Limestone is a natural natural stone, which is a soft sedimentary rock of organic or organo-chemical origin, consisting mainly of calcium carbonate (calcite). Often, it contains impurities of quartz, phosphate, silicon, clay and sand particles, as well as calcareous remains of the skeletons of microorganisms. In this article, we will examine in detail this natural material, its types, properties and scope, as well as find out what the chemical formula of limestone is, and much more.
Limestone formation
To begin, let's look at how these minerals formed. Limestone is mainly formed in shallow marine basins, although there is freshwater. It lies in the form of sediments and layers. Sometimes precipitated, like gypsum and salt, from the evaporating water of sea lagoons and lakes. However, most of it was deposited precisely in the seas, which did not experience intensive drying. The formation of most limestone rocks began with the release by living organisms of calcium carbonate from seawater to build skeletons and shells. These remains of deceased organisms in large quantities accumulate on the seabed. The most striking example of the extraction and accumulation of calcium carbonate are coral reefs. So, in some cases, at the fracture of the limestone rock, individual shells can be seen. Under the influence of the sea current and as a result of the influence of waves and surfs, reefs are destroyed. And on the seabed , calcium carbonate is added to the limestone debris , which precipitates from its saturated water. Calcite, which comes from destroyed ancient rocks, also participates in the formation of young limestone rocks.
Varieties
There are many types of limestones. A shell rock is usually called an accumulation of shells and their fragments, cemented into a cellular rock. In the case when the shells are very small, a soft, weakly bound, smearing, finely crumbling limestone is formed - chalk. The oolitic rock consists of miniature, fish-sized eggs, cemented balls. The core of each of them can be represented by a fragment of a shell, a grain of sand or any other particle of foreign material. In the case when the balls are larger, for example, with a pea, they are usually called pisoliths, and the rock, respectively, pisolite limestone. The next variety is travertine - it is formed on the surface during the precipitation of aragonite or calcite from the waters of carbon dioxide sources. If such deposits have a highly porous base (spongy), it is called tuff. An uncemented mixture of clay and calcium carbonate is called marl.
In addition, limestones can differ in color. The main color is white. But it can be yellowish, light beige, light gray, less often slightly pinkish. White-pink and white-yellow breed are considered the most valuable.
Limestone formula
As mentioned earlier, this natural material consists mainly of calcite or calcite residues of skeletons and shells, rarely of aragonite. So, the limestone formula will have the following form: CaCO 3 . However, pure rock is extremely rare, in some cases it includes various impurities of quartz, clay minerals, dolomites, gypsum, pyrite and, of course, organic residues. So, dolomitic limestone (the formula of this rock includes MgO) contains from four to seventeen percent of magnesium oxides, marly - up to 21 percent of acid oxides (SiO 2 + R 2 O 3 ). The composition of the carbonate may include dolomites CaMg (CO 3 ) 2 , FeCO 3 and MnCO 3 , in small quantities - oxides, sulfides and hydroxides Fe, Ca 3 (PO 4 ) 2 , CaSO 4 .
Limestone: properties and applications
The physicomechanical parameters of this rock are extremely heterogeneous, however, they directly depend on its texture and structure. High school students consider the properties of limestone (Grade 4) from the standpoint of its external characteristics. They study the following parameters: color, density, strength, condition, solubility. We will go a little further and examine in more depth these properties of the mineral. Limestone has a density in the range of 2700-2900 kg / m 3 . This variation is explained by the amount of impurities contained in quartz, dolomite and other minerals. Bulk mass varies much more. So, in travertines and shells it is only 800 kg / m 3 , and in crystalline rocks it reaches 2800 kg / m 3 . Considering the properties of limestone, it should be borne in mind that the compressive strength of the rock directly depends on its bulk density. So for shells, it is only 0.4 MPa, and for Afanites it approaches 300 MPa. The above rock characteristics also determine the use of these materials. For example, in construction, denser limestone is used for masonry walls, and porous is good for cladding and creating decorative ensembles.
Climate Impact
Depending on the level of humidity, the properties of limestone may vary. First of all, this affects its strength - it decreases markedly if the stone is wetted. In addition, most deposits are characterized by heterogeneity of the rock. At this point, it is worth paying special attention, since the density of the inhomogeneous material will vary, which, in turn, can lead to destruction. When analyzing the properties of limestone, one should not neglect such a parameter as frost resistance: this significantly affects the strength of the mineral and the duration of its use. So, in crystalline limestones, frost resistance is 300-400 cycles. However, this indicator is markedly reduced in the presence of cracks and pores in the material. Thus, all the mentioned properties of limestone must be taken into account when using this natural material in order to prevent its destruction.
Limestone in construction
The construction industry is the main consumer of the mineral under consideration. Dolomitized (rock) limestone is used for the production of putty and plaster mixtures, sealants and other things. White limestone in large quantities is used in the decoration and decoration of buildings. Shell rock is often found as building blocks, etc. We will not focus on this industry, it is already widely known to everyone. And therefore we go further.
Limestone in modern industrial production
It turns out that this natural material is used in the manufacture of paints and varnishes, rubbers and plastics. And purified from impurities harmful to the human body, it is used even in the food industry. The manufacture of glass is not possible without limestone, since it acts as the main source of calcium. This breed has become an indispensable, and most importantly, affordable component for paper production. In everyday life, we constantly use such products as pipes, linoleum, tiles, tiles, etc., and we are not aware that limestone is also present in all of these items. Even plastic production (PP, PVC, creplén, lavsans, etc.) can not do without this raw material. In paints, calcium carbonate is used as a coloring pigment. As you can see, this material occupies a leading position in almost all industries.
Chemical industry
Even things like shoe polish, toothpaste, cleaning powder, etc. that we use daily are derived from limestone. This raw material is also used in the manufacture of products used to protect the environment from various kinds of pollution. Based on the foregoing, we can safely say that the widely known and accessible material, which is limestone, is an essential element of modern civilization.
Interesting Facts
A great contribution to the development of stone carving was made by the peoples of South and Central America. Olmecs, Aztecs, Mayans achieved significant success in the ability to make weapons, cutting tools and other household items from chalcedony, obsidian and silicon. So, rolling pins, grain grains, mortars, etc. were created by them from basalt, sandstones and limestones. Impact and chopping tools were made from diorite, jadeite, jade and other materials. The main center for processing stone are considered Mayan cities - Tonin and Nebach.