the Cloudy Pass granogabbro, of Tertiary age, intrude the older rocks. The ore deposits are replacements of a breccia zone in the metamorphic rocks. The ores are Tertiary in age and are related to the Cloudy Pass intrusive. Prominent ore minerals are magnetite, quartz, pyrite, pyrrhotite, sphalerite, and chalcopyrite, and galena and gold occur in minor amounts.
The Entiat district, in east-central Chelan County, is the largest district in the State and occupies 790 square miles between lat 47Â°40' and 48Â°00' N. and long 120Â° 10' and 120Â°45' W.
Huntting's report (1943, p. 24-26) constitutes most of the published information on the history and ore deposits of this district. The largest mine in the area is the Rex (or Rogers) mine, which produced $170,000 (about 8,250 ounces) in gold by 1930 (Huntting, 1955, p. 48). The Rex was in existence as early as 1906, so the Entiat district dates back to that time and perhaps earlier. Small platinum and gold placers along the Entiat River were worked also, but production from them was small.
The 8,250 ounces of gold produced from the Rex mine between 1906 and 1930 is the only recorded production from the Entiat district. Huntting (1943, p. 25), however, listed two other lode mines that produced unknown amounts. Estimated minimum total production for the Entiat district is 10,000 ounces.
Huntting (1943, p. 24-25) summarized the geology of the district, part of which was studied in detail by Waters (1932). The oldest rock is the Swakane Gneiss, believed to be pre-Ordovician in age, which is intruded by the Chelan Granodiorite. Locally along Lake Chelan are small patches of other Paleozoic metasedimentary rocks and scattered through the area are remnants of Tertiary lake deposits and basalt.
Free gold, the chief ore mineral, occurs with quartz in veins cutting the Swakane Gneiss. Native silver, cinnabar, ilmenite, and nickel-rich pyrrhotite occur in the ores in varying amounts. The relation of ore deposits to any of the nearby intrusives has not been determined.
The Wenatchee district is in the southeastern corner of Chelan County at about lat 47Â°22' N. and long 120Â°20' W.
The Gold King mine, the chief mine of the district, was located in 1885, but very little mining was done until 1894, when about $1,600 in bullion was produced. Sporadic activity continued until 1911 and again from 1934 to 1949. When the Lovitt Mining Co. acquired the property in 1949, production began on a large scale. Lovitt and McDowall (1954, p. 38) reported a total of 102,376 ounces of gold produced from 1949 through 1953; this high output continued, and in 1960 the Gold King was the tenth largest producer of lode gold in the United States. Total gold production of the Wenatchee district through 1959 was about 190,000 ounces (A. E. Weissenborn, written commun., 1962).
Bedrock in the vicinity of the Gold King mine consists of steeply dipping beds of the Swauk Sandstone of Eocene age. The ore deposits are in a silicified dikelike body that is cut by innumerable small quartz veins. The ore minerals are gold, silver, and minor amounts of pyrite; however, there seems to be no relationship between the valuable minerals and the pyrite. The gold is very finely divided in the quartz (Lovitt and McDowall, 1954, p. 38-39).
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