Oval black onyx cabochons, 16×11 mm, with flat back and mirror finish. The deep, uniform black of these pieces makes them stand out in any metal; they contrast especially well with 925 silver and yellow gold. Available in packs of 2 or 5 pieces.
Product Sheet
| Mineral |
Black Onyx (microcrystalline quartz chalcedony, banded black agate variety) |
| Dimensions |
16×11 mm (±0.5 mm), approximate thickness 5–6 mm |
| Shape and Back |
Calibrated oval, flat back, convex dome |
| Finish |
Mirror polish |
| Hardness |
6.5–7 Mohs — suitable for rings and pendants; we recommend a closed bezel setting for greater edge protection |
| Origin |
Material purchased at a wholesale lapidary market |
| Treatment |
No detectable treatment. Commercial black onyx may receive thermal staining; these pieces show no signs of treatment under lapidary inspection. |
| Piece Type |
Available in a pack of 2 pieces or a pack of 5 pieces |
These specific pieces
The black of the onyx in this lot is dense and uniform, without gray areas or spots. The mirror polish produces a clean reflection that allows the setting metal to reflect on the stone's surface, which is particularly striking in polished silver or yellow gold.
At 16×11 mm, this size is a classic in silver jewelry: large enough to be seen from a distance, compact enough not to dominate the hand. Ideal for signet rings, understated pendants, and drop earrings in architectural or minimalist inspired designs.
How black onyx forms
Onyx is a variety of agate (microcrystalline quartz) formed by parallel layers of silica precipitated in rock cavities.
What mounting it works for
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Bezel setting (925 silver or other precious metals) — the calibrated 16×11 mm size allows for the use of standard oval bezel templates available from jewelry supply vendors; it facilitates series reproduction.
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Signet or statement ring in 925 silver — the deep black and medium size make this stone the natural choice for understated, high-impact designs. It combines well with hammered or textured silver surfaces.
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Wire wrap — the flat back facilitates perimeter wrapping; an oxidized black wire or silver design reinforces the stone's dark character.
Black onyx in lapidary tradition
Black onyx was used in Ancient Rome for seals, cameos, and signet rings, where its polished surface allowed for clear engraving of initials. In the Art Deco period (1920s–1930s) it was one of the most used minerals in jewelry, combined with diamonds and platinum to create maximum color contrasts.
The symbolic properties attributed to minerals belong to cultural and historical traditions. They are shared for educational purposes, not as medical advice or a substitute for professional care.
How to recognize genuine black onyx
Genuine black onyx has a slight translucency under intense light (direct LED on the edge of the piece), unlike black glass which is completely opaque. Its hardness of 6.5–7 Mohs makes it resistant to scratching with a coin.
Frequently Asked Questions
Is the black color completely natural?
No detectable treatment under lapidary inspection. Commercial black onyx may have received staining or thermal treatment at the source; these pieces show no signs of this. Statement based on observation; the piece does not include formal gemological certification.
Are they suitable for paired earrings?
Yes. As they are calibrated pieces (16×11 mm), all units in this lot have the same nominal dimensions, making them suitable for symmetrical earrings without the need for manual pairing.
Which pack should I choose, 2 or 5 pieces?
The 2-piece pack is ideal for a pair of earrings or a ring + pendant set. The 5-piece pack allows for a project with several pieces or to have spare parts for future work.
Are the dimensions exact?
16×11 mm with a tolerance of ±0.5 mm. These are standard industrial stock pieces, with greater dimensional uniformity than free-form cabochons.
How to care for black onyx?
Clean with a damp microfiber cloth. Avoid acidic solutions or abrasives. For jewelry with onyx in a setting, consult our jewelry care guide.
See also: all cabochons · stone collection.
