Christite: Properties and Occurrences

Christite is a mineral with the chemical formula TlHgAsS3. It is a monoclinic-prismatic mineral containing arsenic, mercury, sulfur, and thallium. 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 is an anisotropic mineral, which means that it exhibits different properties when measured in different directions. In the 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 polar crossed and sees the mineral change colors when it is rotated.

General Information

  • Category: Sulfosalt mineral
  • Formula: TlHgAsS3
  • Crystal system: Monoclinic
  • Crystal class: Prismatic (2/m) (same H-M symbol)

Properties

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. 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.

  • Formula mass: 576.09 g/mol
  • Color: Crimson red, bright orange.
  • Crystal habit: Subhedral grains, may be somewhat bladed or flattened
  • Fracture: Uneven
  • Mohs scale hardness: 1-2
  • Luster: Adamantine
  • Streak: light orange
  • Diaphaneity: opaque to semitransparent
  • Specific gravity: 6.2

Occurrence

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

Association: Realgar, orpiment, lorandite, barite, getchellite (Carlin mine, Nevada, USA); lorandite, barite, marcasite, pyrite (Lanmuchang deposit, China).

 

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