Building stone is any kind of stone that is used to construct building or retaining walls. Building stones are categorized as sandstones, limestones, fieldstones, granites and river rock. Most full-thickness building stones for masonry walls are 4″ – 6″ thick although this varies from stone to stone.
Sand was generated in enormous quantities worldwide as erosion ground down many generations of mountain ranges. Because of the great variety of environments in which they were created, sandstones are available in a wide range of colors, shapes, and textures.
Limestones, and a modified form called dolomite, were deposited in reefs, lagoons, and as fine-grained calcium carbonate sediment (chalk) on the ocean floor. Most limestones are light-colored (light gray, buff, tan) with textures that range from very dense and fine grained to coarse-textured and fossil rich.
Fieldstones can consist of any type of rock. They are collected from at or near the surface and are usually weathered and sometimes covered with lichens.
Granite, gneiss (pronounced “nice”), and quartzite are crystalline igneous and metamorphic rocks. Although they vary greatly in appearance, they are generally the hardest and most durable of masonry stones.
River rock is cobble-to-boulder-size stone that has been rounded by transport in a river or stream. The best river rock has some flat surfaces and angles so that it stacks well, minimizing joint widths and forming good corners.