Limestone is formed partly by chemical processes and partly biological process. Most limestone is composed of skeletal fragments of marine organisms such as coral. Pure limestone is white or almost white, but because of impurities, such as clay, sand, organic remains, iron oxide and other materials, many limestones exhibit different colors, especially on weathered surfaces. Acids have a corrosive effect on limestone or marble buildings or sculptures.
It is well established that either wet or dry deposition of sulfur dioxide significantly increases the rate of corrosion on limestone, sandstone and marble. Limestone deposits lead to narrowing of the inside diameter of water pipes, and in extreme cases may cause complete blockage. Limestone deposits have been found in larger boilers that can measure up to several centimeters thick.
They can cause serious technical problems for heating and water supply systems. The buildup of limestone deposits inside heating systems and hot water reservoirs leads to the reduction of heat exchanged between the heating water or industrial water and the heat source. Corrosion and limestone deposits in plumbing systems lead to broken pipes, blockages and eventual flooding.
Increased energy and water consumption as well as all other related costs are results of diminished performance of heating installations. It is sawn or sheared into floor tiles, window sills, wall panels, stair treads, and other shapes, mainly for interior use. High-quality material can sometimes accept a polish. The material can be recognized by its low hardness 3 on the Mohs scale , banded appearance, and porous texture. Tufa is a porous rock that forms from the precipitation of calcium carbonate, often at a hot spring or along the shoreline of an alkaline lake where waters are saturated with calcium carbonate.
Tufa is a porous limestone produced by precipitation of calcium carbonate from the waters of a hot spring or other body of surface water that has the ability to precipitate volumes of calcium carbonate.
The pore space in tufa often results when plant material is trapped in precipitating calcium carbonate. One of the most famous locations where tufa is actively forming is at Mono Lake, Yosemite National Park.
The most spectacular tufa features at the lake are known as "tufa towers". They form by the interaction of freshwater springs and alkaline lake water. In spite of its gnarly appearance as a rock, tufa actually has numerous architectural uses. When found in thick accumulations, tufa can be mined and sawn into blocks and sheets just like any other dimension stone. It produces a stone with a very rugged appearance.
Crushed Limestone: The Unsung Mineral Hero: Crushed stone is often looked upon as one of the lowliest of commodities; however, it is used for such a wide variety of purposes in so many industries that it should be elevated to a position of distinction.
It is the geologic commodity upon which almost everything is built. The Wordle word cloud above shows just a few of its many diverse uses. Limestone is a rock with a diversity of uses. It could be the one rock that is used in more ways than any other. Most limestone is made into crushed stone that is used in road base, railroad ballast, foundation stone, drainfields, concrete aggregate, and other construction uses. It is fired in a kiln with crushed shale to make cement.
Some varieties of limestone perform well in these uses because they are strong, dense rocks with few pore spaces. These properties enable them to stand up well to abrasion and freeze-thaw.
Although limestone does not perform as well in these uses as some of the harder silicate rocks, it is much easier to mine and does not exert the same level of wear on mining equipment, crushers, screens, and the beds of the vehicles that transport it. In many parts of the world, the harder silicate rocks are too far from construction sites to be used economically.
A Gem of Crinoidal Limestone: This cabochon was cut from a piece of fossiliferous limestone that is rich in crinoid debris. Crinoids are organisms that have the morphology of stemmed plants but are actually animals. Rarely, crinoidal and other types of limestone have the ability to accept a bright polish and have interesting colors and patterns. These specimens can be made into unusual and beautiful organic gems. This cabochon is about 39 millimeters square and was cut from material found in China.
The Loyalhanna is a Late Mississippian calcareous sandstone to arenaceous limestone, composed of siliceous sand grains embedded in and bound by a matrix of calcium carbonate. In outcrop, the Loyalhanna is cross-bedded with features that have caused geologists to argue if it is of marine bar or eolian dune origin. As a construction material, the Loyalhanna is valued as an anti-skid aggregate crushed stone.
When it is used to make concrete paving, sand grains in aggregate particles exposed on a wet pavement surface provide traction for tires, giving the pavement an anti-skid quality. Limestone has many other uses. Powdered limestone is used as a filler in paper, paint, rubber, and plastics.
Crushed limestone is used as a filter stone in on-site sewage disposal systems. Powdered limestone is also used as a sorbent a substance that absorbs pollutants at many coal-burning facilities. Limestone is not found everywhere. It only occurs in areas underlain by sedimentary rocks. When limestone is needed in other areas, buyers sometimes pay five times the mine-site cost of the stone in delivery charges so that limestone can be used in their project or process.
The best way to learn about rocks is to have specimens available for testing and examination. Article by: Hobart M. Limestone Stalactite A water drop clings to a stalactite. If it evaporates instead of falling, any dissolved calcium carbonate will add to the stalactite. National Park Service photo. Style: MLA.
English Language Learners Definition of limestone. Kids Definition of limestone. Get Word of the Day daily email! Test Your Vocabulary. Test your visual vocabulary with our question challenge! Love words? Need even more definitions? Although it occurs in many different forms, its origins can be traced back to either chemical or biochemical processes that occurred in the geological past, often tens to hundreds of millions of years ago.
Many different types of marine organisms have developed the ability to precipitate calcium carbonate from seawater to serve as a protective shell or exoskeleton.
For example, scallops have a two-piece outer shell that can be opened to allow the scallop to feed and closed to give protection, whereas bryozoans produce an outer casing within which they can live. When these organisms die, their shells accumulate on the seafloor. The soft parts decay, leaving only the hard shells exoskeletons or tests , which typically become broken down by current action and biological predators.
Over long periods of time, the loose skeletal sediments are transformed into bioclastic limestone by the addition of a chemically precipitated carbonate cement between the shell fragments.
In the warm low-latitude waters of the tropics, these are called tropical bioclastic limestones, while in the cooler waters, at mid to high latitudes, they are known as temperate bioclastic limestones. In the case of large congregations of tropical marine organisms, like reef-building corals, the normally very large structure remains intact as it is transformed into tropical limestone reef rock.
Converting accumulated cool-water shell sediments into rock consists of several steps.
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