Calcite
Description
The most common crystalline form of Calcium carbonate. Calcite is widely distributed throughout the world as Chalk, Limestone, and Marble. Major deposits were formed from ancient sea beds and hard water deposits (e.g., stalactites). Iceland is famous for producing large clear birefractive calcite crystals that are used in optical systems (Iceland spar). In addition to clear colorless crystals, calcite may also appear white or pale shades of other colors depending on the crystal size and the presence of impurities. Marble is limestone that has been metamorphosed to form compact crystals of calcite. Calcite has been gathered or mined since Paleolithic times. In the form of chalk, calcite was powdered for use as a Pigment and as an ingredient in the manufacture of Steel, Cement, and Glass. Limestone and marble are used for sculpture and buildings.
Synonyms and Related Terms
calcium carbonate; marble; limestone; Iceland spar; dogtooth spar; dog-tooth spar; nailhead spar; satin spar; calcareous spar; calc spar; calcspar; calcite (It., Fr., Port.); Kalzit, Calcit (Deut.); calcita (Esp.); calciet (Ned.); calcium salt of carbonic acid; Pigment White 18; CI 7720
Risks
- ThermoFisher SDS
Physical and Chemical Properties
- Trigonal crystal system with granular, stalatitic, massive or rhombohedral crystals
- Perfect cleavage in three directions
- Fracture = conchoidal
- Luster = vitreous to pearly
- Streak = white
- Can doubly refract light
- Fluorescence = aged surfaces of calcite may fluoresce purple or blue in ultraviolet light; freshly cleaved surfaces are white to yellow; may be phosphorescent
- Reacts with acids to evolve carbon dioxide.
| Composition | CaCO3 |
|---|---|
| CAS | 471-34-1 |
| Mohs Hardness | 3.0 |
| Density | 2.71-2.72 g/ml |
| Molecular Weight | mol. wt. = 100.09 |
| Refractive Index | 1.486; 1.658; (1.566) |
| Birefringence | 0.154 - 0.174 (very high) |
Comparisons
Properties of Common Abrasives
Additional Images
Calcite at 100x (visible light left; UV light right)
Plane polarized light micrograph of calcite
Resources and Citations
- Gem Identification Lab Manual, Gemological Institute of America, 2016.
- R. Gettens, E. West Fitzhugh, R.Feller, "Calcium Carbonate Whites", Artists Pigments, Vol. 2., A. Roy ed. Oxford University Press, Oxford, 1993.
- Mineralogy Database: Calcite
- Encyclopedia Britannica, http://www.britannica.com Comment: "calcite" [Accessed December 4, 2001]
- R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 138, Mohs=3
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
- Thomas Gregory, The Condensed Chemical Dictionary, Reinhold Publishing, New York, 3rd ed., 1942 Comment: Mohs =2
- Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976 Comment: Mohs=3
- Wikipedia: Calcite (Accessed Sept 2 2005 and Dec 2022) hardness = 3, sp = 2.7
- Jack Odgen, Jewellery of the Ancient World, Rizzoli International Publications Inc., New York City, 1982
- A.Lucas, J.R.Harris, Ancient Egyptian Materials and Industries, Edward Arnold Publishers Ltd., London, 4th edition, 1962