What Chemical Elements Are Found in Limestone?
- Calcium The first element found in limestone is calcium; the symbol for calcium is Ca. ...
- Carbonate Ion The carbonate ion, CO3 -2, consists of a central carbon atom surrounded by three oxygen atoms in a triangular formation. ...
- Chemical Reactions The carbonate ion can accept a hydrogen ion to become bicarbonate, HCO3 with a -1 charge. ...
- Origins and Fate ...
How is limestone formed?
Limestone is any rock that is made mostly from calcium carbonate, but there are several types. It forms with carbonate rocks were deposited in seawater and continue to form as coral reefs in shallow seas.
Is limestone a type of carbonate?
"Limestone" means any rock formed mostly of calcium carbonate (CaCO 3), but to geologists, limestone is only one of several types of "carbonate rocks." These rocks are composed of more than 50% carbonate minerals, generally the minerals calcite (pure CaCO 3 ) or dolomite (calcium-magnesium carbonate, CaMg[CO 3 ] 2 ) or both.
What happens when you add an acid to limestone?
But if you add an acid, you add hydrogen ions (H+), which will react with the carbonate to form hydrogen carbonate HCO3- ions, which are very soluble in water, and the limestone will dissolve. Or, if there is more acid, two hydrogen ions will react with a carbonate to form carbonic acid - H2CO3 - which will decompose to form carbon dioxide -...
What is the source of calcium in limestone?
Other limestones are primarily composed of recrystalised lime mud, and are referred to as micrite . The primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, building upon past generations.
How limestone is formed?
Limestone is formed almost exclusively by organisms in seawater (although there are some freshwater limestones too), either, by direct crystallization of dissolved calcium and carbonate to form shells, or as a by-product of the presence of organisms in seawater (which can alter the overall geochemical setting).
What element forms limestone?
Limestone is a sedimentary rock composed principally of calcium carbonate (calcite) or the double carbonate of calcium and magnesium (dolomite). It is commonly composed of tiny fossils, shell fragments and other fossilized debris.
Is limestone formed chemically?
Chemical limestones Some limestones are formed by direct chemical precipitation from marine and other waters saturated with calcium carbonate. If carbon dioxide is removed from this water by warming, agitation or photosynthesis, there is a tendency for calcium carbonate to be precipitated.
What does limestone need to form?
Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. The solubility of calcium carbonate ( CaCO 3) is controlled largely by the amount of dissolved carbon dioxide ( CO 2) in the water.
Where is limestone formed?
Most limestone layers formed from marine sediment deposited on sea floors, although some formed in freshwater lakes and rivers and even on dry land.
How limestone is formed simple?
Limestone is a type of rock that is made up of bits of animal shells. Over millions of years these shells collected on the ocean floor. As layers of shells and mud built up, the lower layers slowly hardened into limestone. Limestone is found all over the world.
How is limestone made and what is it made from?
Limestone is usually a biological sedimentary rock, forming from the accumulation of shell, coral, algal, fecal, and other organic debris. It can also form by chemical sedimentary processes, such as the precipitation of calcium carbonate from lake or ocean water.
Is limestone a chemical or chemical reaction?
The heating of limestone is a chemical change; the limestone decomposes into two other substances, lime and carbon dioxide. The symbols after each formula show the physical state of that substance.
Is limestone formed by chemical weathering?
Limestone is chemically weathered by a process of carbonation. As rainwater absorbs carbon dioxide as it passes through the atmosphere it becomes a weak carbonic acid. The water and carbon dioxide combine to form a weak carbonic acid. This weak carbonic acid acts on the fissures in the limestone.
Is limestone chemical or biological?
Limestone. Limestone is comprised of calcite and aragonite. It can occur as a chemical sedimentary rock, forming inorganically due to precipitation, but most limestone is biochemical in origin.
Is limestone a physical or chemical property?
Physically, Limestone are Quite impervious, Hard, Compact, fine to very fine grained calcareous rocks of sedimentary nature. Chemically, both limestone and marbles are siliceous calcium carbonate rocks. Limestone, like marble and other calcareous stones, are referred to as acid sensitive.
What is Limestone?
" Limestone " means any rock formed mostly of calcium carbonate (CaCO 3 ), but to geologists, limestone is only one of several types of "carbonate rocks." These rocks are composed of more than 50% carbonate minerals, generally the minerals calcite (pure CaCO 3) or dolomite (calcium-magnesium carbonate, CaMg [CO 3] 2) or both.
What are the different types of limestone?
Limestone comes in many different varieties. Chalk is a very fine-grained, porous marine limestone composed almost entirely of microscopic fossils. Travertine is a freshwater sedimentary limestone that has very thin, crenulated layers and is commonly formed at springs. Marble is a carbonate rock, usually a marine limestone, that has been squeezed and deformed like plastic by great heat and pressure deep beneath the Earth's surface. This process is called "metamorphism." There are also rare "igneous" carbonate rocks that have crystallized from molten magma in the same way that lavas or granites have. These are called "carbonatites," and this rock type is mined at a few places in the world as industrial limestone.
How much limestone was imported in 2007?
In 2007, domestic production of industrial limestone was about 1.3 billion metric tons, valued at more than $25 billion. In the same year, the Nation imported about 430,000 metric tons of industrial limestone and limestone products, valued at about $2.2 billion. Most of these imports were Portland cement.
What are the two chemicals that make up the shells of the ocean?
In the near-surface layer of most oceans, corals, clams, and other sea-dwelling creatures use these two chemicals to make protective shells by combining them to form calcite or "aragonite, " which is the same chemical composition as calcite but has a different crystal form.
How thick is limestone?
Therefore, limestone quarries can be large and long lived, mining limestone layers that can be hundreds of feet thick over areas of several square miles.
How has limestone changed?
Some limestones have been changed by the introduction of magnesium in groundwater. Magnesium in groundwater may convert some or all of the calcite in the limestone to dolomite. Also, some rocks formed near the shores of ancient seas in arid climates were mostly dolomite at the time they were deposited.
What are some products made of limestone?
Some of the many products made using limestone are shown in this photograph: breakfast cereal, paint, calcium supplement pills, a marble tabletop, antacid tablets, high-quality paper, white roofing granules, and portland cement.
What is the chemical formula for limestone?
Limestone is a sedimentary rock composed of a mineral called calcite, which has the chemical formula CaCO3. Together with the dolomites, a related class of sedimentary rocks, limestone makes up some 10 to 15 percent of all sedimentary rock on our planet. Some limestone is a product of material made by living organisms;
How many protons does calcium have?
Calcium has atomic number 20, meaning it has 20 protons in its nucleus. The pure element has 20 electrons. Like other metals in the same group, the alkaline earth metals, calcium is easily ionized, so in nature it's found as part of other compounds (like calcium carbonate). Calcium carbonate is an ionic compound, ...
What is the reaction of carbonate and hydrogen?
Chemical Reactions. The carbonate ion can accept a hydrogen ion to become bicarbonate, HCO3 with a -1 charge. The bicarbonate ion can in turn accept another hydrogen ion to become carbonic acid, H2CO3. When in water, the carbonic acid is in equilibrium with carbon dioxide in the air, so if excess carbonic acid is present, ...
What is the name of the rock that is formed by a rock that is buried deep in the ocean?
Limestone may also develop from dripping water in caves; the water carries dissolved calcium carbonate, which precipitates to form a kind of limestone called travertine. If buried deep and subjected to high heat and pressure, limestone can become a kind of metamorphic rock called marble.
Does calcium carbonate dissolve in acidic solutions?
In limestone, however, the attraction between the calcium and carbonate ions is strong enough that calcium carbonate does not dissolve in neutral solutions. It only dissolves readily in acidic solutions. Adding hydrochloric acid to limestone, for example, will rapidly cause it to fizz. Advertisement.
Is calcium carbonate ionic or nonionic?
Calcium carbonate is an ionic compound, meaning that calcium has lost two electrons to become a positively charged ion, while the carbonate group has gained two electrons to become a negatively charged ion. The attraction between positive and negative charges holds the two ions together to form the crystal structure. Advertisement.
What color is limestone?
Limestone that is unusually rich in organic matter can be almost black in color, while traces of iron or manganese can give limestone an off-white to yellow to red color. The density of limestone depends on its porosity, which varies from 0.1% for the densest limestone to 40% for chalk.
Why is limestone important?
Limestone is a huge industrial material that is in constant demand. This raw material was and has been essential in the iron and steel industry since the nineteenth century. Companies never had a shortage of limestone, however it was a concern as the demand continued to increase and in fact is still in high demand today. The major potential threats back in the nineteenth century were regional availability and accessibility. The two main accessibility issues were transportation and property rights. Other problems were high capital costs on plants and facilities due to environmental regulations and the requirement of zoning and mining permits. These two dominant factors lead to the adaptation and selection of other materials that were created and formed to design alternatives for limestone that suited economic demands.
What classification scheme is used to identify carbonate rocks?
Two major classification schemes, the Folk and Dunham, are used for identifying the types of carbonate rocks collectively known as limestone.
What is the hardness of limestone?
Limestone outcrops are recognized in the field by their softness (calcite and aragonite both have a Mohs hardness of less than 4, well below common silicate minerals) and because limestone bubbles vigorously when a drop of dilute hydrochloric acid is dropped on it.
How much crushing strength does limestone have?
Although relatively soft, with a Mohs hardness of 2 to 4, dense limestone can have a crushing strength of up to 180 MPa. For comparison, concrete typically has a crushing strength of about 40 MPa.
Why is it so hard to remove graffiti from limestone?
Removing graffiti from weathered limestone is difficult because it is a porous and permeable material. The surface is fragile so usual abrasion methods run the risk of severe surface loss. Because it is an acid-sensitive stone some cleaning agents cannot be used due to adverse effects.
How is dolomite formed?
Much dolomite is secondary dolomite, formed by chemical alteration of limestone. Limestone is exposed over large regions of the Earth's surface, and because limestone is slightly soluble in rainwater, these exposures often are eroded to become karst landscapes. Most cave systems are found in limestone bedrock.
What is Limestone?
Limestone is a sedimentary rock composed primarily of calcite, a calcium carbonate mineral with a chemical composition of CaCO 3. It usually forms in clear, calm, warm, shallow marine waters.
How does limestone form?
Limestone is usually a biological sedimentary rock, forming from the accumulation of shell, coral, algal, fecal, and other organic debris. It can also form by chemical sedimentary processes, such as the precipitation of calcium carbonate from lake or ocean water.
What is a fossilized limestone?
Fossiliferous limestone is a limestone that contains obvious and abundant fossils. They are usually marine invertebrates such as brachiopods, crinoids, mollusks, gastropods, and coral. These are the normal shell and skeletal fossils found in many types of limestone.
What is the name of the metamorphic rock that forms when limestone is subjected to the heat and pressure of?
Marble is the name of the metamorphic rock that forms when limestone is subjected to the heat and pressure of metamorphism. It is composed of calcium carbonate (CaCO 3) and usually contains other minerals that might include clay minerals, micas, quartz, pyrite, iron oxide, and graphite.
What happens when limestone is subjected to heat, pressure, and chemical activity?
When limestone is subjected to heat, pressure, and chemical activity, the calcite in the rock begins to transform. This is the beginning of the process known as metamorphism. Starting at a microscopic scale, the calcium carbonate in the rock begins to crystallize or recrystallize into fine-grained calcite crystals.
What is Coquina limestone made of?
Coquina is the name of a poorly cemented limestone composed almost exclusively of sand-size fragments of calcareous shell and/or coral debris. A small amount of calcareous cement usually binds the grains together.
What is the name of the limestone that forms from an accumulation of calcareous shell remains of microscopic marine?
Chalk is the name of a limestone that forms from an accumulation of calcareous shell remains of microscopic marine organisms such as foraminifera. It can also form from the calcareous remains of some marine algae.
What are the analogues of carbonate deposits?
In addition to the ancient analogues of the modern carbonate deposits described above are freshwater limestones ( marls) and limestone muds (or calcilutites) of deep-water abyssal plains. Freshwater limestones of limited extent represent a spectrum of small-scale settings developed within and along the margins of lacustrine basins. Deep-water abyssal plain limestones are quite restricted in volume and age in the geologic record for a number of reasons. First of all, abyssal plain sequences are less likely to be incorporated into the orogenic belts that develop as continental margins are compressed during ocean basin closure. Second, pelagic calcareous oozes are the obvious modern analogues of ancient abyssal plain calcilutites. These oozes are produced by aragonite-secreting plankton that float near the surface (such as foraminiferans and coccoliths), which upon their death leave their shells, or tests, to settle slowly to the ocean bottom and accumulate. The development of such deep-sea deposits is therefore obviously dependent on the existence of calcium-secreting planktonic organisms, and these did not evolve until Mesozoic time. Finally, calcareous ooze accumulation is severely restricted both by latitude (being largely confined to a band extending 30° to 40° north and south of the Equator) and abyssal plain depth (approximately 2,000 metres). Below a depth of about 4,500 metres, which is the carbonate compensation depth (CCD), the pressure and temperature of seawater produces a rate of dissolution in excess of the rate of pelagic test accumulation.
How is dolomite formed?
Dolomite is produced by dolomitization, a diagenetic process in which the calcium carbonate minerals aragonite and calcite are recrystallized and converted into the mineral dolomite. Dolomitization can obscure or even obliterate all or part of the original limestone textures and structures; in the case where such original features survive, carbonate nomenclature and interpretation can still be applied to the rock with emphasis on the effects of alteration.
What is the best known carbonate setting?
Modern carbonate sediments are generated in a variety of environments: continental, marine, and transitional, but most are marine. The present-day Bahama banks is the best known modern carbonate setting. It is a broad submarine shelf covered by shallow, warm seawater. The Bahama shelf, or carbonate platform, mimics the setting ...
Do limestones dolomite?
The exact processes by which limestones are dolomitized are not thoroughly understood , but dolomites occur widely in the geologic record. The relative proportion of dolomite to limestone progressively increases with age in carbonate rocks. This secular trend probably either reflects the earlier existence of geochemical settings that were more favourable to dolomitization or is the logical result of the fact that the likelihood for a limestone to undergo dolomitization increases proportionally with its age.
What is limestone made of?
Limestone is mostly made up of the mineral calcium carbonate (CaCO3) . This is not very soluble, so rocks don't dissolve very quickly. But if you add an acid, you add hydrogen ions (H+), which will react with the carbonate to form hydrogen carbonate HCO3- ions, which are very soluble in water, and the limestone will dissolve. Or, if there is more acid, two hydrogen ions will react with a carbonate to form carbonic acid - H2CO3 - which will decompose to form carbon dioxide - CO2 - which eventually bubbles off into the atmosphere, and water H2O.
What happens when hydrogen ions react with carbonate?
Or, if there is more acid, two hydrogen ions will react with a carbonate to form carbonic acid - H2CO3 - which will decompose to form carbon dioxide - CO2 - which eventually bubbles off into the atmosphere, and water H2O.
Definition
Geology
- Most carbonate rocks were deposited from seawater. These sedimentary carbonate rocks are common on every continent and have formed through most of geologic history; they are still forming today in the tropics as coral reefs and at the bottoms of shallow seas. Most of the limestone that is mined is crushed for aggregate. The majority of U.S. crushed stone production …
Formation
- Marine limestone forms because seawater has high concentrations of two key dissolved chemicals-calcium (Ca++) and bicarbonate (HCO3-) ions. In the near-surface layer of most oceans, corals, clams, and other sea-dwelling creatures use these two chemicals to make protective shells by combining them to form calcite or \"aragonite,\" which is the same chemical …
Cost
- In large parts of the United States there are extensive deposits of marine limestone of various ages from a few thousand to more than 350 million years old. Some deposits have chemical grades as high as 95% CaCO3. However, some areas are completely without any suitable limestone deposits. Most of the cost of limestone to the customer is determined by how far awa…
Uses
- Limestone has many industrial uses and can be used as mined or processed into a wide variety of products. It is the raw material for a large variety of construction, agricultural, environmental, and industrial materials. Powdered limestone is used to remove impurities from molten metals like steel. It can also remove toxic compounds from the exhaust of coal-burning power plants. Limes…
Other uses
- Limestone is also the raw material for making lime (CaO) that is used to treat soils, purify water, and smelt copper. Lime has many additional uses in the chemical industries.
Future
- Establishing new limestone quarries and cement plants in the United States is a slow process, and supply shortfalls require time to correct. It takes about 2 years to build a new cement plant, and the permitting process can take much longer - 8 to 10 years. Perhaps an even more challenging problem is that people may not welcome new quarries and plants to their area. In sp…
Advantages
- Limestone is most often mined from a quarry. However, underground limestone mines are found at places in the central and eastern United States, especially in and near cities. Underground mining of limestone has some advantages over surface quarrying and will probably increase in the future. Typical public concerns about limestone mining include dust, noise, blasting vibration, an…
Issues
- Some limestones are also aquifers, that is, they are rock units that can yield water to wells. Where limestone is an aquifer, there can be concerns that contaminants from the quarrying operations could escape into the groundwater.
Resources
- Limestone is among our Nation's most essential resources. Our understanding of that resource as an industrial mineral is poor given its importance to our economy. Because limestone has been regarded as a \"common\" rock, earlier geologic research was limited in scope. In the past, most USGS research on limestone has focused on mapping deposits, as well as understanding their r…
Industry
- Both geologic and economic limits will certainly affect future supplies of limestone. The United States presently consumes between 5 and 10% of the global production of industrial limestone. In 2007, domestic production of industrial limestone was about 1.3 billion metric tons, valued at more than $25 billion. In the same year, the Nation imported about 430,000 metric tons of industrial li…
Mission
- Meeting the challenge of supplying America's needs for essential mineral commodities such as industrial limestone requires accurate and unbiased scientific data. The ongoing work of scientists with the USGS Mineral Resources Program provides the information crucial to the creation of sound policies that will help ensure future supplies of mineral resources.
Overview
Limestone (calcium carbonate CaCO3) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiologic…
Formation
Limestone forms when calcite or aragonite precipitate out of water containing dissolved calcium, which can take place through both biological and nonbiological processes. The solubility of calcium carbonate (CaCO3) is controlled largely by the amount of dissolved carbon dioxide (CO2) in the water. This is summarized in the reaction:
Description
Limestone is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Dolomite, CaMg(CO3)2, is an uncommon mineral in limestone, and siderite or other carbonate minerals are rare. However, the calcite in limestone often contains a few percent of magnesium. Calcite in limestone is divided into low-magnesium and high-ma…
Occurrence
About 20% to 25% of sedimentary rock is carbonate rock, and most of this is limestone. Limestone is found in sedimentary sequences as old as 2.7 billion years. However, the compositions of carbonate rocks show an uneven distribution in time in the geologic record. About 95% of modern carbonates are composed of high-magnesium calcite and aragonite. The aragonite needles in …
Limestone landscape
Limestone is partially soluble, especially in acid, and therefore forms many erosional landforms. These include limestone pavements, pot holes, cenotes, caves and gorges. Such erosion landscapes are known as karsts. Limestone is less resistant to erosion than most igneous rocks, but more resistant than most other sedimentary rocks. It is therefore usually associated with hills and downland, …
Uses
Limestone is a raw material that is used globally in a variety of different ways including construction, agriculture and as industrial materials. Limestone is very common in architecture, especially in Europe and North America. Many landmarks across the world, including the Great Pyramid and its associated complex in Giza, Egypt, were made of limestone. So many buildings in Kingston,
See also
• Coral sand
• In Praise of Limestone – Poem by W. H. Auden
• Kurkar – Regional name for an aeolian quartz calcrete on the Levantine coast
• Limepit – Old method of calcining limestone
Further reading
• Boynton, Robert S. (1980). Chemistry and Technology of Lime and Limestone. Wiley. ISBN 0471027715.
Formation
- Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal, and fecal debris. It can also be a chemical sedimentary rock formed by th...
Geology
- The limestone that makes up these cave formations is known as \"travertine\" and is a chemical sedimentary rock. A rock known as \"tufa\" is a limestone formed by evaporation at a hot spring, lake shore, or other area.
Composition
- Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, clay minerals, pyrite, siderite, and other minerals. It can also contain large nodules of chert, pyrite, or siderite.
Properties
- The calcium carbonate content of limestone gives it a property that is often used in rock identification - it effervesces in contact with a cold solution of 5% hydrochloric acid.
Names
- There are many different names used for limestone. These names are based upon how the rock formed, its appearance or its composition, and other factors. Here are some of the more commonly used varieties.
Uses
- Limestone is a rock with an enormous 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 and used as a construction material. It is used as a crushed stone for road base and railroad ballast. It is used as an aggregate in concrete. It is fired in a kiln with crushed shale to make cement. Some additional b…
Advantages
- 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, crusher…
Other uses
- 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.
Availability
- Limestone is not found everywhere. It only occurs in areas underlain by sedimentary rocks. Limestone is needed in other areas and is so important that buyers will pay five times the value of the stone in delivery charges so that limestone can be used in their project or process.