A colorful scapolite grain is enclosed in a single, multiply twinned crystal of microcline, a variety of feldspar. Periodic offsets in the regular atomic structure of crystals produces twinning, which may develop during crystal growth or result from later deformation. Twinning takes many different forms in minerals; the tartan plaid pattern you see here is a characteristic feature of microcline that helps to distinguish it from other feldspars.

Crossed polarizers