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Oval gem
MFA# 01.7543


Sapphire, uncut

A transparent blue Gemstone composed of Corundum (aluminum oxide). Sapphires range in color from a pale blue to a deep indigo. They are mined in Myanmar (formerly Burma), Thailand, Kashmir, Sri Lanka, Australia (Victoria, Queensland, New South Wales), India, Madagascar, Russia, South Africa, and the U.S. (Montana, North Carolina). Sapphires are extremely hard and durable gemstones that have been used in jewelry since 1200 BCE. Oriented rutile crystal inclusions in a sapphire can produce a six-sided star effect called a Star Sapphire. Synthetic sapphires, produced commercially since 1902, are used in jewelry, watches, phonograph needles, instrument bearings, optical elements, and as abrasives.

Synonyms and Related Terms

corundum; alumina; aluminum oxide; star sapphire; safir (Dan.; Sven.); Saphir (Deut.); zafiro (Esp.); saphir (Fr.); saffier (Ned.); szafir (Pol.); safira (Port.);



Physical and Chemical Properties

  • Insoluble in acids and alkalis.
  • Trigonal crystal system.
  • Strongly pleochroic.
  • Fracture = conchoidal or splintery
  • Luster = vitreous
  • Streak = white
Composition Al2O3
CAS 1317-82-4
Mohs Hardness 9.0
Melting Point 2040 C
Density 3.96-4.05 g/ml
Refractive Index 1.80
Boiling Point 1.76-1.78 C


Properties of Common Abrasives

Properties of Common Gemstones

Additional Images

Resources and Citations

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 693
  • R.M.Organ, Design for Scientific Conservation of Antiquities, Smithsonian Institution, Washington DC, 1968
  • Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
  • R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997
  • A.Lucas, J.R.Harris, Ancient Egyptian Materials and Industries, Edward Arnold Publishers Ltd., London, 4th edition, 1962 Comment: 1200-500 BC
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976

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