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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
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 -
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