Smoky Quartz
Quartz var. Smoky Quartz (IMA-approved: Quartz) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal symmetry; typically appears as hexagonal-shaped prismatic crystals capped by pyramidal terminations
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with color resulting from natural irradiation of aluminum-bearing quartz
Formation Process
Igneous/Hydrothermal: Forms through the slow crystallization of silica-rich magma or hydrothermal fluids. The brown/grey color is caused by natural gamma radiation from surrounding rocks acting on aluminum impurities within the crystal structure.
About This Crystal
A translucent to nearly opaque variety of quartz. It exhibits a vitreous (glassy) luster and ranges from a pale yellowish-brown to a deep, dark 'morion' black. This specimen shows a rough prismatic habit with visible pyramidal faces and a fractured base.
Physical Characteristics
Color: Smoky grey, brown, to black; Streak: White; Cleavage: None (poor/indistinct); Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually none; Tenacity: Brittle.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009 (uniaxial positive); Pleochroism: Weak to distinct dichroism in shades of brown/grey.
Hardness & Durability
Origin Region
Prominent sources include Brazil, Switzerland (The Alps), Madagascar, Scotland (Cairngorm), and the USA (Colorado). Commonly found in pegmatites and granitic rocks.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; very durable for most jewelry applications, though can chip if struck hard.
Care & Maintenance
Cleans safely with warm soapy water. Avoid steam cleaning or ultrasonic cleaners if the stone has significant internal fractures. Do not expose to prolonged intense sunlight or high heat, as the color can fade or turn yellowish.
Rarity & Value
Common; relatively inexpensive. Value increases with transparency, size, and depth of color. Darker 'Morion' and 'Cairngorm' varieties are highly sought after by collectors. Irradiation of clear quartz is common to produce synthetic smoky quartz.
Special Characteristics
May contain rutilated inclusions (Rutilated Quartz) or internal phantoms. Exhibits piezoelectricity (generates electric charge under mechanical stress) and pyroelectricity.
Lore & History
Historically used in Scotland for 'Cairngorm' jewelry and in 12th-century China to make the first sunglasses. Traditionally associated with grounding, protection from negative energy, and the Root Chakra in crystal healing lore.