Stone Explorer Onyx

Onyx, names and layers.

Separate banded onyx, sardonyx and commercial black chalcedony. Look at the layers, examine colour treatment and distinguish carbonate stone sold under the same name.

In our shop: all onyx pieces →

Two records

Two ways in · pick one

Each specimen opens its own file.

How to read the wall

One name, several materials.

A photograph can show layers and colour. It cannot establish whether a black colour is natural or applied, or which material carries the name.

Bands

Straight layers

Onyx names chalcedony whose layers run straight and roughly parallel; agate layers more often follow the wall of the cavity.

Colour

Natural or applied

Natural and applied colour can occupy the same range. A photograph alone cannot tell them apart.

Name

Two stones, one word

Onyx marble is a banded carbonate stone, a different material from silica onyx.

Sources and image credits

Every claim keeps its scope.

The references below describe onyx as a material, its names and its treatments. The photographs describe two particular pieces. None of it certifies a BE. lot.

GIA, Wedding Anniversary Gemstones, Onyx sectionMaterial reference · scope of use
Use
Straight parallel chalcedony bands; dyeing of commercial black onyx.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
Götze, Möckel & Pan (2020), Mineralogy, Geochemistry and Genesis of AgateMaterial reference · scope of use
Use
Review of banded silica formation, mineralogy and open questions; not a universal onyx deposit model.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
GIA, August birthstones, Sardonyx sectionMaterial reference · scope of use
Use
Sard/onyx colour band nomenclature and treatment boundary.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
GIA, Identifying Black Opaque Gem Materials (1996)Material reference · scope of use
Use
Laboratory identification of black opaque materials; appearance alone insufficient.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
Estonian Museum of Natural History, ELM G229:203Material reference · scope of use
Use
Catalogued onyx, Australia; collection record, not treatment analysis.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
Oxford University Museum (2012): Alabaster and travertineMaterial reference · scope of use
Use
Onyx marble as a banded carbonate stone, separate from silica onyx.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
GIA: An Introduction to Gem TreatmentsMaterial reference · scope of use
Use
Dyeing of chalcedony in many colours.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
Hart (1927), The Nomenclature of SilicaMaterial reference · scope of use
Use
Historical use of onyx, sardonyx and nicolo as silica names.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
Gliozzo (2019), Variations on the silica theme, §5.5Material reference · scope of use
Use
Onyx, sardonyx and nicolo; natural and applied colour in banded silica.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
GIA, Gems & Gemology Winter 1986Material reference · scope of use
Use
Reports virtually all so-called black onyx as treated.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
CIBJO, The Gemstone Book (2022)Material reference · scope of use
Use
Lists trade Onyx (black) as dyed (always), and black-and-white straight-layered onyx as dyed (commonly).
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
GIA, Gems & Gemology Winter 1988Material reference · scope of use
Use
A strand of beads in which some black beads were surface-coated; the coating wore at the edges and came off with acetone.
Limit
This reference does not identify or certify a BE. specimen.
Link
Open source ↗
Specimen photographsImage credits · reference specimens
Onyx · museum specimen
Tõnis Saadre / Estonian Museum of Natural History · CC BY-SA 4.0. Resized; colour and original labels preserved.
Onyx · Mainz Basin
Mhrobben · CC BY-SA 4.0. Resized; colour preserved.
Formation illustrationExplanatory model · not site data
Use
Illustrates the bounded formation pathway described in this Explorer.
Limit
The drawing is not a measured field section, microscopy image or record of a BE. product.

Questions about Stone Explorer

Which onyx records can I compare?

A catalogued onyx specimen from the Estonian Museum of Natural History and a banded onyx fragment from a sand pit in the Mainz Basin, Germany.

Can a photograph show whether onyx colour is natural?

No. Natural and applied colour can look the same in a photograph; a stone's treatment status comes from its documented record, not from its colour.

What does the onyx formation view show?

One cavity-filling example for banded silica, from an opening in the rock to a cut section through the layers.