Champion Mine area, located in the Rochester mining district of the Humboldt Mountains, Pershing County, Nevada.
|Dumortierite-sericite schist, composed mostly of dumortierite, sericite (AKA fine-grained muscovite), quartz, and possibly andalusite.|
|Sheen from the fine-grained, clear to white sericite (muscovite) on foliation planes and disseminated in the schist.|
|Lavender dumortierite schist.|
Dumortierite has been mined for use in making refractory ceramics such as those used in spark plugs. It is sometimes used as a gemstone (or rock), and the blue varieties have sometimes been used to make fake lapis lazuli.
By the way, these rocks are currently unlabeled. Andrew Alden has a good post up recommending that everyone label their rocks and minerals (with name and location or provenance). I will be able to label precisely all but the reddish volcanic rock.
Friday Photo: Dumortierite
The Road to the Champion Mine
Rock Walls at the Champion Mine Lower Workings
Dumortierite at the Champion Mine, Nevada
Upper Champion Mine Workings
Mackay School of Mines staff, 1928, A bulletin by the Mackay School of Mines staff on the mineral dumortierite, University of Nevada Bulletin, vol. 22, no. 2: Nevada Bureau of Mines and Geology Bulletin 8, 47 p., including 1 oversized page.