Rubies & Sapphires
About Rubies & Sapphires ...
The name corundum originates from the Sanskrit word kurivinda. It is used to describe the group of gemstones to which both ruby and sapphire belong. The chemical composition of corundum is aluminium oxide (Al2O3) with traces of various additional elements in traces, such as chromium, ferric iron & titanium. Corundum crystallizes in a hexagonal (trigonal) form with the six crystal faces meeting at 120 degrees. Gem quality corundum comes in all colours with red corundum described as ruby and all other colours described as a sapphire with the name of the colour as a prefix. Below are some of the physical properties of corundum.
| Refractive Index | 1.762 - 1.770 |
| Birefringence | 0.008 - 0.009 |
| Crystal System | Hexagonal (trigonal) |
| Optic Character | Uniaxial (-) |
| Specific Gravity | 3.97 - 4.03 |
| Hardness | 9 |
| Pleochroism | Very Pronounced |
| Chemical Composition | Aluminium Oxide (Al2 O3) |
| Cleavage | None |
| Dispersion | 0.008 |
Mining For Sapphires...
Presently the largest producing country of fine quality sapphires today is Madagascar. Many Madagascan sapphires are often mistakenly identified as being from Sri Lanka. The quality of sapphires from both these countries is remarkably similar. Large deposits of sapphires were discovered in Madagascar during the late 1990's and are still actively mined today. There are a wide variety of colours produced from the Madagascan deposits including blue, green, yellow and pink. Sri Lanka is also a major supplier of sapphires in a variety of colours.
Other important sources of rubies and sapphires are Mogok in Burma, China, Australia, Montana USA, and the ruby mines at Montepuez in Mozambique.
Rough blue sapphire crystals from Mogok.
Thailand is also another source of sapphires and small quantities of rubies. Mining operations can be found to the west at Kanchanaburi and to the east at Bang Kacha. Kanchanaburi produced mostly commercial grade blue sapphires but some very fine gems have been unearthed there. Other colours are found in Kanchanaburi but only in very small quantities. For many years Kanchanaburi was the world's largest producer of blue sapphires but due to rising production costs mining activity is now mostly small scale operations.
Bang Kacha to the east produces mostly green and golden-orange coloured sapphires. Some of the golden coloured stones can be quite stunning. There are small quantities of blue sapphires found here as are black and golden star sapphires.
