Chalk– sedimentary rock is white, soft and friable, insoluble in water, organic (zoogenic) origin.
The basis of the chemical composition of calcium carbonate is chalk with a small amount of magnesium carbonate, but is normally present and a part of non-carbonate, mainly metal oxides. The chalk is usually a small admixture of tiny grains of quartz and microscopic calcite pseudomorphs on fossil marine organisms (radiolarians, etc.). Often there are large fossils of the Cretaceous period: belemnites, ammonites, and others.
Accumulations of chalk
Cretaceous stratigraphic unit of the European group occurred during the Cretaceous period. It forms the famous White Cliffs of Dover in Kent (England), and the white slopes on the other side of the Strait of Dover. In the city of Champagne (France) chalk caves used to store wine. Some of the highest chalk cliffs in the world are in Mons Klint (Denmark).
Ninety million years ago in northern Europe sludge accumulated at the bottom of the Great Sea. The simplest such as foraminifera, live in the marine debris that rains down from the upper layers of the ocean. These particles are made of calcite extracted from seawater.
Application of chalk and its analogs
Chalk – a necessary component of coated paper used in the printing industry for print quality illustrated books. Ground Chalk is widely used as a cheap material (pigment) for whitewashing, painting fences, walls, curbs to protect tree trunks from sunburn.
Chalk is widely used in the paint industry as a filler. Mel is not used as a pigment in paint (a white pigment is usually a titanium compound, a magnesium, zinc) because of the characteristic structure of chalk particles but used in the rubber, paper, in the sugar industry – for purification of beet juice for the production of binding agents (lime , Portland cement), in the glass industry, for the production of matches. In these cases, generally use t. N. Mel precipitated, chemically derived from calcium minerals. Chalk has been widely used as a particulate filler for polymeric compositions (polypropylene and polyethylene) Mel used for writing on big boards for general viewing (e.g. Sekolah) (molded school chalk 40% consists of chalk (calcium carbonate) and 60% of gypsum (calcium sulfate). it should be noted that the gastrointestinal agent is used, which is sometimes mistaken for chalk when X-ray studies, in fact also this slurry Vo desu Fata insoluble barium.