| Tsugaruite | |
|---|---|
 Pb28As15S50Cl | |
| General | |
| Category | Sulfosalt mineral |
| Formula | Pb 28 As 15 S 50 Cl |
| IMA symbol | Tsg [1] |
| Strunz classification | 2.JB.30 |
| Crystal system | Orthorhombic |
| Space group | Pnn2 (space group 34) |
| Unit cell | a = 8.0774(10) Å, b = 15.1772(16) Å, c = 38.129(4) Å; Z = 16 |
| Identification | |
| Color | Lead-grey |
| Crystal habit | Tabular |
| Cleavage | None observed |
| Fracture | Irregular/uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 2.5 to 3 |
| Luster | Metallic |
| Streak | Lead-grey |
| Diaphaneity | Opaque |
| Specific gravity | 6.83 (Calculated) |
| Density | 6.83 g/cm3 (Calculated) |
| Optical properties | Weakly bireflectant |
| Pleochroism | Weakly pleochroic |
| References | [2] |
Tsugaruite is a sulfosalt mineral with the chemical formula Pb28As15S50Cl. It was first discovered in 1997 in a thin baryte veinlet at the Yunosawa mine in Ikarigaseki, Aomori. In 1998, the International Mineralogical Association approved it as a new mineral species. [1] [3] The mineral was named for its type locality's location in Japan's Tsugaru Peninsula.
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When tsugaruite was originally discovered, its structure was uncertain and its chemical formula was believed to be Pb4As2S7. [1] Tsugaruite has a hardness of 2.5-3 on the Mohs scale and is described as "opaque with a metallic lustre and lead-grey streak". [1] It is associated with jordanite and galena. The chemical similarity of tsugaruite to jordanite has caused confusion, resulting in earlier findings of tsugaruite being classified as jordanite. [1] [4] It is orthorhombic and occurs as radiating groups of tabular crystals. [1] [5] The structure is highly complex which is indicated by its large unit cell of 4674.3(9) Å3. [3] [6] It is in space group Pnn2. [3] Tsugaruite is recognized as the first lead-arsenic chloro-sulfosalt. [3] Compared to jordanite, tsugaruite is slightly softer and darker, slightly greener, less pleochroic, and less anisotropic. [1] Chlorine occupies a specific position in its structure. This was discovered using electron probe microanalysis. The atomic ratio of tsugaruite is close to that of other lead-antimony chloro-sulfosalts and just above the atomic ratio of dadsonite. [3] Tsugaruite is found with jordanite but formed later. Due to its rarity, tsugarite is mostly studied for its mineralogical properties. Practical uses are still being researched, [1] primarily with X-ray crystallography. [3]