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Spodumene (lithium aluminum silicate)
Color: Pink, violet, cornflower-blue, green, yellow-green, yellow and colorless.
Moh’s hardness: 6-7
Refractive index: 1.655-1.68
Critical angle: 37°
Specific gravity: 3.16-3.2
Cleavage: Strongly perfect in 2 directions.
Fracture: Uneven, very splintery
Dispersion: Medium (.017)
Heat sensitivity: Moderate
Pleochroism: Trichroic - Strong (colorless to lilac to pink, and bluish-green to emerald-green to yellow-green).
Birefringence (double refraction): Medium (.015)
Crystal structure: Monoclinic
Cutting: Pre-form carefully on a saw with a new blade. Thick blades are better. Orient for best color, but away from the cleavage plane. Use no laps coarser than 600 grit. Nubond or other such laps work well. Make sure that the stone receives no shocks, otherwise at a later point in cutting, the stone may fall apart during the cutting or polishing process.
Polishing: Alumina or cerium oxide on tin/lead or tin lap at a moderately slow speed. If the cutting was done well, polishing shouldn’t present a problem.
Comments: Spodumene is a beautiful gemstone, but one must be very patient to successfully cut a stone without encountering a problem with the cleavage planes.