Semi-precious stone with a distinctive intense ultramarine blue colour, with minute pyrite crystals, sometimes gold in colour, creating a beautiful golden shimmer. It was used by Renaissance and Mannerist craftsmen for flasks (e.g. a flask with a handle in the form of harpies and fittings of gold and enamel, late 16th century; Florence, Pitti) and vases, and as a component in pietra dura inlay.