Amethyst

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Amethyst
Amethyst. Magaliesburg, South Africa.jpg
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 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.