Smokyquartz (SiO2) is a variety of quartz (silica), which is colored by an admixture of aluminum, sodium and lithium. It crystallizes in an arch system and has a hardness of 7 on the Mohs hardness scale. A typical crystal shape is a hexagonal prism with two arches, in which the prism surfaces are grooved horizontally. However, twinning or growth of polycrystals usually occurs, but we also encounter single crystals.
Color clear; brown in various shades up to gray; morion-black variety; coloration of Al, Li, Na impurities by natural radioactive radiation
The appearance of the crystal crystals
Density 2.65 g ⋅ cm − 3