Onyx is an attractive form of quartz that comes in a diversity of colours. It is particularly comparable with Agate, which is another kind of quartz. Onyx is obtainable in several shapes and dimensions. It is a reasonably tough stone and has solidity based on Moh’s stability scale of 7.0.
Since black gemstones can make elegant jewellery, black onyx has become very popular. There are actually relatively few gemstones that occur in black. Onyx is the most common and least expensive of all black gemstones