Smoky Quartz
Quartz var. Smoky Quartz (IMA-approved name: Quartz) · Semi-Precious Gemstone
Crystal System
Trigonal (Hexagonal system). In its raw form it exhibits a hexagonal prismatic habit; here it is seen as a smooth, rounded 'tumbled' stone.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (Silicon Dioxide). The smoky color is caused by natural or artificial irradiation of aluminum-bearing quartz.
Formation Process
Igneous/Hydrothermal. It forms in pegmatites and hydrothermal veins through the crystallization of silica-rich fluids. The color develops post-crystallization due to gamma radiation from surrounding rocks.
About This Crystal
A transparent to translucent stone with a 'smoky' brown to grayish-black color. This specific tumbled specimen exhibits a vitreous luster, smooth polished surface, and internal fractures or 'veils' that produce slight iris or rainbow reflections.
Physical Characteristics
Color: Smoky brown; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Tenacity: Brittle; Fluorescence: Generally inert.
Optical Properties
Uniaxial positive; Refractive Index: 1.544–1.553; Birefringence: 0.009; Pleochroism: Weak to moderate in darker stones (brown/red-brown). This specimen shows double refraction.
Hardness & Durability
Origin Region
Brazil, Switzerland (Cairngorm Mountains), Madagascar, and the United States (Colorado). Typically found in igneous pegmatites and metamorphic rocks.
Hardness & Durability
Mohs hardness: 7. It is very durable and has no cleavage, making it excellent for daily wear in jewelry. It is tougher than glass but can chip upon heavy impact.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if the stone has significant internal fractures. Stable under most conditions, though extreme heat may cause color fading.
Rarity & Value
Common. Value is determined by clarity and color depth. Heavily saturated, 'clean' stones are more desirable. Artificial irradiation of clear quartz is a common industry treatment to create dark smoky quartz.
Special Characteristics
Internal fractures in this specimen create a minor iris effect (rainbows). Darker varieties are sometimes called 'Morion'. It exhibits piezoelectric and pyroelectric properties.
Lore & History
Historically used in China for the first sunglass lenses in the 12th century. In Scottish lore, it is known as 'Cairngorm' and is a traditional ornament for highland dress. Metaphysically, it is associated with the Root Chakra and believed to be a grounding and protective stone.