mineral
Iceland Spar (Optical Calcite)
Calcite (CaCO3)
Hardness of 3 on the Mohs scale, transparent to translucent, vitreous to earthy luster, rhombohedral crystal structure, perfect cleavage in three directions, specific gravity of 2.71.
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Physical properties
Hardness of 3 on the Mohs scale, transparent to translucent, vitreous to earthy luster, rhombohedral crystal structure, perfect cleavage in three directions, specific gravity of 2.71.
Formation & geological history
Formed in sedimentary, metamorphic, and igneous environments, commonly precipitated from hydrothermal solutions or calcium-rich waters in geological cavities.
Uses & applications
Used in optical and polarization instruments, polarizing microscopes, laser technology, and sought after by mineral collectors.
Geological facts
Iceland Spar exhibits strong optical birefringence (double refraction), meaning it splits light into two separate rays, creating a double-image effect when placed over text.
Field identification & locations
Easily identified by its rhombohedral cleavage shapes, perfect double refraction, and effervescence when exposed to dilute hydrochloric acid.
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