By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Gold production from Lassen County has come mainly from the Diamond Mountain and Hayden Hill districts.
Production for 1880-1959 was 107,200 ounces. There probably was considerable production, especially from placers, before 1880, but no systematic records of this have been found.
DIAMOND MOUNTAIN DISTRICT
The Diamond Mountain district is 6 miles south of Susanville in T. 29 N., Rs. 11 and 12 E.
In the early days, most of the production was from placers; later it was almost entirely from lodes. The total recorded gold production through 1959 was 21,800 ounces, of which at least 9,700 ounces came from placers.
The district is underlain by intrusive rocks of Mesozoic age that are overlain by Tertiary gravels, lava, and alluvium (Averill and Erwin, 1936, p. 409-422). The intrusive rocks consist of biotite-quartz diorite, hornblende-quartz diorite, and granite. Overlying the gravels and capping some of the mountains are andesite lavas of Pliocene age.
The lode deposits are gold-quartz veins that occur in all three types of the igneous rocks, but the most productive deposits are in the biotite-quartz diorite. The Tertiary gravels are auriferous and have been mined locally.
HAYDEN HILL DISTRICT
The Hayden Hill district is in north-central Lassen County, in Tps. 36 and 37 N., Rs. 10 and 11 E. Estimated production for 1880-1959, utilizing estimates of Hill (1915, p. 32), was about 116,000 ounces, and all may be attributed to the lode mines, because there is no record of any placer production.
Gold was discovered in this district in 1870; in 1873 it produced $40,000 in gold. The periods 1880-84 and 1904-9 were the most productive. In 1910 most of the town of Hayden Hill was destroyed by fire (Hill, 1915, p. 30-31), and the district remained almost inactive through 1959.
The geology of this district was described by Hill (1915, p. 30-38), and the following is from his report. The country rock in the Hayden Hill district is rhyolite tuff of Tertiary age. This is cut by two sets of gold-bearing quartz veins of late Tertiary age; one trends N. 68° W., the other N. 38° E. Unconsolidated fault breccia fills many of the veins. Gold, accompanied by pyrolusite, occurs with fine sandy material in the veins.