Onyx

Onyx Crystals

Onyx is a banded variety of chalcedony (microcrystalline quartz, SiO2) with a Mohs hardness of 6.5-7. True onyx features parallel bands of alternating color — most commonly black and white — though the term is widely used in the gem trade to refer to solid black chalcedony. Significant sources include Brazil, India, Uruguay, and Madagascar.

Onyx has been carved and polished since antiquity. The Romans used it for intaglio seals and cameos, taking advantage of its distinct banding. The name derives from Greek onux meaning "claw" or "fingernail," referencing the stone's banded, nail-like layers. Collectors today appreciate onyx for its deep, saturated black color and excellent ability to take a high polish.

This collection features polished spheres, bowls, freeforms, bracelets, tumbled stones, palm stones, and carved decorative pieces. Onyx pairs strikingly with white minerals like selenite and clear quartz. Browse our crystal home decor for more statement pieces. Free shipping on all U.S. orders over $150.

Frequently Asked Questions

What is onyx?

Onyx is a banded variety of chalcedony (microcrystalline quartz) with parallel alternating layers. The term is most commonly associated with solid black chalcedony, though true onyx has both black and white bands. Mohs hardness is 6.5-7, making it one of the more durable decorative stones.

Is black onyx real or dyed?

Both exist on the market. Much commercially available solid black onyx is chalcedony that has been heat-treated or dyed to achieve uniform black color — this is an industry-standard treatment disclosed in the gem trade. Natural banded onyx (black and white layers) is genuine and undyed. At Crystals.com, we accurately describe all treatments applied to our specimens.

What is the difference between onyx and obsidian?

Onyx is a cryptocrystalline mineral (chalcedony/quartz family) with a Mohs hardness of 6.5-7. Obsidian is volcanic glass (amorphous) with a Mohs hardness of 5-5.5. Onyx has a waxy luster and banded structure; obsidian has a glassy, conchoidal fracture. They are completely different materials that happen to share a black color.

How do I care for onyx?

Onyx is relatively durable (Mohs 6.5-7) and requires minimal care. Wipe with a soft damp cloth. Avoid harsh chemicals and ultrasonic cleaners. Dyed onyx may fade slightly with prolonged sun exposure. Store polished pieces separately to prevent surface scratches.

What is onyx used for?

Onyx has been used for carved bowls, bookends, display pieces, jewelry, and architectural accents for thousands of years. Its dense black color and ability to take a mirror polish make it a versatile design material. Onyx bracelets are popular for their sleek, neutral look that works with any outfit.