Chemistry in Pictures: Chatoyancy

The color of a mineral is about more than just its chemical composition. For some rocks, the precise arrangement of crystal phases can result in physical color and other optical effects. This sample of labradorite, a calcium-enriched type of feldspar, is a prime example of chatoyancy, the phenomenon of physical color changing on the basis of the viewing angle. The rock was collected in Labrador, Canada, in 1955 and is now on display with other geological wonders at the Gallery of Mineralogy and Geology in Paris.

Credit: Craig Bettenhausen/C&EN