Greys and violets

These are the pieces that change on you. Grey when you put them on indoors, properly violet by the time you are standing outside, and back again when the afternoon goes flat. Nothing is happening to the stone — it is translucent, so the colour you see depends on what is behind it and how much light is getting through.

They tend to be the heavy ones. A dense stone hangs low and moves slowly, and a pendant that moves slowly makes you carry yourself differently from the way a light chain does. People buy these for winter, and for weeks that need something serious hanging off them.

This is also the family where naming the stone would be easiest to get wrong. Several quite different materials go smoky grey at the top and deep violet at the bottom, and from a photograph they are indistinguishable. So the listing describes the colour, the translucency and the weight, and stops there.