Color: Colorless, yellow, red-brown, light blue, pinky red, pale green
Hardness: 8 Mohs
Specific Gravity: 3.35 - 3.56
Refractive Index: 1.610 - 1.638
In the past all yellow and brown gemstones were called "topaz". With advancement of technology we can happily distinct topaz from the less valuable gemstones such as citrine. A variety of impurities and treatments may make topaz wine red, pale gray, reddish-orange, pale green, or pink (rare), and opaque to transparent.
Important Topaz deposits in the world
Today's most important mines are located in Brazil, Sri Lanka, Burma, and Russia. Some clear topaz crystals from Brazil can reach boulder size and weight hundreds of pounds.
Most desirable Topaz color is pink and orange
Colored topaz are rarely vivid. The most common color is yellow with a red tint. The most valuable is pink. Orange topaz also known as precious topaz. Some topaz can fade on exposure to sunlight.
Topaz must be carefully handled
Although topaz is very hard, they must must be treated with greater care than some other gemstone of similar hardness (such as sapphire, ruby) because of a weakness of atomic bonding in different planes. This gives topaz a tendency to fracture along such a plane if struck with sufficient force. An experienced stone setting would have a good knowledge on how to set topaz into jewelry.