Natural Color Diamonds in the 21st Century.

CareĬonsult our gemstone care guide for recommended cleaning methods.

Specific gemstones of significant size are described in the ruby and sapphire entries. Montana sapphires over 1 carat are very rare, but the blue ones in this size range are magnificent. Large sapphires have been found in Australia. Malawi material (sapphire) reaches a size of about 12 carats. A 1400 gram ruby was found in Yugoslavia (Prilip) but was not gemmy. Enormous sapphires of fine color and transparency have been found in the gem gravels of Sri Lanka and Burma. Fine gem rubies of large size occur in the Sri Lankan gravels, with smaller ones from Burma and Thailand. The largest rubies come from the chrome-zoisite matrix in Tanzania, but these are not really of gem quality. A ruby of 30 carats is a great rarity, whereas sapphires in museum collections weighing hundreds of carats are not uncommon. Sapphires, in general, reach a far greater size than rubies. Gem-quality corundum is occasionally found in the Czech Republic, Finland, Greenland, Nepal, Norway, Pakistan, Russia, and Slovakia. For location details, see Identifying Origins of Rubies and Sapphires.

Rubies and sapphires are found worldwide. See corundum treatments for more information. Lead glass filling: Fills fractures, improves clarity. CORUNDUM: Sapphire-Star sapphire, Sri Lanka (31.87). Very rarely there are two distinct sets of needles oriented according to the first and second order prisms of the corundum (30° apart), resulting in a strong, 12-rayed star.įor more information on corundum inclusions, see Identifying Origins of Rubies and Sapphires. When such material is cut into a cabochon the sheen is concentrated along the top of the stone into three white lines crossing at 120° angles, creating a six-rayed star. The rutile needles orient themselves according to the hexagonal symmetry of the corundum, and reflections from these needles provide a chatoyancy. Star corundum gemstones show asterism, or a 'star effect.' This phenomenon is created by the inclusion of rutile needles within the host corundum crystal. Among sapphires the green gems are more iron-rich, have higher indices.ĬORUNDUM: Star ruby, Sri Lanka (2.75), Burma (2.6, 0.62), India (8.4). Synthetics: See Identifying Inclusions and Synthetic Gemstones and Their Identification.Ĭharacteristics of Corundum from Various Localities

Ruby sapphire gem