Limestone: An Overview
Limestone is one of the most popular dimension stones used in residential and commercial applications. Limestone is a sedimentary rock composed primarily of calconite and aragonite minerals and crystallized calcium carbonate. Many limestone formations contain skeletal fragments of marine organisms such as coral.
The Formation of Limestone:
The majority of limestone formations are created from skeletal fragments of marine organisms. Composing approximately ten percent of the total volume of sedimentary rocks, limestone is formed by mineral deposits at the earth¹s surface and within large bodies of water. Mineral and organic particles settle and accumulate as a result of weather conditions and erosion. After the particles have settled, they are transported by the mass movement of water, wind and ice to the location of the primary rock formation.
Limestone contains varying amounts of clay, silt, sand and organic material transported by rivers and streams. Various amounts of silicon dioxide, also known as silica, create the hardness and texture found in limestone. Silica is often found in the form of chalcedony and jasper, which are recognized as semi-precious gemstones. The color variations found in limestone are due to the trace elements and impurities present in the rock formations, such as sand, silt, clay, iron oxide and organic remains. Limestone is commonly formed in clear, shallow marine waters, but may also be formed by the saturation of calcium carbonate from lakes or ocean waters.
Limestone contains approximately 50 percent calcium carbonate, in addition to small particles of quartz, feldspar, clay minerals, fossilized marine organisms and sand. Limestone can have crystalline, granular or fragmented surfaces, depending on the geographic location and method of the rock formation. Calcite, quartz or dolomite crystals line small crevices in limestone rock. In wet conditions, calcite forms a mineral coating that naturally cements the rock particles and grains together, filing fractures and increasing the density and strength of the rock.
There are several varieties of limestone, all of which can be sanded and polished to create a desired surface.
Chalk limestone is formed from shell remains of microscopic marine organisms. It is a soft stone with a fine texture, usually white or light gray in color.
Coquina limestone is formed on beaches and is composed of broken or fragmented shell debris. The natural surface texture is rough and porous.
Fossiliferous limestone contains an accumulation of large fossils shells and skeletal remains of the organisms that originally formed the limestone.
Lithographic limestone, a dense rock with fine and uniform grains is formed in shallow beds that separate easily to form a smooth, even surface.
Oolitic limestone is primarily composed of small calcium carbonate spheres, creating a concentric surface.
Travertine is formed by evaporation, usually in caves or adjacent to waterfalls or natural springs.
Tufa limestone is created in calcium-rich waters near natural hot springs or lake shores. This type of limestone is characterized by a porous and uneven surface.
Residential and Commercial Uses of Limestone:
As a versatile and diverse natural stone, limestone is widely used in residential and commercial applications. Limestone is available in a variety of finishes including honed, polished, tumbled and satin. Honed and satin finishes are popular for residential uses as flooring in low-traffic areas, wall coverings, wainscoting, door panels and fireplace surrounds. Polished finishes are popular for use as kitchen countertops, backsplashes, bathroom walls and accent tiles surrounding natural stone or hardwood floors. Limestone is available in various textures and colors including light shades of blue, green, gold and ivory.
The heat and moisture-resistant qualities of limestone make the stone ideal for outdoor uses including hot tub or swimming pool coping, deck or patio railings, stair risers and window trim. Limestone can be used in landscaping projects, including garden paving stones and retaining walls.
As limestone can withstand extreme weather conditions, it is commonly used as facings on large commercial buildings including high-rise office towers, apartment complexes, condominium developments and memorials. Crushed limestone, which is moisture and heat resistant, is popular for use as a coating for asphalt roofing shingles and as a top coat for industrial built-up roofs.