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Logan Sapphire SI.jpg
The 423-carat (85 g) blue Logan sapphire
Category Oxide mineral
(repeating unit)
aluminium oxide, Al2O3
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
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 gemstane variety o the mineral corundum, an aluminium oxide (α-Al2O3). Trace amoonts o ither elements sic as airn, titanium, chromium, copper, or magnesium can gie corundum blue, yellae, purpie, orange, or a greenish colour. Chromium impurities in corundum yield a pink or reid tint, the latter bein cried a ruby.

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