Smoky Quartz
Quartz var. Smoky Quartz (a silicate mineral species) · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal crystal system; typical habit is hexagonal prism terminated by two sets of rhombohedrons
Mineral Group
Silicates (specifically Tectosilicates within the Quartz group)
Chemical Formula
SiO2 (Silicon Dioxide) with traces of Aluminum (Al) and natural irradiation
Formation Process
Igneous/Hydrothermal: Crystals form from silica-rich fluids in pegmatite veins or volcanic cavities; the smoky color is induced by natural gamma radiation interacting with trace aluminum impurities in the lattice.
About This Crystal
A transparent to translucent variety of quartz displaying a distinct grayish-brown to near-black 'smoky' appearance. Luster is vitreous (glass-like) on crystal faces with uneven or conchoidal fracture visible in rough specimens.
Physical Characteristics
Color: Pale brown to deep chocolate or black; Streak: White; Cleavage: None; Fracture: Conchoidal; 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 dark varieties (brown to reddish brown).
Hardness & Durability
Origin Region
Major deposits include Brazil, Switzerland (the Alps), Scotland (Cairngorm), Colorado (USA), and Madagascar; commonly found in granitic pegmatites.
Hardness & Durability
Mohs hardness: 7; Toughness: Good (indistinct cleavage makes it durable); Stability: Excellent for jewelry, though intense direct heat may cause the color to fade.
Care & Maintenance
Safe to clean with warm soapy water and soft brushes. Avoid prolonged exposure to high heat. While stable, keep separate from harder gems like diamond or sapphire to prevent scratching.
Rarity & Value
Common; Value is determined by transparency, evenness of color, and crystal size. Darker 'Morion' varieties are highly sought after by collectors. Generally affordable with few synthetic versions marketed.
Special Characteristics
Can contain needle-like rutile inclusions (Rutilated Quartz) or phantoms. The smoky color can be artificially induced in clear quartz via lab-based irradiation.
Lore & History
Historically used in China for early sunglasses in the 12th century. In lore, it is considered a 'grounding' stone. The national gem of Scotland, known there as Cairngorm, it has long been used to adorn traditional Highland dress like daggers and kilt pins.