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) & traces of various transition elements. Rubies contain chromium as their dominant transition element and sapphires contain ferric iron. 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.
This video was shot by us at the sapphire mines at Bang Kacha in Thailand. The miners lease land from land owners and work the plot. The amount made from the mine production is split between the land owner and the miners. Once the miners have finished working the plot, the land is filled and trees are planted,
Where Rubies & Sapphires Come From
Rubies and sapphires are found in various countries around the globe. Some deposits produce large quantities, some produce only small amounts. Some produce fine quality stones others only produce lower quality stones. The supply of gem quality rubies is extremely low with only a handfull of deposits producing limited amounts. The best quality rubies are found at the legendary mines in the Mogôk valley, in Upper Burma. There are also rubies mined at Mong Hsu, also in Burma but these are of a lesser quality to those of Mogôk. Other noteworthy deposits are in Vietnam, Tajikistan, Afghanistan, Winza in Tanzania, Madagascar and Mozambique.
The finest sapphires found are from the legendary mines in Kashmir. These deposits were extensively mined from the late 1800's through to the early 1900's. There has been very little activity at these mines since then. Kashmir stones do come up in auctions from time to time but these stones fetch record prices. There are also some very fine sapphires mined in Mogôk, Upper Burma. Mogôk blue sapphires are generally the finest stones found in the market today.
Probably the biggest producing country of quality sapphires today is Madagascar. Stones from Madagascar are often mistakenly described as Sri Lankan. Large deposits of sapphires were discovered in the late 1990's. There is a wide variety of colours produced from the Madagascan deposits including blue, green, yellow and pink.
Fine sapphires are also mined in Sri Lanka in a variety of colours. Geologically Sri Lanka is very similar to Madagascar and the sapphires found are very similar in quality and colour to those found in Madagascar.
Thailand is also another major source of sapphires and small quantities or rubies. Large scale 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.
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.
There are other significant sapphire deposits include the Australian sapphire fields and the mines at Shandong province in China. Most of the Chinese material as are the Australian sapphires but like with other deposits there are exceptions and some fine stones are found at both these locations. There are also sapphires mined in the USA at Montana but these are mostly sold within the US.
