A beach composed chiefly of surface pebbles is generally termed a shingle beach. This type of beach has armoring characteristics with respect to wave erosion, as well as ecological niches that provide habitat for animals and plants. Pebbles come in various colors and textures, and can have streaks of quartz and unique colored sedimentary rock. Pebbles are mostly smooth but, reliant on how frequently they come in contact with the sea, they can have marks of contact with other rocks or other pebbles. Pebbles left above the high water mark may have growths of creatures such as lichen on them, signifying the lack of contact with seawater.