Optical Calcite, aka Iceland Spar excellent quality Raw Crystals are also available as Wholesale Country of origin: Mexico Size 1 to 3 inches Weight: 1 to 3 oz Origin: Mexico These natural calcite crystals have near perfect cleavage in rhombohedral shape with translucent to transparent appearance. NOTE: A pound will include approximately 4-7 chunks. If you need specifically smaller or larger chunks please send a note. Scientific facts: Calcites are relatively soft mineral, with a Mohs hardness of 3. Calcites are calcium carbonate mineral lack of light-scattering impurities within the crystals. The optical calcite in particular known for light transmission and the characteristic double refraction that makes it useful for plenty of scientific applications such as polarizing filters and microscopes. Metaphysical properties: In the metaphysical world, the Optical Calcites are believed to help promoting mental and spiritual clarity and clear blockages and transmute negative energy.