other names: Calcium carbonate
mineral class: Carbonates and nitrates
chemical formula: CaCO3
Chemical elements: Calcium, carbon, oxygen
Similar minerals: Calcite, aragonite
colour: pure limestone with white coloring
crystal structure: /
mass density: approx. 2.6
magnetism: not magnetic
Mohs hardness: approx. 3
stroke color: White
use: Building material
General to the limestone:
limestone describes a marine sedimentary rock that mainly consists of calcium carbonate consists. This chemical element can occur in limestone either as calcite or aragonite, accounting for up to 95 percent. In addition to the minerals calcite and aragonite limestone is also composed of small amounts of feldspar, quartz, dolomite, mica or various clay minerals. Limestone in its pure form is white in color, but various chemical impurities and admixtures lead to the rock also appearing in other shades. For example, limestone often becomes reddish by hematite, greenish by glauconite and chlorite, and gray by the addition of coal. Yellowish and brown discolorations are due to the presence of limonite or siderite. The rock, which is comparatively soft with a Mohs hardness of 3, has a porous structure and, depending on its formation and chemical composition, can occur in crystalline, shelled or granular form.
Occurrence and localities:
Limestone developed in marine waters 145 to 65 million years ago, especially in the Cretaceous from animals such as crabs, calcareous algae, corals, shells and arm-feet, which left behind lime-containing organic parts after dying. These deposited at the bottom and were gradually drained by the return of the sea. Over the course of millions of years, these deposits became increasingly dense and were slowly cemented to a stable mass under the action of minerals such as calcite, gypsum or dolomite. Even today, many limestones contain the fossil imprints of those living beings that served as source material.
Limestone is widespread around the world and is estimated to account for about ten percent of all sedimentary rocks. In Europe, he is one of the main rocks of the Alps to call. The so-called limestone Alps are, as their name already suggests, even mainly of limestone. This altogether more than six hundred kilometers long mountain range, which reaches from Austria to Slovenia and northern Italy (South Tyrol), is unmistakable due to the rugged peaks and gray karst walls. Also in Germany, Switzerland, France, Denmark, Sweden, Serbia, Croatia and Greece are large deposits of limestone. The state of Michigan is particularly important in the United States, and large deposits of limestone are found in Japan, China, Vietnam, Turkey, Tunisia and other North African countries.
History and use of limestone:
Kalkstein looks back on several millennia of history as an important building material. Even the ancient Egyptians built huge buildings from limestone. Among the most famous antiquity artefacts built from this material are the three pyramids of Giza. Today, limestone plays a minor role as a building material for facades and exterior cladding of buildings, as it reacts sensitively to acid rain and exhaust gases. The application of hydrochloric acid determines its authenticity, since it dissolves superficially on exposure to foam. Therefore, it is mainly used today as a material in the manufacture of tiles, floor slabs and wall coverings for indoor use. Economic importance also comes to him as an additive to toothpastes, glass, various paints and varnishes and cement.