煙水晶

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.