If you are obsessed with the black onyx stone, and if you wish to purchase a perfect Black Onyx Ring for yourself, then this guide is for you! Black onyx is one of the semi-precious gemstones that is highly valued for its deep black color, luxurious finish, and magical healing properties. Black onyx is a kind of layered chalcedony gemstone that is found with a midnight black color, having white bands on it at times. You can say that black onyx is much like agate because black onyx is a chalcedony mineral made up of microcrystalline quartz.