Nonfoliated refers to a type of metamorphic rock that does not exhibit any layering or banding. Unlike foliated rocks, which have a distinct alignment of minerals due to high pressure and temperature during metamorphism, nonfoliated rocks are characterized by a more uniform texture and the absence of any planar features.
Common examples of nonfoliated metamorphic rocks include marble and quartzite. Marble is formed from the metamorphism of limestone and consists primarily of calcite or dolomite, while quartzite forms from the metamorphism of quartz sandstone and is composed mainly of quartz grains. The formation of nonfoliated rocks occurs under conditions where pressure is applied equally in all directions, or the heat is the dominant factor, allowing the minerals to grow and interlock without any directional arrangement.