Black onyx belongs to the group of chalcedony, a silicate stone. This stone looks like a dark black crystal with opaque transparency and waxy texture all over the stone. Finding a real black onyx is extremely rare, so most black onyx are prepared by heating and polishing the stone. Natural black onyx is always characterized by its rough texture with perpendicular lines all over the gemstone. This stone is associated with root chakra which is responsible for grounding and spiritual balancing.