November-Topaz

Colour	Variable
Formula	Al2(F,OH)2SiO4
Group	Silicates
Uses	Jewellery (not used in industry as very scarce)
Origins	Usually found in quartz
Locations	Sri Lanka, Brazil

Topaz is very rare with the finest samples being found in Brazil. It is very hard (8 on the mohs scale) and has a glassy appearance.

It can be lots of different colours, some due to the inclusion of traces of iron or chromium. Some colours are rarer than others. Yellow and orange tend to be the most valuable. (Pink opals are incredibly rare)

Colours can be changed by the addition of gamma rays.