Spodumene

Spodumene is a pyroxene mineral consisting of lithium aluminum silicate - LiAl(SiO₃)₂ - and is a source of lithium. It occurs as colourless to yellowish (triphane), purplish or lilac (kunzite), yellowish-green, or emerald-green (hiddenite) prismatic crystals, often of great size.

Crystals form in the monoclinic system and are typically heavily striated parallel to the principal axis. Crystal faces are often etched and pitted with triangular markings.

Spodumene is derived from the Greek, meaning "burnt to ashes," owing to the opaque, ash-grey appearance of material refined for use in industry. Transparent material has long been used as a gemstone with varieties kunzite and hiddenite noted for their strong pleochroism. Source localities include Brazil, Madagascar, USA (North Carolina, California), Afghanistan, and Pakistan.

Physical and optical properties

Physical properties

• Hardness: 7
• Cleavage: Perfect prismatic, two directions at nearly 90°
• Fracture: Sub-conchoidal
• Specific gravity: 3.17-3.19

Optical properties

• RI: 1.66-1.68
• Birefringence: 0.015
• Dispersion: 0.017 (low)
• Lustre: Vitreous
• Transparency: Usu. transparent
• Pleochroism: Strong in Kunzite: pink, colourless; hiddenite: yellow-green, blue-green
• Luminescence: Kunzite often fluoresces orange to red under LW UV
• Phenomena: Tenebrescence, chatoyancy

References

• Webster, R. (2000). Gems: Their sources, descriptions and identification (5th ed.), pp. 186-190. Great Britain: Butterworth-Heinemann.

See also: List of minerals