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A brown to black variety of quartz.

Smoky quartz – Tectosilicate minerals, quartz variety – SiO₂ – 04.DA.05 – 75.01.03.01 – Α-quartz: trigonal trapezohedral class 3 2 – Β-quartz: hexagonal 622 – Trigonal 32 – A = 4.9133 Å, c = 5.4053 Å; Z=3 – Brown, gray, black – 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive – Common Dauphine law, Brazil law and Japan law – {0110} none – Conchoidal – Brittle – 7 – lower in impure varieties (defining mineral) – Vitreous – waxy to dull when massive – White – Transparent to nearly opaque – 2.65; variable 2.59–2.63 in impure varieties – Uniaxial (+) – N_ω = 1.543–1.545 – N_ε = 1.552–1.554 – +0.009 (B-G interval) – Weak, from red-brown to yellow-brown – 1670 °C (β tridymite) 1713 °C (β cristobalite) – Insoluble at STP; 1 ppm_mass at 400 °C and 500 lb/in² to 2600 ppm_mass at 500 °C and 1500 lb/in² – Hexagonal, Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic).