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Formula: ([Hg1+]2)3OCl3(OH)
Hydroxyhalide, forms a series with kadyrelite
Specific gravity: 8.33 to 8.45
Hardness: 2½
Streak: Yellow to greenish yellow
Colour: Yellow, orange-yellow, brown, turns dark brownish, then black, on exposure to light, yellow-brown to brown
in transmitted light
Solubility: Decomposed by acids with separation of calomel
Environments
Sedimentary environments
Hydrothermal environments
Eglestonite is an oxidation product of other mercury minerals such
as native mercury and cinnabar
(Mindat).
Localities
At the Kadyrel' Hg occurrence, Oorash-Khem River Valley, Uyuk Range, Pi-Khem District, Tuva, Russia, eglestonite
occurs with lavrentievite,
calomel, mercury and
kadyrelite
(HOM).
At the Funderburk prospect, Pike county, Arkansas, USA, eglestonite occurs
in fractures in sandstone with artsmithite and other
mercury minerals
(Minrec 35.4.344).
At the Clear Creek claim, Goat Mountain, New Idria Mining District, San Benito county, California, USA,
eglestonite is most often associated with edgarbaileyite,
native mercury, cinnabar and
wattersite coating quartz cavities
(Minrec 36.4.346-347).
At the Challenge deposit, Redwood City, San Mateo county, California, USA, eglestonite is associated with
cinnabar, mercury and
calomel
(HOM).
At the type locality, the Terlingua Mining District, Texas, USA, eglestonite is associated with
calomel, mercury,
terlinguaite, montroydite
and calcite
(HOM).
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