You can see through it – Muscovite

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?

A Muscovite crystal - picture by Rob Lavinsky, iRocks.com

A Muscovite crystal – picture by Rob Lavinsky, iRocks.com

Muscovite is a layered silicate material, like talc which we posted about last week.  But unlike talc, this mineral is relatively strong and the layers can form into sheets as much as 15 m2.  And it is also transparent.  Muscovite’s ability to flake into large sheets and its transparency mean that it was used for windows before glass became more easily produced.  The name is in fact derived from this, as when used for windows it was known as Muscovy-glass.

Where did the structure come from?

This structure of Muscovite came from the American Mineral database.

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One thought on “You can see through it – Muscovite

  1. When you look at muscovite in thin section under a polarized microscope, you can see with crossed polars a feature called “bird’s eye” (http://www.youtube.com/watch?v=Bv3MVkyyxjk). Basically, when you put the mineral to extinction, you still can see light coming through.
    Maybe you can help me with the origin of this bird’s eye feature. I’ve heard that the interlayered K atoms deform the layers, so the optical properties change around them. But if you look up in Google, the main explanation is that the structure is deformed during the grinding process to make the thin section. Do you know which one is correct?

    Thanks in advance!!

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