Monday, August 15, 2011

Peridot - Part Four: The Universe Makes Stained Glass Windows

Some of the most beautiful meteorites in the world (and out of the world) belong to the pallasite class of meteorites.  Many pallasites can be recognized immediately by their characteristic crystals of greenish olivine embedded in an iron/nickel matrix.  When these meteorites are cut into thin slices, light can shine through the translucent olivine, creating stunning lattices of metal and gemstone.

The example at left is the meteorite Esquel.  Gorgeous gem quality olvine, known as peridot of course, is liberally strewn through a shiny metal frame.  It seems so perfect, one might think it was manufactured.  But these incredible rocks formed naturally, far away from Earth.

The meteorite Imalac is also a pallasite, with a higher density of olivine to metal, although the olivine is of a more golden hue, and seems less gem-quality.  Some pallasites are almost all metal, while others are predominently olivine.  Each is unique, its own version of a glittering mineral 'window.'  It once was thought that pallasites must come from the interior of an asteroid-like body - the place where the olivine mantle met the iron/nickel core.  But recent studies have indicated that things are not so straightforward.  Pallasites are a glorious mystery.

This gemstone gives us an immediate connection to the heavens.  Something as simply beautiful as peridot is found in abundance in the mantle of the Earth, and is one of the most basic minerals in space rocks, too.  Of course, the Earth is really just a big space rock, itself.

Image Credits: Slice of Esquel meteorite, from flikr via Creative Commons, CC 2.0, Bistrosavage. Closeup of Imilac meteorite, original image from flikr via Creative Commons, CC 2.0, aakova.

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