Onyx is a layered variety of chalcedony, making it easy to confuse with agate. The defining distinction is that onyx has flat or parallel bands while those in agate are curved. Onyx also generally has bands of black and white. Being chalcedony, it is a member of the quartz family.
The flat bands in onyx make it an ideal medium for relief carving and cameos. An excellent example of this is the Gemma Augustea, carved in 9-12 C.E. (A.D.), where the layers are used to represent foreground and background.
Black onyx is effectively just black chalcedony, and it is actually fairly uncommon naturally. Most commercially-available black onyx has been dyed to achieve this uniform black color.
Location: Onyx can come from many places, but some of the more common sources include Canada, Argentina, Australia, Botswana, Brazil, China, Czech Republic, Germany, Great Britain, India, Madagascar, Myanmar (Burma), Sri Lanka, Uruguay, and the United States.
Properties: Onyx is a stone of persistence, focus, and memory, making it an excellent stone for learning, especially those concepts which are challenging to the student. It is also helpful to anyone in a field requiring discipline and attention to detail. Another property of onyx is that it enables the retention of physical energy, giving it a rejuvenating quality. This makes it helpful to carry after a period of illness or during a demanding project. These properties combined make it excellent for those doing physical or athletic training. It also has the tendency to cool and ‘condense’ energies, bringing hyperactivity, nervousness, anxiety, anger, and irritation down to a manageable level, converting the excess into stored, usable energy. It can redirect these emotional energies into physical energy, reversing the common pattern of exhaustion that accompanies high emotional excitation. This means it can help with self-control and grief management as well. The white in banded onyx activates higher chakras (particularly the crown chakra) and heightens connectedness to divine energies, and the black parts activate lower chakras (especially the root chakra) and aid in grounding. This makes onyx a great stone for mediation and balancing apparent opposites.
Some people have used onyx to help treat bone marrow, soft tissue, and foot disorders.