Terlinguaite

Terlinguaite
Terlinguaite, collected from Mariposa Mine, Terlingua District, Brewster County, Texas, United States
General
Category	Mineral
Formula (repeating unit)	Hg2ClO
Strunz classification	3.DD.20
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) H-M symbol: (2/m)
Space group	C2/c
Unit cell	a = 19.51 Å, b = 5.91 Å c = 9.47 Å; β = 143.81°; Z = 4
Identification
Color	Sulfur-yellow, greenish yellow, brown
Crystal habit	Aggregates of equant to elongated crystals, powdery, massive
Cleavage	Perfect on [101]
Tenacity	Brittle
Mohs scale hardness	2.5
Luster	Brilliant adamantine
Streak	Lemon-yellow, turning olive-green
Diaphaneity	Transparent to translucent
Specific gravity	9.22
Optical properties	Biaxial (-)
Refractive index	nα = 2.350 nβ = 2.640 nγ = 2.660
Birefringence	δ = 0.310
Pleochroism	Weak, green and yellow
2V angle	Measured: 20°
Alters to	turns olive-green on exposure to light
References	[1][2][3]

Terlinguaite is the naturally occurring mineral with formula Hg₂ClO. It is formed by the weathering of other mercury-containing minerals. Discovered in 1900 in the Terlingua District of Brewster County, Texas for which it is named.^[4] Its color is yellow, greenish yellow, brown or olive green.

References

1. Handbook of Mineralogy
2. Mindat.org
3. Webmineral data
4. Hillebrand, W. F.; W. T. Schaller (1907). "Art. XXVI. "The Mercury Minerals from Terlingua, Texas: Kleinite, Terlinguaite, Eglestonite, Montroydite, Calomel, Mercury"". The American Journal of Science (139): 259–274. Retrieved 2009-05-21.