  Ulexite.  
Description from the source: 
Ulexite (Na Ca B5 O6 (OH)6x5 H2O tric.), Boron, California, USA. When viewed parallel to the fibers, Ulexite transmits light in a similar fashion to fiber optics. 3,2x1,5x1 cm; 8 g. 
Source: Simone Citon 
Contributor: John Gray 
Acquired: 27 December, 2008 
Text Updated: 28 December, 2008 
Price: Trade 
Size: 1.25" 
Composition: NaCaB5O6(OH)6.5(H2O)
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