| | |   Mica sheet. This is a sheet of mica, a papery thin mineral that was often used as an electrical insulator.  The term mica refers to a range of specific minerals and I don't know which one this is exactly, so the composition is just a guess.
 Source: Mark Peterson
 Contributor: Mark Peterson
 Acquired: 13 January, 2010
 Text Updated: 13 January, 2010
 Price: Donated
 Size: 3"
 Composition: (KLi2Al(Al,Si)3O10(F,OH)2
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