Tourmaline: one mineral group, an enormous range of colors

Tourmaline is famous for its color range, a single crystal can even show two or three distinct colors along its length, watermelon tourmaline (pink center, green outer layer) being the most well known example of this zoning. Hardness runs about 7 to 7.5. A genuinely useful identifying property is pleochroism, tourmaline often appears a different shade of color depending on the angle you view it from, which can be checked by rotating a transparent piece under a light source. Tourmaline typically forms in pegmatites, the same coarse grained granite environment that produces large beryl and quartz crystals, which is why the three are often found together in the same deposits.