Onyx is a banded variety of the oxide mineral chalcedony. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved bands and onyx has parallel bands. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Commonly, specimens of onyx contain bands of black and/or white.
Gem family: Chalcedony
Cleaning Onyx Gemstones
Cleaning onyx jewelry is pretty straightforward: Just use a soft, dry cloth or a soft brush to wipe any dirt off your gemstones.
You can also use a little water to moisten the cloth and make the cleaning easier.
Don’t wet the stone or soak it in water, however, as onyx is porous and absorbs liquids easily.
After the cleaning, dry the stone with a soft cloth.