Black Onyx is a luxurious chalcedony quartz with a fine texture and deep black colour. Natural black onyx is rare. Most black onyx used in jewellery today is produced by soaking agate in sugar solution and then heating in sulphuric acid to carbonise the sugar particles.
Onyx was very popular with the ancient Greeks and Romans. The name comes from the Greek word "onux", which means fingernail.
The legend behind the name goes something like this.
One day a playful Cupid cut the divine fingernails of Venus with an arrowhead while she was sleeping. He left the clippings scattered on the sand and the fates turned them into stone so that no part of the heavenly body would ever perish. True, black isn't normally the colour one associates with fingernails but then Venus may have been a closet "Goth". However, in Greek times, almost all colours of chalcedony from ivory/white to dark brown and black were called onyx. Later, the Romans narrowed the term to refer to black and dark brown colours only.
This gemstone is reputed to eliminate negative thinking and to sharpen the wits of the wearer. Onyx is said to bring spiritual inspiration. It is a great assistance in holding emotions and passions under control.