Diamond
Unknown diamond occurrence [1], Volcano, Volcano Mining District, Amador County, California, USA
ILL. No. 7. Diamond, natural crystal, found at Volcano, Amador County
Kunz, George F. (1905) Bulletin (37), Gems, Jewelers' Materials, and Ornamental Stones of California (2nd ed.) California State Mining Bureau, p.40-41
Amador County.—...in a compact volcanic ash or tufa, forming a gray “cement-gravel.” At Volcano the rock is ...