Sunday, 5 June 2011

Tiger's eye and tiger iron ~

Tiger's eye and tiger iron have tiger's eye in common.  Tiger's eye is characterised by dark brown and honey-coloured stripes or bands which catch the light and seem to ripple slightly as specimens are moved in the light.  It is a pseudomorph, meaning that a mineral has moved into another form taking on the existing mineral's structure making it looks like something that it isn't.  In this instance the host structure is fibrous crocidolite and the immigrant is silica.

Tiger iron is described in Wikipedia as being "an altered rock composed chiefly of tiger's eye, red jasper, and black hematite."  This machine-shaped and polished egg is heavier than it looks!

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