Pressure shadow
A pressure shadow is a term used in metamorphic geology to describe a microstructure in deformed rocks that occurs adjacent to a relatively large, undeformed particle, such as a porphyroclast. Pressure shadows often appear in thin sections as pairs of roughly triangular regions that are elongated parallel to the foliation around a clast of a different mineral. Pressure shadows that contain fibrous mineral textures are also termed pressure fringes or strain fringes.