In doubly-refractive stones, lthe light entering the stone is split into two light rays, and the rays travel in different paths. These stones have more than one refractive index . Calcite, peridot , zircon , tourmaline , and titanite are doubly-refractive stone. This type of stone makes a nice pendant . A ductile substance is easily pulled or stretched into a thin wire.
Gold is the most ductile metal.
Du Jay items are hard to find. Dumortierite quartz is a massive variety of opaque quartz that is intergrown with dumortierite crystals.