|
 |
 Topaz |
| Crystal structure : Orthorhombic |
Composition : Neosilicate of aluminium |
| Specific gravity : 3.53-3.56 |
Hardness : 8 |
| Refractive index : 1.618-1.638 |
Birefringence : 0.008-0.010 |
| Variety : |
Pleochroïsm : weak from blue, distinct for yellow, strong for pink |
Cut :       |
Topaz has several colors :
- blue
- green : very rare
- yellow
- pink : from pale to vivid
- colorless
|
Its most required colour is pink but also the green for its rarity, the most common color being the yellow and not blue as we could believe it by looking at the windows of the jewelleries !
The colors of topazes are seldom brilliant.
Caution: we can change the color of a topaz by heating it: a yellow topaz can become a pink, blue or colourless topaz ! |
 |
The origin of its name is not clearly identified: for some, it takes one's name from the island of Topazos in the Red Sea, for others, it takes from Sanskrit “tupas” meaning “fire”.
Formerly, all the yellow or brown gilded stones were called topaz.
A topaz belongs to the very exclusive club of the famous stones: the “Bragance”. This colourless topaz (1640 cts), on the crown of Portugal, was taken for a long time for a diamond! |
|
| Deposits : |
| The countries having deposits are : |
Country |
Quantity |
Quality |
Comment |
| Brazil |
|
|
|
| Sri Lanka |
|
|
|
| United states |
|
|
|
| Madagascar |
|
|
|
| Australia |
|
|
|
| Japan |
|
|
|
|
|
|
