Smoky Quartz
Quartz var. Smoky (Silicon Dioxide) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs in hexagonal prisms with pyramidal terminations, though this specimen is massive/macrocrystalline.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (with trace Al3+ ions and natural irradiation)
Formation Process
Hydrothermal or Igneous; forms via crystallization of silica-rich fluids in pegmatites or hydrothermal veins, darkened by natural gamma radiation.
About This Crystal
A translucent to near-opaque brown-to-greyish mineral. This specimen exhibits a greasy to vitreous luster on uneven, fractured surfaces.
Physical Characteristics
Color: Smoky brown to black; Streak: White; Fracture: Conchoidal to uneven; Specific Gravity: 2.65; Fluorescence: Usually inert.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: 0.009 (uniaxial positive); Pleochroism: Weak to moderate in brown shades.
Hardness & Durability
Origin Region
Brazil, Switzerland, and USA (Colorado); common in pegmatites and granitic rocks.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; Highly stable and durable for jewelry with no cleavage concerns.
Care & Maintenance
Clean with warm soapy water; avoid prolonged exposure to intense heat which may cause color to lighten.
Rarity & Value
Common; value depends on clarity and uniformity of color. Not widely treated, though some is produced by artificial irradiation of rock crystal.
Special Characteristics
May contain rutilated inclusions or phantoms; color is caused by aluminum impurities influenced by ionizing radiation.
Lore & History
Historically used in Scotland (Cairngorm stone) for jewelry and weapons; traditionally associated with grounding and protection in folklore.