Onyx
On the label: Onyx · Gemstone
What it is
Banded chalcedony; the solid black jewelry onyx is almost always dyed agate, which is traditional and legal when described as onyx. Mohs 6.5 to 7.
Gemstones: Natural gemstones, as mined and cut. Hardness (Mohs scale) says what scratches what; treatment (heat, oil, dye) must be disclosed under FTC rules.
In the research
6 PubMed papers mention it with jewelry, allergy, eyewear or UV; the three most recent:
- Angle-Closure Glaucoma due to Lens Subluxation Associated With Orbital Arteriovenous Malformation · Ophthalmic plastic and reconstructive surgery, 2026
- Forensic characterization of Brazilian gemstones: A pilot study employing raman spectroscopy and multivariate analysis · Forensic science international, 2025
- Biological Sunglasses in a Deep-Sea Squid: Pigment Migration in the Retina of Gonatus onyx · Vision (Basel, Switzerland), 2024
A paper is a paper, not a verdict: titles are listed so you can read them, and a study on one fabric or one filter says little about the piece in your hand.
Other gemstones
Clasp & Lens describes materials from the public record and does not appraise, grade or test pieces; what a listing states is the supplier's statement. If a piece causes a rash, take it off; a reaction that spreads or blisters is a doctor's question, and sunglasses are no substitute for impact-rated eye protection where that is required.