Tanzanite

IBDP Teacher Blogs, Chemistry | September 28, 2011
Tanzanite

Chances are you will not have heard of Tanzanite but it is considered to be the worlds newest precious stone. Not newest as in the age of the stone but newest as it was only discovered in 1967.

It is also rarer than diamond and is only found in an 13 square kilometre area on northern Tanzania. The stone is much sought after due to ….

…. its lavender blue colour.

By Didier Descouens (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

The mineral is calcium aluminium silicate hydroxide which is grey / brown mineral. However, when it is heated to around 400 oC it turns the beautiful colour that you see in the above image. The blue colour comes from trace amounts of vanadium.

The stone was formed when super-heated was dissolved metals and minerals in the earths crust and moved towards the earth surface, cooling and allowing the mineral to crystallise.

The largest lump so far found has come in at a mighty 3 Kg. It is named ‘Mawenzi’, after Kilimanjaro’s second highest peak.

Why no name it after the highest peak? Well, you never know what may be pulled out of the ground tomorrow? :mrgreen:

This article was adapted from the article ‘Tanzanite’ published on page 52 in the 24th September 2005 edition of New Scientist magazine.

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