Kalzit

Kalzit, known in English as calcite, is a carbonate mineral with the chemical formula CaCO3. It is one of the most common minerals in the Earth's crust and a primary constituent of limestone and marble. Calcite forms in the trigonal crystal system, typically as rhombohedra or scalenohedra, and shows cleavage in three directions. It is usually colorless or white but can be tinted by impurities, resulting in a wide range of colors. Calcite has a Mohs hardness of 3 and a typical specific gravity around 2.7. It is notable for its optical properties, being highly birefringent and uniaxial, which makes it useful in polarization experiments. Transparent varieties, such as Iceland spar, are used in optical instruments including Nicol prisms.

Occurrence and formation: Calcite forms by precipitation from calcium-rich waters in sedimentary environments and in hydrothermal veins. It crystallizes during diagenesis and metamorphism of carbonate rocks, producing rocks such as marble. As the primary mineral in limestone and marble, it occurs widely in carbonate-rich settings around the world.

Reactivity and varieties: Calcite effervesces with dilute acids, releasing carbon dioxide. It has several varieties and polymorphs, and is commonly associated with other calcium carbonate minerals such as aragonite and vaterite.

Uses: Calcite is a major source of lime and Portland cement and provides calcium carbonate for industries including paper, plastics, and agriculture. It is also collected as a geological specimen and, in some forms, used as a decorative stone.