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Formula: Hg2OCl
Hg1+Hg2+OCl
Oxyhalide of mercury
Crystal System: Monoclinic
Specific gravity: 8.725 measured, 8.73 calculated
Hardness: 2 to 3
Streak: Lemon yellow
Colour: Yellow, yellow-green, brown, darkens to olive-green on exposure to light, pale olive-green in transmitted light
Environments
Terlinguaite is a rare secondary mineral in hydrothermal
mercury deposits. Associated minerals include
cinnabar, metacinnabar,
eglestonite, kleinite,
montroydite, calomel and
mercury
(HOM).
Localities
At the Mariquita Mine (Sultana Mine), Usagre, Badajoz, Extremadura, Spain, terlinguaite is a common mineral,
usually seen as cryptocrystalline earthy crusts or compact masses, with a characteristic lemon-yellow colour that
differentiates it from eglestonite. Common associations include
montroydite, eglestonite,
native mercury and
edgarbaileyite. Translucent to transparent
calcite commonly contains inclusions of terlinguaite which form
beautiful phantoms parallel to the crystal faces. Rarely, terlinguaite forms excellent olive-green to greenish
yellow prismatic crystals to 4 mm. The specimens from Usagre are among the best in the world
(MinRec 55.4.508).
Terlinguaite from the Mariquita Mine -
Image
At the Clear Creek claim, Goat Mountain, New Idria Mining District, San Benito county, California, USA,
terlinguaite is very rare, but has been found associated with
eglestonite and montroydite
(Minrec 36.4.350).
Terlinguaite from Clear Creek -
Image
At the type locality, the Terlingua Mining District, Texas, USA, terlinguaite is associated with
calomel, eglestonite,
kleinite, montroydite,
mercury and cinnabar
(Dana).
Terlinguaite from Terlingua - Image
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