Jump to navigation Jump to search
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.);


Corundum SR-ATR RRUFF R040096.png

Raman (RRUFF)

Corundum Raman RRUFF R040096.png

Raman (U of Parma)


Physical and Chemical Properties

  • Insoluble in acids and alkalis.
  • Trigonal crystal system.
  • Fracture = conchoidal or splintery
  • Luster = vitreous to subadamantine
  • Streak = white
  • Fluorescence = generally inert. Might fluoresce red to orange under LW. Weak chalky blue or green under SW may indicate heat treatment
  • Pleochrosism = moderate to strong blue-violet to blue-green dichroism
  • Inclusions = may have fine needle-like rutile inclusions; hexagonal growth or color banding; or twinning planes
Mohs Hardness 9.0
Density 3.96-4.05 g/ml
Refractive Index 1.762 - 1.770
Birefringence 0.008-0.010


Properties of Common Abrasives

Properties of Common Gemstones

Additional Images

Resources and Citations

  • Gem Identification Lab Manual, Gemological Institute of America, 2016.
  • 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
  • Encyclopedia Britannica, Comment: "sapphire." Accessed 15 Sept. 2005.
  • Wikipedia: Sapphire (Accessed Sept. 14, 2005 and Dec 2022)
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976