kalcyt
Kalcyt, known in English as calcite, is a widely distributed mineral composed of calcium carbonate (CaCO3). It is the most stable polymorph of calcium carbonate at Earth's surface and occurs in a broad range of geological settings, including sedimentary rocks such as limestone, metamorphic marble, and hydrothermal veins. Calcite crystallizes in the trigonal crystal system and commonly forms rhombohedral crystals; it also occurs as granular masses and less commonly as transparent prisms. Cleavage is perfect in three directions, producing rhombohedra. The hardness on the Mohs scale is 3, and the specific gravity is about 2.71. The mineral’s luster ranges from vitreous to pearly, and its color is highly variable, depending on impurities, from white and colorless to yellow, orange, pink, blue, or green. Calcite readily effervesces with dilute acids, a classic test for carbonate minerals, and it often displays strong birefringence under polarized light, which makes high-quality crystals such as Iceland spar useful in optical applications.
Calcite is a principal component of limestone and marble and is widely mined for cement and lime
The name kalcyt corresponds to calcite in several Slavic languages, deriving from the Latin calx, lime.