Onyx is a mineral like marble or granite. It is a form of chalcedony, and as such is part of the quartz group. Like the other stones in the chalcedony family, this material has a smooth, waxy luster. It can be found in a wide range of colors (white, reddish brown, brown and banded), often in contrasting layers. You often see the mineral in black and white parallel layers or in brown and white layers called sardonyx. You can see such layering in the armadillo fetish below that is carved by Abby Quam and Clayton Panteah.
Because the mineral reads a 6.5 on the Mohs scale of hardness onyx is a very good stone for use in carving.
According to jewelrynotes.com you can only find this mineral in three places: Mexico, Arizona and Algeria. In Mexico, it is mined in Chihuahua, Puebla and Oaxaca. Arizona mines are in Prescott, Mayer and Ash Fork. Algeria has one mine, and it is located in Ain Tekbalet. That makes this mineral a local material and one that you will definitely want to add to your collection.