Lorándite
Lorándite is a thallium arsenic sulfosalt with the chemical formula: TlAsS2. Though rare, it is the most common thallium-bearing mineral. Lorandite occurs in low-temperature hydrothermal associations and in gold and mercury ore deposits. Associated minerals include stibnite, realgar, orpiment, cinnabar, vrbaite, greigite, marcasite, pyrite, tetrahedrite, antimonian sphalerite, arsenic and barite.
| Lorándite | |
|---|---|
| General | |
| Category | Sulfosalt mineral |
| Formula (repeating unit) | TlAsS2 |
| IMA symbol | Lor |
| Strunz classification | 2.HD.05 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/a |
| Identification | |
| Color | Red to carmine-red, lead gray |
| Crystal habit | Prismatic tabular striated parallel to [001] |
| Cleavage | [100] perfect, [001] distinct |
| Fracture | Conchoidal |
| Mohs scale hardness | 2.0–2.5 |
| Luster | Sub-metallic – adamantine |
| Streak | Cherry-red |
| Diaphaneity | Subtransparent |
| Specific gravity | 5.53 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 2.720 |
| Pleochroism | Weak; Y = purple-red; Z = orange-red |
| Other characteristics | Tenacity: flexible, forming cleavage lamellae and fibers |
| References | |
The mineral is being used for detection of solar neutrino via a certain nuclear reaction involving thallium. It has a monoclinic crystal structure consisting of spiral chains of AsS3 tetrahedra interconnected by thallium atoms, and can be synthesized in the laboratory.
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