
65Blasting and Earth Movement
metamorphic rock is the foliated structure that refers to the nearly parallel arrangement of
platy or needlelike minerals. Some of the typical metamorphic minerals found in foliated
rocks are chlorite, sericite, talc, hornblende, and biotite. Depending upon the grain size
of the crystals, the structure may be described as gneissic (coarse), schistose (medium), or
slaty (microscopic).
A large group of metamorphic rocks, most of which are derived from sediments,
possesses a massive rather than a foliated structure. ese may be distinguished from the
parent sediment by their greater density, hardness, and crystal