DIRK WIERSMA / SCIENCE PHOTO LIBRARY DIRK WIERSMA / SCIENCE PHOTO LIBRARY
Gneiss boulders in a river. Gneiss is formed from other types of rock that are subjected to intense heat or pressure (metamorphism). These extreme forces, typically found in the roots of mountains, obliterate the rock's original structure and cause minerals to recrystallize in bands. In gneiss, the bands are coarse-grained and consist of three minerals: mica (dark bands) alternating with a mixture of quartz and feldspar (light bands). Photographed in the Maggia Valley, Ponte Brolla, Switzerland.
Model release not required. Property release not required.