Those Fabulous Feldspars
Moonstones and rainbows, dark blue, turquoise, yellow and white! Feldspars are among the most common minerals on Earth - and yet exhibit fascinating textures and colors.
One simple, chemical diagram explains the three chemical end-members - and all our feldspars can be mapped onto that diagram. Add some Iron (Fe), Copper (CU) or cool the feldspars slowly in a deep magma chamber, and we get all sorts of wonderful results.