Fluorite “Ice Cubes”, Galena & Quartz
Fluorite
– CaF2
Fluorite
Talc (1)Diamond (10)
Softer than glass. A steel knife scratches it.
Did you know?
Fluorite gave fluorescence its name. In 1852 the physicist George Stokes, studying the mineral's glow under invisible light, coined the word for the whole phenomenon after the stone itself.
Galena was the heart of the first crystal radios. Acting as a natural semiconductor, it let a fine wire called the cat's whisker pull voices from the air with no battery at all.
Pressing a quartz crystal makes it give off a precise electric beat, which is why it keeps time in nearly every watch and once tuned the radios of World War II, when good crystals were a strategic resource.
