Back to Materials Onyx Onyx is a type of quartz (silicon dioxide). Its structure is made from the tiniest crystals (a condition called cryptocrystalline). Its colour can be almost anything although black and banded coloured onyx are the most common varieties. Onyx is made up of bands, and even though most people think of onyx as black, the larger pieces of rock that onyx is mined from has hundreds of bands of different chemical quartz which gives each layer its colour. The onyx we use is a black variety without banding. This is because the beads are small enough to be from singular bands. Onyx polishes to a very high level and so adds quality and finese to our pieces of jewellery. Onyx has a specific gravity of around 2.6 (2.6 times the weight of water by volume) and its hardness is 7 on the mohs scale which matches the hardness scale of most quartz types.