What is our planet made out of? 2) Olivine

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?

Many olivine crystals have a lovely grass-green colour to them.  Photo taken by Azuncha

Many olivine crystals have a lovely grass-green colour to them. Photo taken by Azuncha

Olivine, like feldspar, comes in two main types (known as forsterite and fayalite) but unlike the feldspar minerals the crystal structure of these are both the same.  The difference is that forsterite has magnesium atoms living in between the silicate tetrahedra, and fayalite had iron instead. Most natural olivine actually has a mixture of iron and magnesium atoms within them. Olivine is an important mineral in the crust under the sea, but also in the first part of the mantle – the increasingly hot beginning of our Earth’s interior. Olivine is also, apparently, the ideal rock to use as hot stones in saunas. This is because of its high density and resistance to weathering.

Where did the structure come from?

The structure of olivine as originally determined by WL Bragg is #1010497 in the open crystallographic database.

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