How do I care for antique onyx jewellery?

Onyx is a relatively soft stone compared to diamond or sapphire, rating around six to seven on the Mohs scale. Clean pieces gently with a soft damp cloth rather than harsh chemical dips or ultrasonic cleaners. Store items individually in lined boxes to prevent harder gemstones from scratching the polished black surface. Avoid wearing them during manual tasks to protect the delicate metal settings.

How do I date a piece of onyx jewellery?

Dating relies upon a combination of metal hallmarks, gemstone cuts, and overall design style. Victorian pieces often use heavy yellow gold and closed-back settings, while Art Deco items favour platinum, white gold, and geometric layouts. Maker marks and registration numbers stamped on the shank or clasp provide precise chronological clues. Comparing the construction methods against known historical periods confirms the era of manufacture.

Is black onyx always natural?

Much of the historical black chalcedony used in jewellery underwent treatment to enhance its uniform colour. This historical practice involved soaking grey chalcedony in sugar solutions and acid. Natural black stones exist, but treated varieties have been common since antiquity due to the stone's porous nature. Both historical treated stones and natural specimens hold equal place in antique collections.

Can I resize an antique onyx ring?

Resizing depends entirely on the construction of the shoulders and whether the onyx forms a continuous structural band. Plain signet rings and simple gold shanks usually allow straightforward adjustment by a skilled jeweller. Complex Art Deco mounts with channel-set stones risk fracture or distortion if heated near the gems. Consult a specialist familiar with antique settings before attempting any alterations.