C A T O C T I N   M E T A B A S A L T

Columnar jointing in metabasalt of the ~570 Ma Catoctin Formation exposed along the Skyline Drive, Shenandoah National Park, northern Virginia Blue Ridge province

Photomicrograph of Catoctin metabasalt (greenstone) from the Blue Ridge province. Plagioclase (p) phenocrysts in a fine-grained matrix (m) of chlorite, epidote, and magnetite. Field of View 5 mm x 33 mm, plane polarized light.