Onyx
Black onyx is the most-worn black stone in jewellery, and nearly all of it is dyed. This is not a scandal — the practice is older than the Roman Empire — but you should know it, because a seller who won't say it is hiding something ordinary for no good reason.
What is onyx, really?
Onyx is a banded variety of chalcedony, which is quartz in microscopic fibrous form. Strictly, onyx means the straight-banded material; the solid black stone everyone calls onyx is chalcedony that has been dyed and heat-set to an even, opaque black.
The process is genuinely ancient: soak the porous stone in a sugar solution, then treat with acid, which carbonises the sugar inside the pores. The black is permanent, goes right through, and will not wash or wear out. Roman carvers were doing it two millennia ago.
Are green and red onyx real onyx?
Both are dyed chalcedony too, and both are common and legitimate. Green onyx in particular is often confused with jade or aventurine and is neither. What you are buying in all three cases is well-made, evenly coloured chalcedony — a good, hard, stable stone, priced accordingly.
Why does onyx pair so well with silver?
Black onyx has no internal life to speak of: no fire, no sparkle, no depth. That is the point. It reads as an absolute — a flat void that makes polished silver look brighter by contrast. It is why signet rings have used it for centuries and why it still looks correct with a suit.
It also takes engraving beautifully. Even, dense, fine-grained material carves cleanly and holds a crisp edge, which is why intaglio seals were cut in it long before anyone wore it for fashion.
Is onyx durable enough for daily wear?
Mohs 6.5 to 7 — quartz-family hardness, genuinely suitable for a ring worn every day. It is more prone to chipping at sharp edges than to scratching across a face, so a bezel or a flush signet setting protects it better than claws.
How do you care for onyx?
Warm water, mild soap, soft cloth. Avoid harsh solvents, bleach and prolonged heat. The dye is stable, but there is no reason to test it. Ultrasonic cleaners are usually fine on solid, unfractured stones — we would still rather you didn't.