Smoky Quartz — Tumbled

Smoky Quartz is a variety of quartz (SiO₂) whose color — which varies from light brown to dark gray, reaching almost black tones — results from natural exposure to gamma radiation from radioactive elements present in the surrounding rocks, such as uranium and thorium, which generate defects in the quartz crystal lattice associated with color centers involving aluminum and hydrogen ions. It forms in granitic pegmatites and hydrothermal veins, in the same environments as hyaline quartz. The mechanical rolling process progressively rounds the ends and corners of the pieces, resulting in a smoothed external profile that preserves the internal crystalline structure. Hardness: 7 on the Mohs scale. Density: 2.65 g/cm³. Crystalline system: trigonal. Available variations, approximate data: Size: up to 3 cm Unit weight: up to 6 g (approx.) Average: 170 pieces per kg (approx.)