Calcite

Frae Wikipedia
Lowp tae: navigation, rake
Calcite
Calcite.jpg
A ane-inch calcite rhomb that shaws the double image refraction property
General
Category Carbonate mineral
Formula
(repeating unit)
CaCO3
Strunz classification 05.AB.05
Crystal symmetry Trigonal 32/m
Unit cell a = 4.9896(2) Å, c = 17.0610(11) Å; Z=6
Identification
Color Colourless or white, an aa gray, yellae, green,
Crystal habit Crystalline, granular, stalactitic, concretionary, massive, rhombohedral.
Crystal seestem Trigonal hexagonal scalenohedral (32/m), Space Group (R3 2/c)
Twinnin Common bi fower twin laws
Cleavage Perfect on [1011] three directions wi angle o 74° 55'[1]
Fractur Conchoidal
Tenacity Brittle
Mohs scale hairdness 3 (definin mineral)
Luster Vitreous tae pearly on cleavage surfaces
Streak White
Diaphaneity Transparent tae translucent
Specific gravity 2.71
Optical properties Uniaxial (-)
Refractive index nω = 1.640 – 1.660 nε = 1.486
Birefringence δ = 0.154 – 0.174
Solubility Soluble in dilute acids
Ither characteristics Mey fluoresce reid, blue, yellae, an ither colours unner either SW an LW UV; phosphorescent
References [2][3][4]

Calcite is a carbonate mineral an the maist stable polymorph o calcium carbonate (CaCO3). The ither polymorphs are the minerals aragonite an vaterite. Aragonite will chynge tae calcite at 380–470°C,[5] an vaterite is even less stable.

References[eedit | eedit soorce]

  1. Klein, Cornelis and Cornelius S. Hurlbut, Jr., Manual of Mineralogy, Wiley, 20th, 1985, p. 329 ISBN 0-471-80580-7
  2. Mineral Data Publishers
  3. Calcite at Mindat
  4. Calcite at Webmineral
  5. S.Yoshioka and Y.Ktiano. "Transformation of aragonite to calcite through heating". DTA -TG study. Geochemical Journal Vol.19. Retrieved 31 March 2011.