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 skeletons of microorganisms. In this article, we will take a closer look at this natural material, its types, properties and scope, and also find out what the chemical formula of limestone is, and much more.
Limestone Formation
First, let's look at how these minerals were formed. Limestone is mainly formed in marine shallow basins, although there is also fresh water. It occurs in the form of deposits and layers. Sometimes it precipitates, like gypsum and s alt, from the evaporating sea water.lagoons and lakes. However, most of it was deposited in the seas, which did not experience intense drying. The formation of most limestone rocks began with the release of calcium carbonate by living organisms from sea water to build skeletons and shells. These remains of dead organisms accumulate in large quantities on the seabed. The most striking example of the extraction and accumulation of calcium carbonate are coral reefs. So, in some cases, individual shells can be seen at a break in limestone rock. Under the influence of the sea current and as a result of the impact of waves and surfs, reefs are destroyed. And on the seabed, calcium carbonate is added to the limestone fragments, which precipitates from the water saturated with it. Also, calcite, which comes from the destroyed ancient rocks, is involved in the formation of young limestone rocks.
Varieties
There are many types of limestone. It is customary to call a shell rock an accumulation of shells and their fragments cemented into a cellular rock. In the case when the shells are very small, a soft, loosely bound, smearing, finely crumbling limestone is formed - chalk. The oolitic rock consists of miniature, fish-egg-sized, 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 pisolites, and the rock, respectively, pisolite limestone. Nexta 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 unconsolidated mixture of clay and calcium carbonate is called marl.
In addition, limestones may differ in color. The main color is white. But it can also 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 remains of skeletons and shells, rarely of aragonite. This means that the limestone formula will look like this: CaCO3. 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 magnesium oxides, marl - up to 21 percent acid oxides (SiO2+R2 O3). The carbonate may include dolomites CaMg(CO3)2, FeCO3 and MnCO 3, in small quantities - oxides, sulfides and hydroxides of Fe, Ca3(PO4) 2, CaSO4.
Limestone: properties and applications
The physical and mechanical parameters of this rock are extremely heterogeneous, but directly depend on its texture and structure. Secondary 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 consider in more depth these properties of the mineral. Limestone has a density in the range of 2700-2900 kg/m3. This fluctuation is explained by the amount of impurities contained in quartz, dolomite and other minerals. The volumetric mass varies over a much larger range. So, for travertines and shell rocks, it is only 800 kg/m3, and for crystalline rocks it reaches 2800 kg/m3. Considering the properties of limestone, it should be taken into account that the compressive strength of the rock directly depends on its bulk density. So in shell rocks it is only 0.4 MPa, and in Afanites it approaches 300 MPa. The above characteristics of the rock determine the use of these materials. For example, in construction, denser limestone is used for laying walls, while porous limestone is good for cladding and creating decorative ensembles.
Impact of climatic conditions
Depending on the level of humidity, the properties of limestone may change. First of all, this affects its strength - it noticeably decreases if the stone is wetted. In addition, most deposits are characterized by rock heterogeneity. At this point, it is worth paying special attention, since a heterogeneous material will have a differentdensity, 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 noticeably 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 we are considering. Dolomitized (rock) limestone is used for the production of putty and plaster mixes, sealants and other things. White limestone is used in large quantities 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 so we move on.
Limestone in modern industrial production
It turns out that this natural material is used in the production of paints, rubbers and plastics. And purified from impurities harmful to the human body, it is used even in the food industry. Glass making is not possible without limestone, as itis the main source of calcium. This breed has become an indispensable, and most importantly, an affordable component for paper production. In everyday life, we constantly use such products as pipes, linoleum, tiles, tiles, etc., and we do not realize that limestone is also present in all these items. Even plastic production (PP, PVC, kremplens, lavsan, etc.) cannot do without this raw material. Paints use calcium carbonate 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, scouring powder, etc., which we use daily, are derivatives of 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 the most important element of modern civilization.
Interesting facts
The peoples of South and Central America made a great contribution to the development of stone carving. The Olmecs, Aztecs, Maya achieved significant success in the ability to make weapons, cutting tools and other household items from chalcedony, obsidian and silicon. So, rolling pins, grain grinders, mortars, etc. were created by them from bas alt, sandstones and limestones. Percussion and chopping tools were made from diorite, jadeite, jade and othermaterials. The main stone processing centers are the Mayan cities - Tonina and Nebach.
