Van Cleef & Arpels Vintage Alhambra Onyx Pendant Necklace 18K Yellow Gold

If you only own one piece from the house, it's usually this one. A four-leaf clover on a fine chain, a design from 1968 that hasn't needed changing. The pendant is fixed to the chain at two points, so it hangs flat and stays facing forward. It doesn't spin or slide around to the clasp.

Onyx gives it an edge the lighter stones don't have. It's polished flat and truly black, and the gold beads around it look brighter for the contrast. It goes with everything, which sounds like a cliché until you've worn it with a white shirt, a black sweater and a dress in the same week.

The chain has a second ring so you can wear it at two lengths, higher on the neck or a little lower. Lobster clasp, with the maker's tag beside it.