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Corundum (var. sapphire)

Photograph of a group of sapphires from the National Gem Collection showing color variation
Photo by Chip Clark. Click to zoom.
SpecimenCatalog NumberLocalityWeight
Corundum (var. sapphire)NMNH G4371-00Sri Lanka42.2 ct
Corundum (var. sapphire)NMNH G3549-00Myanmar [Burma]92.6 ct
Corundum (var. sapphire)NMNH G3581-00Sri Lanka15.73 ct
Corundum (var. sapphire)NMNH G9808-0010.28 ct
Corundum (var. sapphire)NMNH G4357-00Sri Lanka31.06 ct
Corundum (var. sapphire)NMNH G2172-00Myanmar [Burma]16.8 ct
Corundum (var. sapphire)NMNH G4370-00Sri Lanka27.42 ct
Corundum (var. sapphire)NMNH G3875-00Sri Lanka22.4 ct
Corundum (var. sapphire)NMNH G4372-00Sri Lanka19.9 ct
Corundum (var. sapphire)NMNH G3106-00Sri Lanka15.2 ct

Sapphire is a gem variety of the mineral corundum. Pure corundum is colorless, but small amounts of impurities in the crystal structure can produce a range of vivid colors. A few atoms of chromium tint corundum the deep red color of ruby, the most prized corundum gem. Iron and titanium, on the other hand, are responsible for the deep blue color of sapphire. Other impurity atoms can color corundum crystals a range of hues, from pink, yellow, and orange to purple, green, and even black. Corundum gems other than red or blue are called fancy colored sapphires. The fancy colored sapphires pictured here range in size from 10.3 to 92.6 carats. The green and large yellow sapphires are from Burma; the others are from Sri Lanka.


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