Christite

Christite crystals

General
Category| Sulfosalt mineral
Formula
(repeating unit)| TlHgAsS3
IMA symbol| Cri[1]
Strunz classification| 2.HD.15
Crystal system| Monoclinic
Crystal class| Prismatic (2/m)
(same H-M symbol)
Space group| P21/n
Unit cell| a = 6.113 Å, b = 16.188 Å,
c = 6.111 Å; β = 96.71°;
V = 600.59 Å3; Z = 4
Identification
Formula mass| 576.09 g/mol
Color| Crimson red, bright orange.
Crystal habit| Subhedral grains, may be somewhat bladed or flattened
Cleavage| {010} and {110} perfect, {101} good
Fracture| Uneven
Mohs scale hardness| 1-2
Luster| Adamantine
Streak| light orange
Diaphaneity| opaque to semitransparent
Specific gravity| 6.2
Optical properties| Biaxial
Pleochroism| Weak to strong, grayish green, dark violet, bluish violet
References| [2][3][4]

Christite is a mineral with the chemical formula TlHgAsS3. It is named after Dr. Charles L. Christ, a member of the U.S. Geological Survey. It usually comes in a crimson red or bright orange color. It has a density of 6.2 and has a rating between 1 and 2 on Mohs Hardness Scale. Christite has an adamantine luster and leaves behind an orange streak.[3] Its crystal system is monoclinic with possible crystal classes of twofold symmetry, mirror plane symmetry, and twofold with a mirror plane. This means it can have radial symmetry, mirror plane symmetry, or mirror plane symmetry perpendicular to the two-fold axis.[5] It is an anisotropic mineral, which means that it exhibits different properties when measured in different directions. In plane polarized light, its color is golden yellow. It is birefringent, which means that it has two distinct indices of refraction. This can be seen when one looks through the microscope with both polars crossed and sees the mineral change colors when it is rotated.

## Occurrence

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Christite occurs with baryte in hydrothermal veins in dolomite at the Carlin mine in Nevada and in pods within a mercury deposit, the Lanmuchang deposit, China.[4] It occurs associate with realgar, orpiment, lorandite, baryte and getchellite at the Carlin mine and with lorandite, baryte, pyrite and marcasite in the Lanmuchang.[4]

## References

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1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
2. ^ Mineralienatlas
3. ^ a b Ralph, Jolyon; Chau, Ida (6 September 2010). "Christite". mindat.org - the mineral and locality database. Retrieved 15 September 2010.
4. ^ a b c Handbook of Mineralogy
5. ^ Fleischer, M., and Mandarino, J.A. (1991) Glossary of mineral species (Sixth edition). 38 p. Mineralogical Record, Tucson, Arizona.

* Brown, K.L., Dickson, F.W, Radtke, A.S., and Slack, J.F. (1977) Christite, a new thallium mineral from the Carlin gold deposit, Nevada. American Mineralogist, 62, 421-425.

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