Boulder County Colorado Gold Production
The Ward district is in western Boulder County, west of the Gold Hill-Sugarloaf district and about 9 to 13 miles northwest of Boulder. It comprises 12 square miles in the headwaters of Lefthand and Fourmile Creeks and includes the mining camps of Sunset and Copper Rock.
Gold was first discovered in 1861, and by 1870 most of the major lodes had been located. The Niwot and Columbia mines were the largest gold producers; however, Worcester (1920, p. 56) noted that there were more than 50 mines in the district that had produced more than $5,000 worth of ore. Gold mining in the district declined after 1893; it revived briefly during 1936-42, but it waned from 1943 through 1959. The exhaustion of the rich oxidized ores left only low-grade sulfide ores that have thus far resisted all attempts at successful treatment.
The early gold output of the Ward district can only be estimated. Using Henderson's (1926, p. 106) figure of $15,954,999 for Boulder County from 1859 to 1923 and Worcester's (1920, p. 70) assumption that Ward produced 20 to 24 percent of the total dollar value of Boulder County mineral production through 1915, we can credit the district with a minimum of $3,191,000 or about 154,400 ounces of gold through 1923. Total gold produced through 1959 was roughly 172,000 ounces, mostly from quartz veins. The small placer deposits were exhausted long ago.
The country rock in the Ward district is largely Precambrian in age. Gneiss and schist of the Idaho Springs Formation predominate in the southern part of the district, whereas Silver Plume Granite is the major bedrock in the northern part. Several stocks of diorite and monzonite porphyry and smaller masses of sodic andesite and diorite porphyry and a wide variety of dikes of Tertiary age intrude the Precambrian rocks throughout the district (Lovering and Goddard, 1950, p. 203).
Nearly all the ore in the Ward district occurs in veins or in shoots or chimneys that appear to be local enlargements of veins. Most of the productive veins are in the granite or granite gneiss; many veins feather out in the schist. The veins either follow or are closely associated with felsite, dacite, quartz monzonite, latite, or quartz latite dikes. Gold, silver, and lead have been mined in appreciable quantities; and copper, zinc, and tungsten have been produced in small amounts. Most of the gold has been derived from quartz veins rich in chalcopyrite; lesser amounts have come from quartz-pyrite veins with minor molybdenite and wolframite. Native gold and gold alloyed with silver occur in small amounts in ores that contain sphalerite and argentiferous galena as the chief constituents. Gold telluride ores are found in mines in the eastern part of the district (Lovering and Goddard, 1950, p. 203-207).