Tuesday, 15 December 2009

Flair of the dog

Feldspars are a large group of silicate minerals that are important in the formation of igneous rocks, but show up in sedimentary and metamorphic rocks too. Labradorite is a plagioclase feldspar, named for Labrador in Canada - the type locality is Paul's Island. Its crystals show lamellar twinning; thin, interlocking plates. When light reflects off these crystals there is a fantastic play of colour across the surface of the stone. This is called schiller effect (or more properly in this case - labradorescence). Most of the material commercially available is from Maniry in Madagascar, though there's a high grade called Spectrolite from Finland.

What you DO need to know is that it's pretty.

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