Onyx is the variant of quartz in its microcrystalline form, which is known as Chalcedony. Its long history dates back to biblical times when it was said to grace the clothes of religious leaders. It continued to be popular throughout the ages and was used by many societies.

Hardness:  Onyx has a hardness rating of seven on the Mohs hardness scale.

Color: Onyx is a banded variety of chalcedony. The colors of its bands range from white to nearly every color.  Black onyx is the most common variety, but is does not occur as often as onyx with colored bands. Sardonyx is a variant in which the colored bands are shades of red rather than black.

Birthstone:  Onyx is the birthstone for the Zodiac sign of Leo and is the mystical birthstone for the month of December. Onyx is also often given on the 7th and 10th wedding anniversary.

Scarcity:  Onyx is fairly abundant but among all the gems that come under the onyx family, the black onyx is the most rare.  Because it is difficult to find natural occurring black onyx, synthetic processes are used to give onyx a rich black color. The current demand for black onyx is higher than its availability.

Value: Most of the value in a piece of onyx jewelry is determined by its design instead of the actual gemstone material. The exception to this rule, are large sized pieces, which tend to be much more valuable. When considering an onyx piece, it is important to study the quality of the surface: the polish should be shiny and reflective throughout the stone’s surface.

Most Common Cuts: Due to its relative hardness, onyx is a very easily carved. The most common cut is a cabochon but it is also commonly made into beads.  Less often, it has been used for intaglio and cameos with pieces that have even layers.

Chemical Formula: The chemical formula for onyx is SiO2.

Synthetic Varieties:  Artificial treatments, such as coloring and heat treatments, have been used since ancient times to produce both the black color in “black onyx” and the reds and yellows in sardonyx.  In fact, most of the black colored onyx on the market today is artificially colored.

The majority of carved items sold as onyx in today’s marketplace are actually imposters made from carbonate material.  Often these pieces are made from other banded lapidary materials, such as banded calcite found in Mexico,Pakistan, and other places. These pieces are carved and polished to look like Onyx. This material is much softer than true onyx, and much more readily available.

History:  Onyx has a long history of being made into jewelry and hand carved objects.  Onyx is referenced in the Bible at various points and mentioned adorning the garments worn by men of religious importance.  It was first used as early as the Second Dynasty in Egypt to make bowls and other pottery.  Onyx was equally popular with the early Romans. Sardonyx (the reddish brown and white variety of onyx) was highly valued in Rome, especially for wax seals, because it did not stick to the wax.

The Greeks are attributed with naming the stone.  The Greek word ‘onyx’ means nail or claw and was giving due to the mythology that surrounds the stone.  The story tells of a day when mischievous Cupid played a trick on Venus by cutting her fingernails with an arrowhead while she was slept. When he left the clippings scattered on the sand around her, the fates turned them into stone so that no part of the heavenly body would ever perish.

During the Victorian era, black onyx took the place of some of the extravagant red gemstones. Throughout the ages, Greeks continued to be leaders in producing this gemstone.  An antiquated harbor of Marmara (once owned by the Greeks), Chalcedon, is the root word from which the name ‘Chalcedony’ has been derived. It was at the harbor that great amounts of black onyx were mined and it was also sold there as Marmara was considered the hub of jewel traders. Today onyx is mined in Brazil, India, California and Uruguay.

Rumored Healing Properties: The healing powers of gems remain a controversial issue but due to its long history, onyx has developed a reputation for holding many qualities. Onyx is believed to combat negative feelings, guard one from evil and impart strength. Black onyx is said to aid in good decision-making and is accredited with healing powers. Romantically, it is said to increase intimacy between couples and bring harmony to their relationship. Onyx is said to be particularly helpful with skin ailments, healing infected wounds as well as fungal infections, inflammation and even sunburns.