Amethyst

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Amethyst
Amethyst. Magaliesburg, South Africa.jpg
Amethyst cluster frae Magaliesburg, Sooth Africae.
General
CategoryMineral variety
Formula
(repeatin unit)
Silica (silicon dioxide, SiO2)
Creestal seestemrhombohedral class 32
Identification
ColourPurpie, violet
Creestal habit6-sided prism endin in 6-sidit pyramid (typical)
TwinninDauphine law, Brazil law, an Japan law
CleavageNone
FracturConchoidal
Mohs scale haurdness7–lawer in impure varieties
SkinkleVitreous/glossy
StreakWhite
DiaphaneityTransparent tae translucent
Speceefic gravity2.65 constant; variable in impur varieties
Optical propertiesUniaxial (+)
Refractive indexnω = 1.543–1.553
nε = 1.552–1.554
Birefringence+0.009 (B-G interval)
PleochroismNone
Meltin pynt1650±75 °C
Solubilityinsoluble in common solvents
Ither chairacteristicsPiezoelectric

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.