Decorative Items
Black onyx's characteristic bands make it an aesthetically pleasing carving material for cameos. The ancient Romans and Grecians highly favored onyx for its aesthetic appeal. Cameos displayed black backgrounds with white reliefs that depicted prominent figures. Black onyx chips and scratches easily, as is suggested by its name, which means "fingernail" in Greek. The ancient Romans also used black onyx for carving stamps and seals.
Household Items
Useful items such as bowls, urns, vases, mortar and pestles and lamps are carved from black onyx. Bowls and other pottery items were predominantly sculpted from black onyx in ancient Greece.
Jewelry
Black onyx can be used to produced elegant jewelry items such as bracelets, earrings and rings. Many male insignia rings are carved from black onyx. Black is a masculine color, making black onyx a popular gemstone amongst men. Black onyx is the birthstone of the month of August and is associated with the astrological sign of Leo. It is not an uncommon practice for jewelers to soak black onyx in sugar-sulfuric treatments to darken its appearance. Often, black onyx is soaked in a sugary concentration for approximately a month and then washed with sulfuric acid, according to the Gem Rocks website.
Healing
In addition to its practical uses, black onyx is said to produce positive spiritual and physiological effects for the wearer. Alternative medicine enthusiasts value black onyx as a powerful amulet that redirects disruptions of the energy body and produces good fortune. Black onyx is said to promote concentration and keep one grounded. It also is said to aid in the breaking of bad habits and assist those overcoming harmful addictions.