These ones don't spin
The necklace and the ring both rotate — that's the point of them. These don't, and they were never meant to. An earring you have to reach up and fiddle with is an earring you eventually take off. These are the piece that stays put while the others do the work.
Why studs rather than drops
A drop earring catches on scarves, on hair, on the strap of a bag. A flat stud doesn't, which is why this is the shape people actually keep wearing rather than saving for occasions. It also means they can be slept in, which matters more than most jewellery admits.
The stone
Opal shifts colour depending on the light it's in — warm and milky indoors, blue-white in daylight. The halo of small stones around it is there to catch that movement and make it visible from a distance.
Looking after them
Gold-plated copper, so keep them dry and put them on after perfume and hairspray rather than before. Treated that way the plating lasts far longer.