Moissanite

Moissanite is lab-grown silicon carbide, and it behaves like a gemstone rather than a stand-in: 9.25 on the Mohs scale, second only to diamond, with a higher refractive index than diamond and roughly twice the dispersion, which is why it throws more colour.

The category currently holds 367 pieces: 109 rings, 94 pairs of earrings, 68 pendants, 14 necklaces, 7 bracelets and 75 loose stones, from $1.9 for a single loose stone up to $1,418 for a 10ct ring in 18K gold. 292 of the finished pieces are set in metal, split between 18K gold and gold-plated S925 sterling silver; the other 75 are unset stones for jewellers and setters.

At 9.25 it will scratch almost everything else in a jewellery box, including other moissanite, so store it in its own pouch. Warm water, mild soap and a soft brush are enough to bring the fire back.