Occurring naturally in a variety of colors, black onyx is polished to enhance appearance, a member of the quartz family.
Originally, almost all colors of chalcedony from white to dark brown and black were called onyx (SiO2 with impurities).
Physical Properties of Onyx
Onyx is a form of chalcedony, part of the quartz group. Like the other stones in the chalcedony family, onyx has a smooth, waxy luster. Onyx can be found in a wide range of colors, often layered.