| Fine ruby is the rarest and most valuable of all colored gemstones. Burma is the traditional source for fine ruby, with new material coming from Madagascar, Tanzania and Mozambique. Treatment is common. Heat treatment has been used for centuries. It is used to improve the clarity and colour of rubies. The ruby is placed in a crucible and heated to around 1800 degrees. |  |
 
| In 2004, a gem lab in Chanthaburi, Thailand developed a technique to improve the appearance of rubies. Previously undesirable gems could be repaired using heat treatment with lead glass. The refractive index of corundum and lead glass are similar, allowing light to travel through the stone and improving color and clarity. Fracture-filled rubies sell at a fraction of the cost of untreated rubies of similar color. |  
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