Saturday, August 24, 2013

Geo-Shopping: Labradorite

The problem with working in a bead store is that I have no self control. After the lapis lazuli binge I went on (okay, not really a binge), I broke down and bought a whole bunch of moonstone and labradorite. Hooray!

Labradorite chips

Do you remember feldspars from the last geo-shopping post? They're the minerals that crystallize in magma and make up around 60% of the Earth's crust. Labradorite is another feldspar, (Ca,Na)(Al,Si)4O8; specifically it is a variety of anorthite. What characterizes labradorite in particular is high levels of calcium compared to sodium; specifically, labradorite contains anywhere from 50% to 70% calcium, and 30% to 50% sodium. It's named for the location of its first find, the Labrador peninsula in Canada. It can be found all over the world, from South America to Europe to Australia.

At first glance, it's kind of a dull gray rock. What makes labradorite interesting is the colorful sheen (called "schiller" or "labradoresence") it picks up when light hits it at just the right angle. Schiller is caused by the play of light against lattice distortions of high- and low-levels of calcium plagioclase phases. The light gets bounced around different layers and lattices like a ping pong ball, and the result of all that reflection and refraction is a rainbow shimmer.

Before labradorite was labradorite, it was known to the Eskimo Inuit and the Innu as "fire stone." They used a powdered form as a health tonic; it was also heavily associated with the aurora borealis. The stone was "discovered" by Europeans in the 1770s and it's been called labradorite ever since.

Because of labradorite's schiller, I think labradorite is a gem best left to be featured on its own. Matching it with other stones can be tough.

labradorite pi bracelet
Pi Bracelet in Labradorite

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