Faceted Oval Black Onyx with rose cut, available in two formats: 29×8×4 mm (no.1) and 30×8×4 mm (no.2). Intense black with a satin luster on the faceted dome and a flat, smooth back. Clean finish with no visible inclusions. For elongated pendants, statement rings, and earrings in 925 silver.
Piece Details
| Mineral |
Black Onyx (chalcedony, microcrystalline quartz) |
| Dimensions |
no.1 · 29×8×4 mm / no.2 · 30×8×4 mm |
| Shape and back |
Elongated oval, faceted dome (rose cut), flat back |
| Finish |
Mirror polished on facets and back |
| Hardness |
6.5–7 Mohs — suitable for daily wear rings with bezel setting |
| Origin |
Material acquired at wholesale market |
| Treatment |
Treated — intense and uniform black color is obtained by heating and impregnation, a standard process for market black onyx |
| Piece Type |
Available in 2 formats |
This specific selection
The black color of these cabochons is homogeneous and deep, with no tonal variations or visible inclusions.
The elongated format (approximate length/width ratio of 3.5:1) visually lengthens the finger or neck. The flat back facilitates bezel setting without the need for special adjustments.
What mounting it works for
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Bezel setting (925 silver) — the elongated format works very well in "cocktail" rings with a perimeter silver bezel. The 6.5–7 Mohs hardness makes it suitable for daily wear without the need for a closed bezel; although we recommend it to protect the dome's edge.
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Central pendant — the elongated oval profile creates an elegant vertical line pendant. Construct a 925 silver bezel with an integrated bail or use a flat back with epoxy glue for a pre-made setting.
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Wire wrap — the flat back and high hardness make it easy to work with silver wire. The intense black contrasts well with the shine of the metal.
Black onyx in jewelry tradition
Black chalcedony was used in Roman seals and cameos from the 1st century AD, and in 19th-century Victorian mourning jewelry, it was one of the most valued materials alongside jet.
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 from imitations
Black onyx is treated chalcedony: its intense and homogeneous black color is precisely the result of the standard impregnation process. Unlike black glass (cold to the touch, very dense, without cleavage) or obsidian (vitreous, conchoidal fracture), chalcedony has a microcrystalline texture and irregular fractures.
Frequently Asked Questions
Is black onyx treated?
Yes. The intense and uniform black color is obtained by heating and chemical impregnation, a standard process in the lapidary industry for chalcedony. The mineral base is chalcedony (microcrystalline quartz), whose natural color is gray or whitish.
What type of ring is this elongated format most suitable for?
The 29-30×8 mm oval is ideal for elongated solitaire or cocktail rings where a prominent black color point is desired without excessive bulk in the profile. The 6.5–7 Mohs hardness makes it suitable for daily wear with a 925 silver bezel.
What is the difference between no.1 and no.2?
Only 1 mm in length (29 vs 30 mm). The thickness is the same (4 mm). Relevant if you are working with a pre-formed bezel of exact size; if you are custom-building the bezel, both formats are practically equivalent.
Does it fit standard jewelry bezels?
Pre-formed bezels for 29×8 mm or 30×8 mm oval are not common standard formats. We recommend custom-building the bezel or using an adjustable oval chaton base. The jeweler adapts the bezel to the piece, not the other way around.
What is the possible variation in dimensions?
The declared measurements are factory measurements. There may be a variation of ±0.5 mm in any dimension as these are pieces of natural material worked by hand.
How do I care for black onyx in jewelry?
Clean with a soft, slightly damp cloth; avoid harsh chemicals, prolonged ultrasound, and exposure to intense heat. Store separately from harder gemstones. More information in our jewelry care guide.
See also: cabochons for jewelry · handmade rings · pendants.
