Smoky Quartz (Cairngorm)
Quartz var. Smoky Quartz · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs in hexagonal prismatic habits with pyramidal terminations or in massive, microcrystalline forms
Mineral Group
Silicates; Tectosilicate subgroup
Chemical Formula
SiO2 (Silicon Dioxide) with natural irradiation of Aluminum (Al3+) trace elements
Formation Process
Magmatic or Hydrothermal; forms through the slow cooling of silica-rich fluids in pegmatites or veins, with the smoky color resulting from natural gamma radiation from surrounding rock
About This Crystal
A translucent to nearly opaque variety of quartz ranging from light grayish-brown to deep 'morion' black. This specimen shows a vitreous to greasy luster with strong internal fracturing and possible reddish-brown hematite staining or inclusions.
Physical Characteristics
Color: Smoky brown to black; Streak: White; Cleavage: None/Indistinct; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually none/inert; Tenacity: Brittle
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
Hardness & Durability
Origin Region
Brazil, Switzerland (Alps), Scotland (Cairngorm Mountains), Madagascar, and USA (Pikes Peak, CO); found in granitic pegmatites
Hardness & Durability
Mohs Hardness: 7.0; Toughness: Fair to Good; highly durable for jewelry but sensitive to extreme thermal shock which can cause internal fractures to expand
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic cleaners if internal fractures are present. Keep away from prolonged intense heat and high-energy radiation which can cause color fading
Rarity & Value
Common; Value is driven by clarity, size, and depth of color. Natural 'Morion' (black) specimens are more highly valued by collectors; treatments like irradiation of clear quartz are common
Special Characteristics
Exhibits color-center induced pigmentation; can feature rutilated inclusions or 'phantoms' reflecting different stages of the crystal's growth history
Lore & History
Historically used in Scotland for 'sgian-dubh' (dagger) handles and jewelry. Traditionally associated with grounding, protection, and the Root Chakra in crystal healing lore; used by ancient druids as a 'power stone'.