Topaz is the gem of front line in the Race of colour stones. Its chemical formula is AL2(F,OH)2SIO4. Moreover its also in the hardness chart of Mohs scale hardness. Oftenly its found in clourless to pale yellowish colour.
Other naturally occurring colours
Pink,brown,orange,Light sahdes of purple,Light shades of green,Light shades of green.
Usually people confuse Yellowish variety of quartz (citrine) called sunehla with topaz. Also other stonnes like hedanite(yellow kunzite) also look same as topaz from color. But quartz,hedanite can’t compete topaz in luster. Topaz have bright viterous luster. Which matches the luster of corrundum(ruby,sapphire).
This gem belonging to Tertagonal crystal system is also apple of specimen collector’s eye. It sometimes contain phenomenal inclusions. Like calcite,fingers prints other tiny crystals. Specially bigger crystals with mother rock value too much. The surface features like penacoids and horizontal lines also make it eye catching.
Topaz is mostly transparent to translucent. That’s why it is preferable for jewelry. Another plus point is its tremendous size. As gigantic pieces of 700,800 grams are also not uncommon from (gilgit) Pakistan.
Brazil is a very important and famous source of topaz. With intresting colour hues of orange and brown.
Talking about the colours like SKY BLUE,LONDON BLUE,SWISS BLUE. These are all a result of Heating+radiation. I hope its not a new thing for the readers.
In explanation of this process I would like to add a few lines. Colourless topaz is first heated to attain wisky colour. Then radiation is passed which causes its colour to turn blue and that is stable. However the shympain colour of topaz which is the result of heating is not stable. And fades away with exposure to direct sunlight.
The rarest and the most appealing colour of topaz is the dark pink. That is only mined from Katlang(PAKISTAN). It can cost you $1000/ct if the piece is weigthing more than 5 ct. A really challenging thing for a facetter is to maintain the pink colour of stone. While cutting a slight mistake can make the colour fade.
Mostly the topaz which U see in market is treated somehow. But untill and unless the seller discloses it to the client. It’s all 100% fairplay and acceptable.