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Pleochroism in Minerals and Gemstones



piece of a transparent mineral with pleochroism



What is the Meaning of Pleochroism?

Pleochroism is an optical phenomenon seen in certain minerals and gemstones.  Depending on the angle from which the stone is viewed different colours can be seen.

Pleochroism can be useful in helping to identify certain minerals because stones that share a very similar colour will often have different pleochroic colour schemes.

Although amethyst exhibits pleochroism it's fairly weak.  In tourmaline, tanzanite and apatite it's strong.

The word pleochroism comes from the Greek words pléōn meaning 'more' and khrôma meaning 'colour'.

Pleochroism is caused by the way light passes through a mineral's crystal struture.



tanzanite crystal exhibiting pleochroism
Pleochroism in Tanzanite. Photo courtesy of Stan Celestian. Clickable image



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