February's traditional birthstone, pretty purple amethyst is the most valuable gemstone in the quartz group. Amethyst is also special because its crystal structure differs from the other crystal quartzes, even though it has the same hardness, moderate refraction, and weight. Amethyst's stratified construction creates varying color intensity and explains why there are only a select few large gem amethysts with evenly dispersed rich color, even with its abundance around the world. Whether in faceted stones, crystal specimens, polished pebbles, or beads, amethyst has enjoyed popularity in nearly every culture throughout its ancient history.