Formula: HgCl (Hg1+Cl)
Normal halide, forms a series with kuzminite
Specific gravity: 7.15
Hardness: 1½ TO 2
Streak: Light yellowish white
Colour: Colourless, white, greyish, yellowish white, yellowish grey to ash-grey, brown; darkens upon exposure to light
Solubility: Insoluble in water, soluble in aqua regia
Calomel is an uncommon secondary mineral formed in the oxidised zone of
mercury-bearing deposits through the alteration of other
mercury minerals. Associated minerals include mercury and
its amalgams, cinnabar, mercury-bearing
calcite, limonite, and
(HOM, Dana, Mindat).
The type locality is Landsberg, Obermoschel, Nordpfälzer Land, Donnersberg District, Rhineland-Palatinate, Germany.
At El Doctor, Cadereyta Municipality, Queretaro, Mexico calomel occurs as an alteration of selenium-bearing metacinnabar (Dana ).
At the Funderburk prospect, Pike county, Arkansas, USA, calomel occurs in fractures in sandstone with artsmithite (Minrec 35.4.344).
At the Clear Creek claim, Goat Mountain, New Idria Mining District, San Benito county, California, USA, calomel occurs very rarely as coatings and crystals to 0.1 mm associated with native mercury, montroydite, cinnabar and, very rarely, hanawaltite (Minrec 36.4.342).
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