  Orthoclase.  
Description from the source: 
Orthoclase (K Al Si3 O8 mon.), San Gotthard, Tessin, Switzerland. Geminated crystals of the variety Adular. 5x4x3 cm; 25 g. 
Source: Simone Citon 
Contributor: John Gray 
Acquired: 30 September, 2008 
Text Updated: 1 October, 2008 
Price: Trade 
Size: 2" 
Composition: KAlSi3O8
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