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From Wikipedia, the free encyclopedia
Dawsonite is a mineral composed of sodium aluminium carbonate hydroxide, chemical formula NaAlCO3(OH)2. It crystallizes in the orthorhombic crystal system. It is not mined for ore. It was discovered in 1874 during the construction of the Redpath Museum in a feldspathic dike on the campus of McGill University on the Island of Montreal, Canada.[2] It is named after geologist Sir John William Dawson (1820–1899).[3]
| Dawsonite | |
|---|---|
Dawsonite from Mont Saint-Hilaire, Rouville RCM, Montérégie, Québec, Canada | |
| General | |
| Category | Carbonate minerals |
| Formula (repeating unit) | NaAlCO3(OH)2 |
| IMA symbol | Dws[1] |
| Strunz classification | 5.BB.10 |
| Dana classification | 16a.03.08.01 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Imam |
| Identification | |
| Formula mass | 144.00 g/mol |
| Color | white |
| Crystal habit | encrustations or radial |
| Cleavage | perfect on {110} |
| Fracture | uneven |
| Mohs scale hardness | 3 |
| Luster | vitreous |
| Streak | white |
| Diaphaneity | transparent |
| Specific gravity | 2.436 |
| Refractive index | nα = 1.466 nβ = 1.542 nγ = 1.596 |
| Birefringence | δ = 0.130 |
| 2V angle | 77° |
| References | [2][3] |
The type material is preserved in the collection of the Redpath Museum.[2]
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