Amethyst
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| Amethyst | |
|---|---|
 Amethyst cluster frae Magaliesburg, Sooth Africae. | |
| General | |
| Category | Mineral variety |
| Formula (repeatin unit) | Silica (silicon dioxide, SiO2) |
| Creestal seestem | rhombohedral class 32 |
| Identification | |
| Colour | Purpie, violet |
| Creestal habit | 6-sided prism endin in 6-sidit pyramid (typical) |
| Twinnin | Dauphine law, Brazil law, an Japan law |
| Cleavage | None |
| Fractur | Conchoidal |
| Mohs scale haurdness | 7–lawer in impure varieties |
| Skinkle | Vitreous/glossy |
| Streak | White |
| Diaphaneity | Transparent tae translucent |
| Speceefic gravity | 2.65 constant; variable in impur varieties |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.543–1.553 nε = 1.552–1.554 |
| Birefringence | +0.009 (B-G interval) |
| Pleochroism | None |
| Meltin pynt | 1650±75 °C |
| Solubility | insoluble in common solvents |
| Ither chairacteristics | Piezoelectric |
Amethyst is a violet variety o quartz eften uised in jewelry. The name comes frae the Auncient Greek ἀ a- ("nae") an μέθυστος methustos ("intoxicatit"), a reference tae the belief that the stane pertectit its ainer frae drunkenness. The auncient Greeks an Romans wore amethyst an made drinkin vessels o it in the belief that it wad prevent intoxication. It is ane o several furms o quartz. Amethyst is a semiprecious stane an is the tradeetional birthstane for Februar.