A very rare gem – Uvarovite

In our travels on the internet we stumbled upon this page on ’10 beautiful minerals you won’t believe come from Earth’.   Fabulous pictures by Ryoji Tanaka, but what (we hear you cry) are the atomic arrangements behind these? We’ve covered one of them already (Gold) but we’ve picked out a couple of the others for this weekend.

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

What is it?

Uvarovite green crystals from Saranovskii Mine, Urals Region, Russia.  Photo by Rob Lavinsky, iRocks.com

Uvarovite green crystals from Saranovskii Mine, Urals Region, Russia. Photo by Rob Lavinsky, iRocks.com

This is the atomic arrangement of Uvarovite, which one of the rarest garnet minerals and found in the Urals of Russia. If it looks familiar… then it’s because you recall our post back in January on Garnets in general. Uvarovite is particular because in between the silicate tetrahedrons (show by blue silicon atoms sitting in the middle of four red oxygen atoms) sits calcium (grey atoms) and chromium (dark blue) atoms. It’s these metal atoms, which give this mineral its beautiful dark green colour.

Where did the structure come from?

Like many natural minerals, the structure of Uvarovite is complicated by the number of other elements that can substitute into the structure. The structure we’ve shown here was determined from a synthetic Uvarovite crystal in 2002; it is number #9007149 in the open crystallography database.

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