Smoky Quartz
Quartz var. Smoky Quartz (α-Quartz) · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by two rhombohedrons, often in a prismatic or massive habit.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide with aluminum impurities and natural irradiation)
Formation Process
Igneous and Hydrothermal: forms through the crystallization of silica-rich fluids. The dark color is caused by natural gamma radiation from surrounding rocks acting on aluminum impurities within the crystal lattice.
About This Crystal
A translucent to transparent brownish-grey to nearly black variety of quartz. It exhibits a vitreous luster and frequently contains internal fractures or 'veils'. This specific specimen shows a rough, prismatic fragment shape with visible dark saturation.
Physical Characteristics
Color: Smoke grey to chocolate brown; Streak: White; Cleavage: None; Fracture: Conchoidal (shell-like); Specific Gravity: 2.65; Fluorescence: Usually inert/none; Piezoelectric properties present.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: +0.009 (Uniaxial positive); Pleochroism: Weak to moderate in darker stones (brownish-grey to reddish-brown).
Hardness & Durability
Origin Region
Brazil (Minas Gerais), USA (Colorado), Switzerland (Alps), and Madagascar; found in granitic pegmatites and hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7.0; Toughness: Good; Stability: Stable, but may fade if exposed to extreme heat (over 200°C–300°C). Excellent for all jewelry types.
Care & Maintenance
Safe to clean with warm soapy water and soft brushes. Ultrasonic and steam cleaning are generally safe unless the stone has significant internal fractures. Avoid prolonged exposure to intense, direct sunlight which may cause fading over decades.
Rarity & Value
Common and affordable. Value is determined by transparency and the absence of eye-visible inclusions. Darker 'Morion' varieties or crystals with aesthetic terminations are more valuable to collectors.
Special Characteristics
May contain 'phantom' growth layers or rutilated inclusions. Extremely dark, opaque specimens are known as 'Morion'. This specimen appears to be a natural broken crystal point.
Lore & History
Historically used in China for the earliest sunglasses in the 12th century. In lore, it is considered a 'grounding stone' associated with the Root Chakra, believed to neutralize negative energy and provide emotional stability.