What Is Smoky Quartz? The Science Behind Its Color

Smoky quartz owes its brown-to-black color to natural irradiation. Trace aluminum atoms substitute for silicon within the quartz crystal lattice, and over long geological time spans, background radiation from the surrounding rock knocks an electron loose from these aluminum sites, creating a color center that absorbs light and produces the smoky tone.

The effect is entirely natural, though today it can also be reproduced artificially: clear quartz can be irradiated in a lab to produce a visually similar smoky color. Natural smoky quartz is found in granite pegmatites worldwide — notable sources include Brazil, Switzerland's Alps, and Scotland, where it's the country's national gemstone (cairngorm).