Montbrayite
| Montbrayite | |
|---|---|
Montbrayite (Montbray, Quebec) | |
| General | |
| Category | Sulfosalt minerals |
| Formula | (Au,Ag,Sb,Bi,Pb)23(Te,Sb,Bi,Pb)38 or (Au,Sb)2Te3 |
| IMA symbol | Mnb |
| Strunz classification | 2.DB.20 |
| Crystal system | Triclinic |
| Crystal class | Plumbo-telluride |
| Identification | |
| Color | cream, yellowish white, very light yellow |
| Crystal habit | small segregations, rarely exceeding 3-5 mm, crystals very rare |
| Twinning | observed |
| Cleavage | very good {110}, {011}, {111} |
| Fracture | irregular to uneven, sub-conchoidal, the mineral is very fragile |
| Tenacity | very brittle |
| Mohs scale hardness | 2.5 |
| Luster | metallic |
| Diaphaneity | opaque |
| Density | 9.94 (measured) |
| Pleochroism | very weak |
Montbrayite (from a Canadian toponym) is a very rare mineral from among the gold tellurides, close to krennerite and calaverite, in composition it is a mixed polymetallic plumbo-telluride of gold with a variable formula, initially written as Au2Te3,: 20–21 or (Au,Sb)2Te3, but today having a much more complex form in the calculated form: (Au,Ag,Sb,Bi,Pb)23(Te,Sb,Bi,Pb)38. The color of montbrayite is cream, tin-white to pale yellow, the luster is metallic.