chromite banding cumulate dunite

A beautiful banded talus boulder with a 4-lb sledgehammer for scale exhibits rhythmic bands of chromite crystals in dunite. The banding is attributed to differential gravitative settling of both the black chromite and light-colored olivine crystals during crystallization within an ultramafic magma chamber. These bands were originally horizontal.
Twin Sisters Mountain, Whatcom County, Washington, USA
Photographed in 2014