Did you know?
Sphalerite is named from the Greek for treacherous, because it fooled old miners hunting for lead. Gem-clear pieces hide a second surprise: they scatter light into rainbow fire more than three times stronger than a diamond.
Look through a clear rhomb of Iceland spar calcite and the world doubles, split into twin images by the crystal's double refraction. Some researchers think Norse sailors used this very effect to find the sun through cloud, the so-called sunstone, though the idea remains a debated hypothesis.
