Storage
Where and how a piece is kept between wears. More damage happens in the box than on the body.
Pearls need a breathable cloth pouch, stored flat and separately, with a little ambient humidity. Sealed plastic dries them out.
Silver wants the opposite: an airtight bag with an anti-tarnish strip, away from air and sulphur.
Everything should be stored so pieces do not touch. Diamond scratches sapphire, sapphire scratches pearl, and every metal scratches nacre.
When you are buying
The pouch a piece arrives in is not packaging, it is the correct storage. Keep it, and store strands flat rather than hanging so the thread does not stretch.
Pearl Care
Pearls are soft and porous. They need to go on last, come off first, and be stored apart from everything else.
Tarnish
The dark film that forms on silver as it reacts with sulphur in the air. Surface only, and it polishes off.
Restringing
Replacing the thread a strand is built on. Routine maintenance, not repair, and overdue on most pearl necklaces.
Yellowing
The gradual browning of old pearls as the protein binding the nacre oxidises. Usually irreversible.
Onyx
A black chalcedony, usually dyed to an even colour. Common as a contrast bead beside white pearls.