Topaz is an aluminium silicate containing fluorine and hydroxyl. Purely, it is colourless (white) ; it is the impurities which cause the variations of colour. “Topaz ranges from colourless to yellow, orange, red-brown, light to dark-blue, pink to red, violet and light-green.” Furthermore, Topaz is distinguished by its hardness and its perfect cleavage. This fine stone is found in Brazil, Afghanistan, Australia, Myanmar (Burma), China, Germany, Japan, Madagascar, Mexico, Namibia, Nigeria, Pakistan, Russia, Zimbabwe, Sri Lanka, Ukraine and in the USA.
Blue topaz are very rarely in the nature (deposits in Northern Ireland and UK), and there are only in a very pale blue colour. The other shades of blue result from techniques (irradiation and heating).
Tanzanite is a variety of Zoisite (calcium aluminum silicate ) and has a colour varying from blue to violet. This stone is Heat treatments enhance the Tanzanite’s colours. This gemstone is named “Tanzanite” because a deposit was found in 1967 in Tanzania, East African country. Tanzanite is distinguished by a perfect cleavage (it cleaves “without leaving any rough surfaces; a full, smooth plane is formed where the crystal broke”). Besides, Tanzanite is only found in Tanzania, East Africa.