Smoky Quartz
Silicon Dioxide var. Smoky Quartz · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs as macrocrystalline hexagonal prisms with pyramidal terminations; the specimen shown is a broken or water-worn raw fragment.
Mineral Group
Silicates (Tectosilicates); Quartz group
Chemical Formula
SiO2 (Silicon Dioxide) with natural irradiation of aluminum impurities (Al3+)
Formation Process
Igneous and Metamorphic. It primarily forms in pegmatites and hydrothermal veins. The smoky color is produced when silicon dioxide is subjected to natural radiation from surrounding rocks, which activates aluminum impurities.
About This Crystal
A translucent to nearly opaque dark brown or grayish-black mineral fragment. It exhibits a vitreous to greasy luster on its fractured surfaces. The specimen appears to have a rough, lighter-colored weathered exterior or matrix on the bottom with a dark, glassy interior.
Physical Characteristics
Color: Smoky brown to black; Streak: White; Cleavage: None (poor/indistinct); Fracture: Conchoidal (shell-like) to uneven; Specific Gravity: 2.65; Tenacity: Brittle; Fluorescence: Generally inert.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009 (uniaxial positive); Pleochroism: Weak to distinct in dichroic shades of brown and reddish-brown; Diaphaneity: Translucent.
Hardness & Durability
Origin Region
Found globally; notable sources include the Swiss Alps, Brazil, Scotland (Cairngorm), and the United States (mountains of Colorado and New Hampshire).
Hardness & Durability
Mohs Hardness: 7.0 (shares hardness with standard quartz); Toughness: Good (no cleavage planes); Stability: Generally stable but can fade if exposed to extreme heat or prolonged direct sunlight.
Care & Maintenance
Safe to clean with warm soapy water and a soft brush. Avoid ultrasonic or steam cleaners if the stone has significant inclusions. Store separately from softer stones like fluorite or calcite to prevent scratching them.
Rarity & Value
Common and widely available. Value is determined by transparency, intensity of color (deep uniform brown is preferred), and size. Deeply colored specimens are sometimes called 'Morion'.
Special Characteristics
The smoky color is unique in that it is caused by the ionization of aluminum atoms within the crystal lattice, a process that can be reversed by heating the stone to approximately 200-300°C.
Lore & History
Historically used in Scotland for 'Cairngorm' jewelry and in 12th-century China for the first known sunglasses made of flat smoky quartz panes. In metaphysical traditions, it is considered a 'grounding' stone, traditionally associated with the Root Chakra and believed to assist in neutralizing negative energy.