Onyx primarily refers to the parallel banded variety of the silicate mineral chalcedony.  The colors of its bands range from black to almost every color. Commonly, specimens of onyx contain bands of black and/or white. Onyx, as a descriptive term, has also been applied to parallel banded varieties of alabaster, marble, obsidian and opal, and misleadingly to materials with contorted banding, such as Cave Onyx and Mexican Onyx