Sapphire

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Sapphire
Logan Sapphire SI.jpg
The 423-carat (85 g) blue Logan sapphire
General
CategoryOxide mineral
Formula
(repeatin unit)
aluminium oxide, Al2O3
Creestal seestemTrigonal
Seembol (32/m)
Space Group: R3c
Identification
ColourOften Blue but varies
Creestal habitmassive an granular
Cleavagenone
Fracturconchoidal, splintery
Mohs scale haurdness9.0
Skinklevitreous
Streakwhite
Speceefic gravity3.95–4.03
Optical propertiesAbbe nummer 72.2
Refractive indexnω=1.768–1.772
nε=1.760–1.763,
Birefringence 0.008
PleochroismStrang
Meltin pynt2030–2050 °C
Fusibilityinfusible
SolubilityInsoluble
Ither chairacteristicscoefficient o thermal expansion (5.0–6.6)×10−6/K

Sapphire (Greek: σάπφειρος; sappheiros, 'blue stane',[1] which probably referred insteid 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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