Emerald
Emeralds are a variety of the mineral beryl (Be3Al2(SiO3)6,) colored green by trace amounts of chromium and sometimes vanadium.. Beryl has a hardness of 7.5 - 8 on the 10 point Mohs scale of mineral hardness. Most emeralds are highly included, so their brittleness (resistance to breakage) is classified as generally poor. The origin of the word "emerald" is said to be a Sanskrit word meaning "green".
General
Category Beryl variety
Chemical formula Beryllium aluminium silicate with chromium, Be3Al2(SiO3)6::Cr
Identification
Color Green
Crystal habit Hexagonal Crystals
Crystal system Hexagonal
Cleavage Poor Basal Cleavage (Seldom Visible)
Fracture Conchoidal
Mohs Scale hardness 7.5 - 8.0
Luster Vitreous
Refractive index 1.576 - 1.582
Pleochroism Distinct, Blue-Green/Yellow-Green
Streak White
Specific gravity 2.70 - 2.78
Category Beryl variety
Chemical formula Beryllium aluminium silicate with chromium, Be3Al2(SiO3)6::Cr
Identification
Color Green
Crystal habit Hexagonal Crystals
Crystal system Hexagonal
Cleavage Poor Basal Cleavage (Seldom Visible)
Fracture Conchoidal
Mohs Scale hardness 7.5 - 8.0
Luster Vitreous
Refractive index 1.576 - 1.582
Pleochroism Distinct, Blue-Green/Yellow-Green
Streak White
Specific gravity 2.70 - 2.78
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