Agate

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Agate
Moss agate pebble, 2.5 cm (1 inch) long
General
CategoryQuartz variety
Chemical formulaSilica, SiO2
Identification
ColorWhite to grey, light blue, orange to red, black.
Crystal habitCryptocrystalline silica
Crystal systemRhombohedral Microcrystalline
CleavageNone
FractureConchoidal with very sharp edges.
Mohs scale hardness7
LusterWaxy
StreakWhite
Specific gravity2.58-2.64
Refractive index1.530-1.540
Birefringenceup to +0.004 (B-G)
PleochroismAbsent

Agate