Onyx is a type of Chalcedony. Onyx occurs naturally in black, but is often dyed and highly polished for a more uniform color and a sleek appearance. Other colors that claim to be Onyx are actually varieties of Calcite and Aragonite. A powerful protection stone, Onyx healing crystals absorb and transform negative energy to prevent the drain of personal energy. Onyx aids the development of emotional and physical strength and stamina, especially when support is needed during times of stress.