The black onyx used in jewelry is almost always banded agate that’s been boiled first in sugar water then in sulphuric acid. This process for altering onyx is an ancient one. In the 1930s, archaeologists began to excavate Arikmedu, a city on India’s southeast coast that dates back to the second century B.C. What they found was that Arkimedu’s chief product was beads, made of both glass and stone. Among the lapidary techniques used by these beadmakers, was the making of black onyx.
Agate is a variety of chalcedony, is a cryptocrystalline quartz. Natural agate tends to occur in colored bands. The slightly duller bands tend to be “softer” or more porous; the whiter bands, which consist of denser quartz, are less absorbent. When banded onyx is boiled in sugar water—usually at a low heat over a couple of weeks—the slightly porous bands tend to absorb the liquid. The sugar then caramelizes in them turning these bands brown. If this sugar-rich stone is then put in heated sulfuric acid, the sugar carbonizes, turning the agate black. Most of today’s black onyx originates as South American agate that’s naturally shaded grey and white and black.

Astrology: Connected with Capricorn and Saturn
Chakra: 1st (root) chakra
Metaphysically, black onyx shares the same powers as banded agate, harmonizing yin and yang energies and strengthening the ability to concentrate. It’s known as a powerful protector, said to repel negative energy and counter black magic. Black onyx is also considered useful for developing determination and steadfastness. Another belief, which has been attributed to both India and Ancient Egypt, states that black onyx may be used to cool the passions.

Black onyx is one of those stones that goes with nearly anything. It’s always striking with pearls or mother of peal. For an antique look, pair glossy black onyx beads with the red garnets or ruby. For dramatic contrast, pair it with any of the following: turquoise, carnelian, coral, cat’s eye, tiger’s eye, peridot, amber, red jasper or red aventurine. A harmonious way to use black onyx, is to string it with stones that contain black or grey streaks or veins such as: zoisite, black feldspath, snowflake obsidian, Botswana agate, and the turquoises that show black matrix. And for a gorgeous sparkly combination, string black onyx with both clear tourmalated and rutilated quartz.

Color: Black
Chemical composition: SiO2 silicon dioxide
Mohs’ hardness: 6 ½ -7
Transparency: Transparent to opaque
Luster: Vitreous to greasy
Fracture: Uneven
Crystal system: Hexagonal (trigonal); microcrystalline aggregates
Cleavage: None
Specific Gravity: 2.60-2.65
Occurrence: Generally South America