To cheer up a rainy day, one of the local antique dealers at the fleamarket was doing a £2 sale, an entire stall full of things that looked like evidence from detective stories; unusual brooches, broken ornaments, odd piles of buttons, fragments of filigree and paste. I picked this out for my stepfather, an archeologist who's fond of roughish celtic jewellry. As I bought it, the stallholder tapped the bead. "Possibly haematite," she said, "it's cool to the touch." Cool. And shiny!