By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Lane County has been a relatively small gold producer even though mining of the precious metals began as early as 1858 and continued in a desultory fashion through the 1940's. Most of the gold has come from veins in the Bohemia and Blue River districts.
Total recorded gold production of Lane County from 1880 through 1959 was slightly more than 46,000 ounces. Considering that mining began in 1858, it seems reasonable to assume that at least 50,000 ounces of gold was produced. The rocks exposed in the county are sedimentary and igneous and range in age from Eocene to Recent (Smith and Ruff, 1938, p. 11-22).
The oldest rocks are sandstones, shales, and volcanics composing the Umpqua Formation of Eocene age. This is overlain by the Calapooya Formation, also of Eocene age, consisting dominantly of pyroclastics. The uppermost Eocene formation is the Tyee Sandstone. Oligocene sediments are the Fisher Formation (tuffs and breccias) and the Eugene Formation (tuffaceous sandstone and shale). The Eocene and Oligocene sediments are present in the western half of the county, generally west of the Willamette River valley.
A thick section of Miocene, Pliocene, and Pleistocene basalt and andesite lava flows, associated tuffs and agglomerates, and some dioritic intrusives younger than the Miocene lavas compose most of the bedrock of the eastern part of the county, including the Cascade Range. Some of the volcanic activity extended into Pleistocene and Recent time.
The gold deposits are in oxidized-sulfide veins of Eocene or younger age.
BLUE RIVER DISTRICT
The Blue River district is in Lane and Linn Counties, between lat 44° 10' and 44°20' N. and long 122°10' and 122°25' W.
The Lucky Boy mine, the only large producer in the district, was discovered in 1887. Gold production from the district was estimated to be worth $50,000 to $100,000 before 1896, and it was 7,728 ounces from 1896 to 1924 (Callaghan and Buddington, 1938, p. 115-116). Only 44 ounces was reported from the district from 1924 through 1959. The total production, using the lower estimate of Callaghan and Buddington, was about 10,200 ounces.
The geology of the district, as described by Callaghan and Buddington (1938, p. 114-117), is characterized by flat-lying andesitic lavas and breccias of probable Miocene age which have been intruded by small plugs and dikes of diorite. The ore deposits are in small quartz veins containing sphalerite, galena, chalcopyrite, pyrite, and local tetrahedrite. Apparently most of the ore bodies are in the oxidized parts of these veins.
The Bohemia district is 35 miles southeast of Cottage Grove between lat 43°35' and 43°45' N. and long 122°35' and 122°45' W. on the divide between the Umpqua and Willamette drainage systems.
The district was described by Callaghan and Buddington (1938, p. 38-81), and the information that follows, unless otherwise noted, was abstracted from their report.
The district was discovered in 1858, and some ore was mined until 1877, when the mill closed and the district became inactive (Diller, 1900, p. 7). In 1891 there was a revival of activity that continued until about 1912. Since then, activity has been somewhat sporadic. There was no recorded production from 1952 through 1959.
The entire gold production of 14,591 ounces in Lane County from 1880 to 1900 is credited to the Bohemia district. From 1902 through 1930 the district produced 13,695 ounces, and from 1931 through 1959 it produced 10,270 ounces of lode gold and 81 ounces of placer gold. Total recorded gold production through 1959 from the district is 38,637 ounces.
Most of the district is underlain by bedded Miocene (?) volcanic rocks with an aggregate thickness of 6,500 feet. These rocks are composed of approximately equal amounts of tuffs, andesite lavas, and volcanic breccias. Several small dioritic plugs, dikes, and a stock intrude the volcanics, and the gold deposits seem to be arranged around the intrusives. The deposits are oxidized sulfide veins containing in the unweathered state drusy quartz, galena, chalcopyrite, sphalerite, and specularite.