Sapphire

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Sapphire
Logan Sapphire SI.jpg
The 423-carat (85 g) blue Logan sapphire
General
Category Oxide mineral
Formula
(repeating unit)
aluminium oxide, Al2O3
Identification
Color Often Blue but varies
Crystal habit massive an granular
Crystal seestem Trigonal
Seembol (32/m)
Space Group: R3c
Cleavage none
Fractur conchoidal, splintery
Mohs scale hairdness 9.0
Luster vitreous
Streak white
Specific gravity 3.95–4.03
Optical properties Abbe nummer 72.2
Refractive index nω=1.768–1.772
nε=1.760–1.763,
Birefringence 0.008
Pleochroism Strang
Meltin pynt 2030–2050 °C
Fusibility infusible
Solubility Insoluble
Ither characteristics coefficient o thermal expansion (5.0–6.6)×10−6/K

Sapphire (Greek: σάπφειρος; sappheiros, 'blue stane',[1] which probably referred instead at the time tae lapis lazuli) is a gemstone variety o the mineral corundum, an aluminium oxide (α-Al2O3). Trace amoonts o other elements such as airn, titanium, chromium, copper, or magnesium can give corundum blue, yellae, purpie, orange, or a greenish color. Chromium impurities in corundum yield a pink or reid tint, the latter bein cried a ruby.

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