Classic Amethyst and Citrine Specimen

A classic Chihuahua state of Mexico crystal specimen. Probably mined in the early 1990s. Amethyst and Citrine are only delineated by their color. They are both silica dioxide crystals. The only difference is that Amethyst is purple and Citrine is yellow. Both gain their color from iron inclusions in the crystal structure. When they are both on the same specimen it usually comes from differing oxidation levels of the iron in the individual crystals!