Images
Formula: HgCl (Hg1+Cl)
Chloride of mercury,
calomel group, forms a series with
kuzminite
Crystal System: Tetragonal
Specific gravity: 7.15 measured, 7.23 calculated
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
Luminescence: Fluoresces brick-red under UV
Solubility: Insoluble in water, soluble in aqua regia
Environments
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
tetrahedrite, eglestonite,
terlinguaite, montroydite,
kleinite, moschelite,
kadyrelite, kuzminite,
chursinite, kelyanite,
calcite, limonite, and
clay minerals
(HOM, Dana, Mindat).
Localities
The type locality is Landsberg, Obermoschel, Nordpfälzer Land, Donnersberg District, Rhineland-Palatinate, Germany.
Calomel from Landsberg - Image
At El Doctor, Cadereyta Municipality, Queretaro, Mexico calomel occurs as an alteration of
selenium-bearing metacinnabar
(Dana ).
At the Mariquita Mine (Sultana Mine), Usagre, Badajoz, Extremadura, Spain, calomel and
eglestonite are the two most common
secondary mercury
minerals.
In fractures in zones of late mineralisation with other
secondary mercury
minerals, calomel occurs as massive layers and as flattened crystals, exceeding 1 cm exceptionally, in shades
ranging from colourless through greyish, yellowish and orange-red. The calomel is associated with almost all
of the secondary
mercury species, most commonly with
eglestonite and native mercury,
less commonly with terlinguaite as well as with
rosasite and malachite .
In cavities in baryte, calomel is usually the only mineral species,
although it is associated rarely with mercury or
eglestonite. The calomel crystals usually have nearly equant
shapes reaching 1.5 cm in size. Most of these crystals are colourless although some show a slight greyish or
yellowish hue.
In other cavities, calomel forms large, thin, very delicate, white to transparent tabular crystals resembling
baryte which can reach 1 cm in size. The calomel crystals rest on
partially altered, earthy masses of cleavable calcite where they are
associated exclusively with eglestonite and
rosasite. Sometimes, the tabular calomel crystals are intergrown
with or even completely replaced by eglestonite. On the pinacoid faces
of these crystals another generation of calomel sometimes appears, as prismatic or pyramidal forms in parallel
growth. Similarly, calomel may sometimes be seen as epitactic growths on tabular crystals of
eglestonite, or as white, pseudocubic crystals of a late generation on
eglestonite.
(MinRec 55.4.491).
Calomel from the Mariquita Mine -
Image
At the Funderburk prospect, Pike county, Arkansas, USA, calomel occurs in fractures in
sandstone with artsmithite
(Minrec 35.4.344).
Calomel from Funderburk - Image
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).
Calomel from Clear Creek - Image
At the McDermitt Mine, Opalite Mining District, Humboldt County, Nevada, USA, calomel is associated with
kleinite and
terlinguacreekite in silicified volcanic rocks and sediments
(CM 43.1055-1060).
Calomel from the McDermitt Mine -
Image
At the Perry Pit, Mariposa Mine, Brewster County, Texas, USA, olive-brown light-tarnished calomel is associated
with powdery aggregates of lemon-yellow terlinguacreekite in a
calcite–gypsum vein
(CM 43.1055-1060).
Calomel from the Perry Pit - Image
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