Onyx: meaning, properties and lore

The mineral

Like other chalcedony, onyx is silica, with the chemical formula SiO2, and it rates 7 on the Mohs hardness scale. Chalcedony is microcrystalline or cryptocrystalline quartz. Encyclopaedia Britannica describes onyx as a banded agate in which the bands appear as straight lines in cross section.⁵¹²³⁴

Onyx has the same properties as quartz, according to Encyclopaedia Britannica. The Gemological Institute of America, known as GIA, rates onyx at 7 on the Mohs hardness scale and notes that it has good toughness.¹²³⁶⁷⁴

Layered contrast makes onyx useful for carved cameos and intaglios. Carnelian onyx has white and red bands, and sardonyx has white and brown bands, according to Encyclopaedia Britannica. Both are named as onyx varieties.¹

Sardonyx is a stone compounded of sard and onyx, with its substance formed in layers of differing colours. A sardonyx may look like a one-coloured mass until it is carved.³⁸

What many call black onyx is actually dyed black chalcedony, according to GIA. Natural black chalcedony is rare, so virtually all black chalcedony is treated. Black onyx has a smooth, opaque appearance and deep black colour, with a matte to semi-gloss finish.²⁶

History and lore

The Romans used the name onyx for a variety of stones, including alabaster, chalcedony and what is now known as onyx marble, according to Encyclopaedia Britannica. The name was therefore applied more widely in antiquity than it is today.¹

Onyx is one of the 12 stones mentioned in the Bible (Exodus 28:20; 39:13) as adorning the breastplate of Yahweh's high priests, according to Encyclopaedia Britannica. The Book of Job says wisdom cannot be valued with the gold of Ophir, the precious onyx, or the sapphire.¹⁸

Ancient Greeks put onyx in amulets to protect sailors from drowning, according to GIA. In ancient times sardonyx was a popular stone for Roman seals and signet rings, as hot wax would not stick to it. Roman soldiers wore sardonyx rings with the image of Mars carved on them for protection in battle.²³

Josephus identified the two stones of the Ephod as sardonyx, which he said represents the sun and the moon, according to The magic and science of jewels and stones. Dr. Emil A. Braun traced the Hebrew name Shoham to an Arabic word meaning blackness. Pliny defined sardonyx as 'candor in sarda', a white opaque layer upon a red transparent stratum of the true red sard.⁹

Philostratus, biographer of Apollonius of Tyana, recorded that Apollonius wore a gem of onyx in a ring of lead on Saturday, the day of Saturn, according to The magic and science of jewels and stones. Onyx was among the stones on which astrological zodiacal symbols were usually engraved in Greek and Roman times, according to The Curious Lore of Precious Stones. A monogram of the name of Christ was engraved on an onyx gem, illustrated in Gorlaeus's Cabinet de Pierres Antiques Gravées (Paris, 1778).⁹¹⁰

The Curious Lore of Precious Stones records that onyx, if worn on the neck, was said to cool the ardours of love. The belief that onyx provoked discord and separated lovers was commonly associated with the stone. A camel's head or two goats among myrtles engraved on an onyx was held to have the power to constrain demons, and a wearer would see terrible visions in sleep.¹⁰

Birthstone, zodiac and chakra links

Onyx is the seventh wedding anniversary gemstone, according to GIA. This is the anniversary list that GIA gives for the stone.²

Crystal practitioners say onyx is the modern modern modern zodiac stone for Leos, born between July 23 and August 23, and they also name it as the birthstone for July.

Modern crystal practitioners associate black onyx with the Root Chakra, green onyx with the Heart Chakra and white onyx with the Crown Chakra. These chakra links are a modern practitioner practice. Practitioners also associate onyx with the numerical vibration 6.

What crystal practitioners say

Believers hold that onyx is a powerful and protective stone that brings strength, focus and grounding energy. Practitioners believe it enhances physical and mental strength and boosts confidence. Crystal practitioners also believe onyx helps individuals overcome habits and addictive behaviours by supporting self-mastery and self-control.

Black onyx is said to provide grounding, strength and protection.

Onyx is said to have a strong connection with grounding and stability, and to help people connect with the Earth's energy. Practitioners traditionally believe it helps ease grief. Crystal practitioners who write about stones repeat the grief attribution with alternative claims of protection.

Onyx is believed to hold memories of what happens to the wearer and can be used for psychometry.

Metaphysical and new-age gemstone writers occasionally repeat the onyx grief attribution, often alongside contradicting claims of protection or strengthening. Crystal practitioners describe these links as contradictory among themselves.

What testing has found

Both real and fake crystal groups reported similar impressions, which suggests the placebo effect could be at play.¹¹

Pleasant feelings or seeming successes of crystal healing are attributed by Ernst to the strong placebo effect and cognitive bias among believers.¹¹

Gem cutters are warned that silicious mineral dust from quartz, including onyx, may cause silicosis and silicotuberculosis, according to the Gem Society. Researchers and tests have not been reported for this warning in the claims.⁴