Smoky Quartz
Silicon dioxide (SiO2)
The smoky brown to gray variety of quartz, colored by natural irradiation, valued as both a gemstone and crystal specimen.
- Mohs hardness
- 7
- Color
- Light smoky gray to brown and near-black
- Type
- crystal
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Overview
Smoky Quartz is the gray-brown to nearly black variety of crystalline quartz. Its color arises from natural irradiation acting on trace aluminium within the crystal, creating color centers rather than a metallic impurity. The very dark, almost opaque form is called morion, while the Scottish variety is known as cairngorm.
It forms well-defined hexagonal prisms and points, making it popular both as a faceted gemstone and as a natural crystal specimen. Smoky quartz shares quartz's hardness of 7 and excellent durability.
Some commercial smoky quartz is produced by artificially irradiating clear quartz, which yields similar color.
Formation & geology
Smoky Quartz crystallizes from silica-rich solutions in granites, pegmatites, hydrothermal veins and alpine cavities. The smoky color develops when natural radiation from surrounding radioactive elements (such as in granite) irradiates quartz containing trace aluminium, producing color centers over geologic time.
Because it is associated with granitic rocks, it is common in many mountainous and pegmatite regions. Notable sources include the Swiss Alps, Scotland (Cairngorm Mountains), Brazil, Madagascar, Colorado and the Pikes Peak region of the USA.
How to identify it
Smoky Quartz is transparent to translucent, smoky gray to brown or black, often as hexagonal prisms with pyramidal terminations. Hardness is 7 (scratches glass and steel), with no cleavage, a conchoidal fracture and a white streak.
Look-alikes: Smoky topaz is actually a trade misnomer often referring to smoky quartz; true topaz is harder (8), denser and has cleavage. Andradite and dark tourmaline differ in crystal habit. Heavily irradiated clear quartz can mimic natural smoky color. The combination of hexagonal habit, hardness 7 and brown transparency identifies smoky quartz.
Uses & significance
Smoky Quartz is used as an affordable faceted gemstone in rings, pendants and earrings, and is highly popular as natural points, clusters and carvings among crystal collectors. Scottish cairngorm has traditional use in Highland jewelry and kilt pins.
Its durability and large clean crystals make it suitable for big statement gems. Color ranges from delicate champagne smoky to deep morion black.
Metaphysically it is regarded as a grounding and protective stone associated with the root chakra, though these claims are not scientifically supported.
Frequently asked questions
What makes smoky quartz brown?
Natural radiation acting on trace aluminium in the quartz creates color centers that give the smoky brown-to-black hue; no metallic dye is involved.
Is smoky quartz irradiated and is it safe?
The color comes from past natural irradiation and the finished stone is not radioactive; commercially irradiated smoky quartz is also safe to handle and wear.
Is smoky quartz the same as smoky topaz?
No. Smoky topaz is usually a misleading trade name for smoky quartz; true topaz is a different, harder and denser mineral.
Can smoky quartz fade?
Yes, prolonged exposure to strong sunlight or heat can lighten or remove the smoky color over time, so avoid extended direct sun.
Smoky Quartz identified by the community
Real specimens identified with Rock Identifier.
