Onyx is the parallel-banded variety of chalcedony, an oxide mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands; agate has curved bands while onyx has parallel bands. The colors of its bands range from black to almost every color. Specimens of onyx commonly contain bands of black and/or white.[1] Onyx, as a descriptive term, has also been applied to parallel-banded varieties of alabaster, marble, calcite, obsidian, and opal, and misleadingly to materials with contorted banding, such as "cave onyx" and "Mexican onyx".[1][3][4]
Sardonyx is a variant in which the colored bands are sard (shades of red) rather than black. Black onyx is perhaps the most famous variety, but is not as common as onyx with colored bands. Artificial treatments have been used since ancient times to produce both the black color in "black onyx" and the reds and yellows in sardonyx. Most "black onyx" on the market is artificially colored.[7][8]
The name has also commonly been used to label other banded materials, such as banded calcite found in Mexico, India, and other places, and often carved, polished and sold. This material is much softer than true onyx, and much more readily available. The majority of carved items sold as "onyx" today are this carbonate material.[9][10]
Artificial onyx types have also been produced from common chalcedony and plain agates. The first-century naturalist Pliny the Elder described these techniques being used in Roman times.[11] Treatments for producing black and other colours include soaking or boiling chalcedony in sugar solutions, then treating with sulfuric or hydrochloric acid to carbonise sugars which had been absorbed into the top layers of the stone.[8][12] These techniques are still used, as well as other dyeing treatments, and most so-called "black onyx" sold is artificially treated.[13] In addition to dye treatments, heating and treatment with nitric acid have been used to lighten or eliminate undesirable colours.[8]
It has a long history of use for hardstone carving and jewelry, where it is usually cut as a cabochon or into beads. It has also been used for intaglio and hardstone cameo engraved gems, where the bands make the image contrast with the ground.[14] Some onyx is natural but much of the material in commerce is produced by the staining of agate.[15]
Onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items.[16] Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos.[17]
Onyx was known to the Ancient Greeks and Romans.[22] The first-century naturalist Pliny the Elder described both type of onyx and various artificial treatment techniques in his Naturalis Historia.[11]
The ancient Romans entered battle carrying amulets of sardonyx engraved with Mars, the god of war. This was believed to bestow courage in battle. In Renaissance Europe, wearing sardonyx was believed to bestow eloquence.[25] A traditional Persian belief is that it helped with epilepsy.[26] Sardonyx was traditionally used by English midwives to ease childbirth by laying it between the breasts of the mother.[27]
If Onyx sounds interesting to you, you can learn more at onyxlang.io. You can find installation instructions, getting started guides and example projects to get yourself going.As of November 2023, Onyx is still very much in a beta state, but the only way for it to get out of beta status is for more people to use and stress test it! I'm always open for feedback and pull requests!
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