Deanesmithite

deanesmithite

edoylerite

cinnabar

edgarbaileyite

Images

Formula: Hg1+2Hg2+3S2O(CrO4)
Anhydrous chromate, mercury-bearing mineral
Crystal System: Triclinic
Specific gravity: 8.06 calculated for the empirical formula and 8.14 for the idealised formula
Hardness: 4½ to 5
Streak: Red, orange
Colour: Red, orange
Luminescence: Not fluorescent under either long wave or short wave UV
Environments

Hydrothermal environments

Although deanesmithite was approved in 1991, to date (February 2025) it has been reported only from the type locality.

Localities

At the type locality, the Clear Creek claim, Goat Mountain, San Benito County, California, USA, deanesmithite has been identified on two specimens collected from a small prospect pit near the long-abandoned mercury mine. It is very rare. On the discovery specimen deanesmithite is associated with anhedral crystalline masses of cinnabar and powdery coatings of cinnabar on a rock principally composed of quartz and magnesite. Edgarbaileyite has also been identified on this specimen, and on the type specimen of edoylerite deanesmithite is found in vugs and cavities associated with cinnabar and edoylerite. The host rock is composed of quartz, chalcedony, opal, magnesite, goethite, ferroan magnesiochromite and minor chlorite and dolomite. Other mercury-bearing minerals identified from the Clear Creek claim include szymańskiite, wattersite, metacinnabar, eglestonite, calomel, terlinguaite, mosesite, gianellaite, montroydite, and four unnamed mercury-bearing phases.
Deanesmithite most likely formed as a result of the reaction between a chromium-rich hydrothermal solution and pre-existing mercury-bearing minerals such as cinnabar.
Deanesmithite crystals are orange-red and transparent; the streak is the same colour but less intense. The mineral is brittle to friable, and possesses an irregular to subconchoidal fracture and an adamantine lustre (CM 31.4.787-793).
Deanesmithite from the Clear Creek Claim - Image

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