February-Amethyst

Colour	Purple or blue violet
Formula	SiO2 also contains iron
Group	Oxides (member of quartz group)
Uses	Used by ancient Egyptians for jewellery
Origins	Found in geodes or alluvial deposits
Locations	Urals, Sri Lanka, Madagascar

Amethyst is fairly hard (7 on the mohs scale). It is classed as semiprecious because the colour is unpredictable and often needs to be artificially enhanced. It is usually purple (similar in appearance to corderite) but sometimes only on the edges. The colour can be more evenly distributed by heating but if it is heated too much it becomes yellow and turns into citrine. Perfectly coloured amethysts are rare.