Chalcedony and agate
Onyx
Straight-banded chalcedony
Onyx is straight-banded chalcedony. Learn its identifying features, lookalikes, recognized sources, care, treatments, and responsible modern associations.
Material identity
At a glance
- Identity
- Agate variety
- Composition
- SiO2
- Mohs hardness
- 6.5-7
- Crystal form or structure
- Microcrystalline
- Recognized sources
- Brazil / India / Uruguay - major banded-chalcedony sources
Recognized sources provide geographic and market context. Appearance alone cannot establish the origin of an individual specimen.
Beginner identification
How to identify Onyx
Real material comparison
Reference gallery
Use these credited photographs to compare natural variation. No photograph can authenticate an unknown specimen by itself.
Lookalikes
Commonly confused with
Market context
Treatments and imitations
Observation guide
What to check
Use visual checks to ask better questions, not to replace qualified testing when identity, treatment, value, or origin is consequential.
Practical handling
Care and safety
Responsible buying
Ethics and sourcing
The material story
A short story about Onyx
References
Sources
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IMA Database of Mineral Properties — International Mineralogical Association
Official context for accepted mineral names, formulas, status, and the IMA mineral database.
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GIA Gem Treatments — Gemological Institute of America
Treatment vocabulary, disclosure, and market relevance.
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Mindat — Hudson Institute of Mineralogy
Mineral identity, localities, habits, associations, and documented specimen context.
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CIBJO Blue Books — World Jewellery Confederation
Trade terminology, treatment language, and disclosure frameworks.
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Wikimedia Commons file records — Wikimedia Foundation and individual contributors
Image provenance, authorship, license terms, and source-file records.
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