Written for the April 2015 WCGMC newsletter
Since the days of the Roman Empire, purple has been the color of royalty. As a combination of red and blue, purple is not a spectral color and therefore lacks a defining spectral wavelength. However, that has not prevented people from claiming purple to be their absolutely favorite color. Women build their wardrobes around their purple dresses, folks paint their bedrooms purple, gardeners plan their seasonal blooms from tulips to irises to petunias, and yes mineral collectors must have plenty of purple in their displays. Fortunately they have some wonderfully gorgeous minerals from which to choose.
March 13th was Purple Mineral Night for the Wayne County Club. Members brought in their purple minerals and we all drooled over them. Naturally there was lots of amethyst in attendance. Simple clear quartz (SiO2) is colored to various shades of purple when small amounts (< 20 ppm) of iron (Fe) replace Si when the quartz is naturally exposed to ionizing irradiation. The smaller iron atom leads to lattice distortions that effect light passage imparting the color variation. With a hardness of 7, amethyst makes a wonderful gemstone as well as a colorful mineral specimen.