Did you know?
Barite feels surprisingly heavy for a pale crystal, the weight of its barium. Around 1603 a Bologna shoemaker roasted some and found it glowed in the dark, the Bologna stone, the first artificial phosphor ever made.
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.
