Onyx

Big Photo

Russia
3.81 carats
© Brian Kosnar - Mineral Classics

Layer stone with the combination of a black base and a white upper layer, also called true onyx or Arabic onyx. Onyx is also a name sometimes used for unicolored Chalcedony (e.g., black onyx).

The name Onyx has its origin in the Greek language and means "fingernail", probably because of its weak transparency.

Onyx Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 

Onyx Gemstones by Size

This table shows distribution of Onyx gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:3.55 cts
Heaviest:3.81 cts
Average:3.66 cts
Total photos:4
Do you have a larger Onyx? Why not upload a photo?
3.55ct to 3.58ct3.58ct to 3.60ct3.60ct to 3.63ct3.63ct to 3.65ct3.65ct to 3.68ct3.68ct to 3.71ct3.71ct to 3.73ct3.73ct to 3.76ct3.76ct to 3.78ct3.78ct to 3.81ct
General Information
A variety or type of:Agate, which is a variety of Chalcedony, which is a variety of Quartz
Photos of natural/un-cut material from mindat.org
Onyx Treatments
Black chalcedony ("onyx") is assumed to be dyed - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 7
Physical Properties of Onyx
Mohs Hardness6.5 to 7
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Specific Gravity2.55 to 2.70
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Optical Properties of Onyx
Refractive Index1.530 to 1.543
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Optical CharacterUniaxial/+
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Colour
Colour (General)Straight color bands (black with white layer)
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
TransparencyOpaque
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
More from other references
Crystallography of Onyx
Crystal SystemTrigonal
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Further Information
Mineral information:Onyx information at mindat.org
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