Amethyst

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Amethyst
Amethyst. Magaliesburg, South Africa.jpg
Amethyst cluster frae Magaliesburg, Sooth Africae.
General
Category Mineral variety
Formula
(repeating unit)
Silica (silicon dioxide, SiO2)
Identification
Color Purpie, violet
Crystal habit 6-sided prism endin in 6-sidit pyramid (typical)
Crystal seestem rhombohedral class 32
Twinnin Dauphine law, Brazil law, an Japan law
Cleavage None
Fractur Conchoidal
Mohs scale hairdness 7–lawer in impure varieties
Luster Vitreous/glossy
Streak White
Diaphaneity Transparent tae translucent
Specific 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 characteristics Piezoelectric

Amethyst is a violet variety o quartz eften uised in jewelry. The name comes frae the Auncient Greek 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 would prevent intoxication. It is ane o several furms o quartz. Amethyst is a semiprecious stane an is the tradeetional birthstane for Februar.