Crystal structure of calcite

Trigonal crystal system; - RC; rhombohedral cell: ARH = 0.637 nm, a = 46 degrees 07'; Z = 2; if converted into hexagonal (double body center) lattice, then: ah = 0.499 nm, ch = 1.706 nm; Z = 6. [1] The structure of calcite type is summarized in Chapter 22 of Mineralogy.


The crystal structure of calcite can be derived from NaCl structure. It is assumed that the crystal structure of NaCl will be flattened along a cubic axis, the carbonate ions and Ca ions will be placed on the positions of Cl and Na ions which deform the NaCl structure respectively, and the planar triangular carbonate ions will be arranged vertically along the cubic axis, that is to say, the crystal structure of calcite (see figure [crystal structure of calcite]) will be in good condition. There are more than 600 kinds of polymers in various shapes. Columnar and parallel {0001} mainly developed in parallel [0001]


Developed planar and various states of rhombohedron or compound trigonometric polyhedron (Fig. H-1). Calcite often forms contact twins in accordance with (0001) and polycrystalline twins in accordance with (012). The orientation of polycrystalline twins on cleavage plane is different from that of dolomite (Fig. H-2). In nature, the appearance of polycrystalline twins can be used to explain that after the formation of calcite, it was subjected to geological stress.


Colorless or white, sometimes dyed light yellow, light red, purple, brown black by Fe, Mn, Cu and other elements. Colorless transparent calcite is called icespar. The cleavage {101} is complete; under the influence of stress, it slips along the direction of {01 2} polymer twin crystals and splits. Hardness 3. The relative density ranged from 2.6 to 2.9. Some calcites exhibit optical rotation.


Calcite is the most important rock-forming ore in the crust. English name: calcite, metamorphic rock, carbonate mineral, chemical composition: CaCO3, tripartite system, three groups of complete cleavage, fracture; glass luster, completely transparent to translucent, usually white or colorless, because of containing other metal chromogenic elements show light red, light yellow, light tea, rosy red, purple, a variety of colors, streak white, hardness 2.704-3.0, specific gravity 2.6-2.8, encounter severe rare hydrochloric acid. Foaming, a very pure and transparent crystal commonly known as Iceland Spar, has a strong birefringence and the greatest polarized light function, which can not be manufactured artificially and can not be replaced by natural crystals.