Smoky Quartz
Smoky quartz is the grey-to-brown variety of quartz, coloured by natural irradiation; the darkest form is called cairngorm.
Smoky quartz is the grey-to-brown to near-black variety of quartz, coloured by natural irradiation of aluminium impurities.
About Smoky Quartzextended article
Smoky quartz is the smoky grey, brown or near-black variety of crystalline quartz. Its colour is produced by natural radiation acting on tiny amounts of aluminium in the quartz structure, which is why it is common in granites and pegmatites containing trace radioactive elements.
Identifying smoky quartz
Like all quartz it is hard (7) and forms six-sided prisms with pyramidal terminations; colour ranges from a pale smoky tint to deep brown-black (the very dark Scottish form is called cairngorm). Colour is often uneven and concentrated toward the tips. Some pale material on the market is irradiated to deepen the colour.
Where it is found
Smoky quartz is found worldwide — fine crystals come from the Swiss and Austrian Alps, Brazil, the Pikes Peak granite of Colorado (with amazonite), Scotland and many granite and pegmatite districts.
For collectors
Sharp, lustrous crystals with rich even colour and clean terminations are the most desirable, especially the classic amazonite–smoky quartz combinations.
Frequently asked questions
What is Smoky Quartz?
Smoky quartz is the grey-to-brown variety of quartz, coloured by natural irradiation; the darkest form is called cairngorm.
What is the chemical formula of Smoky Quartz?
The chemical formula of Smoky Quartz is SiO2.
What crystal system does Smoky Quartz belong to?
Smoky Quartz crystallises in the Trigonal crystal system.
Where is Smoky Quartz found?
Notable localities for Smoky Quartz include Pikes Peak, St. Gotthard Massif, Mont Blanc.
Is Smoky Quartz rare?
As a collector mineral, Smoky Quartz is generally considered common.
References & databases
Mindat.org is the world’s largest open mineralogy database. Our descriptions are written independently and fact-checked.