Wattersite

Wattersite is a rare mercury chromate mineral with the formula Hg⁺¹₄Hg⁺²Cr⁺⁶O₆.[1] It occurs in association with native mercury and cinnabar in a hydrothermally altered serpentinite.[2] It was first described from Clear Creek claim, San Benito County, California, USA in 1961.[4] It was named to honor Californian mineral collector Lucius "Lu" Watters.[2]

Wattersite
Black crystals of wattersite with yellowish zones of edgarbaileyite. Locality: Clear Creek claim (Clear Creek Mine), Picacho Peak, New Idria District, Diablo Range, San Benito Co., California, USA. Dimensions: 6.6 cm x 4.8 cm x 4.1 cm
General
Category	Chromate mineral
Formula (repeating unit)	Hg^+14Hg^+2Cr^+6O6
Strunz classification	7.FB.15
Dana classification	35.4.2.1
Crystal system	Monoclinic
Crystal class	2/m
Space group	C2/c (number 15)
Unit cell	859.81 ų
Identification
Color	Dark red-brown to black
Crystal habit	Prismatic, aggregates, massive
Twinning	[001], contact twins on {100}
Cleavage	None
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	4.5
Luster	Sub-Metallic
Streak	Brick red
Diaphaneity	Opaque
Specific gravity	8.91
Optical properties	Biaxial
Refractive index	nα = 2.440 - 2.520 nγ = 2.700 - 2.860
Birefringence	δ = 0.260 - 0.340
Pleochroism	Visible
Dispersion	r > v strong
References	[1][2][3]

References

1. "Wattersite". MinDat. Retrieved 29 April 2017.
2. Handbook of Mineralogy
3. Groat, L.A.; Roberts, A.C.; Le Page, Y. (1995). "The crystal structure of wattersite, Hg4HgCrO6". The Canadian Mineralogist. 33: 41–46.
4. Roberts, Andrew C.; Bonardi, Maurizio; Erd, Richard C.; Criddle, Alan J.; Le Page, Yvon (1991). "Wattersite Hg+14Hg+2Cr+6O6 a new mineral from the Clear Creek claim San Benito Country, California". The Mineralogical Record. 22: 269–272.