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CaSO4 · 2H2O
Colourless to white, often tinged other hues due to impurities; colourless in transmitted light..
Vitreous, Sub-Vitreous, Silky, Pearly, Dull
Specific Gravity:
2.312 - 2.322
Crystal System:
First known mention is by Theophrastus about 300-325 BCE from the Greek γυψοζ (gypsos) meaning plaster.
Isostructural with:
The most common sulphate mineral.
Found as both massive material, including the alabaster variety; and clear crystals, the selenite variety; and, parallel fibrous, the satin spar variety. Typically colourless to white, transparent crystals, thick tabular to lenticular, sometimes prismatic.

Visit for gemological information about Gypsum.

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Classification of GypsumHide

Approved, 'Grandfathered' (first described prior to 1959)

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
D : With only large cations
Dana 7th ed.:

6 : AXO4·xH2O

25 : Sulphates
4 : Sulphates of Ca, Sr and Ba

Pronounciation of GypsumHide

PlayRecorded byCountry
Jolyon & Katya RalphUnited Kingdom

Physical Properties of GypsumHide

Vitreous, Sub-Vitreous, Silky, Pearly, Dull
Transparent, Translucent, Opaque
Wide range of luster based on varieties, pearly on {010}
Colourless to white, often tinged other hues due to impurities; colourless in transmitted light..
Hardness Data:
Mohs hardness reference species
Hardness varies with direction down to 1.5
Perfect (eminent) and easy on {010}, almost micaceous in some samples; on {100} distinct, yielding a surface with a conchoidal fracture; on {011}, yielding a fibrous fracture {001}.
Splintery, Conchoidal
Translation gliding:
Readily undergoes translation gliding with T{010}, t{[001], which can also be generated by torsion about [001], or bending {010} about [010].
Also inelastic. Breakage depends on orientation.
2.312 - 2.322 g/cm3 (Measured)    2.308 g/cm3 (Calculated)

Optical Data of GypsumHide

Biaxial (+)
RI values:
nα = 1.519 - 1.521 nβ = 1.522 - 1.523 nγ = 1.529 - 1.530
Measured: 58° , Calculated: 58° to 68°
Max Birefringence:
δ = 0.010
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Strong r > v inclined

Chemical Properties of GypsumHide

CaSO4 · 2H2O

Crystallography of GypsumHide

Crystal System:
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 5.679(5) Å, b = 15.202(14) Å, c = 6.522(6) Å
β = 118.43°
a:b:c = 0.374 : 1 : 0.429
Unit Cell V:
495.15 ų (Calculated from Unit Cell)
Thin to thick tabular crystals, {010} with {111} and {120}; also prismatic [001], stout to acicular, with the prism zone often striated. Crystals may have warped surfaces or may be bent or twisted. Rosette-like clusters of lenticular crystals are common. Also found as granular masses, massive beds, and fibrous masses ("satin spar").
{100} ("swallow-tail"), very common, with a re-entrant angle formed ordinarily by {111}; on {101} as contact twins ("butterfly" or "heart-shaped"), along {111}; on {209}; also as cruciform penetration twins.
Data for I2/c cell (non-standard setting). There is another setting with space group C2/c and beta ~ 127°, and a further C2/c setting with a ~6.27, b ~15.20, c ~5.67 A, beta ~114°.

Crystallographic forms of GypsumHide

Crystal Atlas:
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Gypsum no.4 - Goldschmidt (1913-1926)
Gypsum no.23 - Goldschmidt (1913-1926)
Gypsum no.36 - Goldschmidt (1913-1926)
Gypsum no.52 - Goldschmidt (1913-1926)
Gypsum no.101 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by

Edge Lines | Miller Indicies | Axes

Opaque | Translucent | Transparent

Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation

X-Ray Powder DiffractionHide

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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:

Synonyms of GypsumHide

Other Language Names for GypsumHide

Norwegian (Bokmål):Gips
Serbian (Cyrillic Script):Гипс
Simplified Chinese:石膏
Traditional Chinese:石膏
Vietnamese:Thạch cao

Varieties of GypsumHide

AlabasterA fine-grained massive form of Gypsum .
OrditePseudomorphs of Gypsum after an unidentified mineral. [Clark, 1993 - "Hey's Mineral Index"].

Originally described from Orda, Permskaya Oblast', Middle Urals, Urals Region, Russia.
Satin Spar GypsumA fibrous variety of Gypsum. See also the main page on Satin Spar.
SeleniteThe name 'selenite' is mostly synonymous with gypsum but has been used historically to describe the transparent variety, as opposed to satin spar gypsum for the fibrous variety and alabaster for the fine-grained massive form.

The original name was giv...

Relationship of Gypsum to other SpeciesHide

Other Members of this group:
BrushiteCa(HPO4) · 2H2OMon. 2/m : B2/b
Churchite-(Y)Y(PO4) · 2H2OMon. 2/m : B2/b
PharmacoliteCa(HAsO4) · 2H2OMon. m

Common AssociatesHide

Associated Minerals Based on Photo Data:
Calcite260 photos of Gypsum associated with Calcite on
Quartz179 photos of Gypsum associated with Quartz on
Pyrite106 photos of Gypsum associated with Pyrite on
Siderite101 photos of Gypsum associated with Siderite on
Copper81 photos of Gypsum associated with Copper on
Dolomite80 photos of Gypsum associated with Dolomite on
Halite75 photos of Gypsum associated with Halite on
Fluorite62 photos of Gypsum associated with Fluorite on
Sulphur59 photos of Gypsum associated with Sulphur on
Azurite59 photos of Gypsum associated with Azurite on

Related Minerals - Nickel-Strunz GroupingHide

7.CD.Campostriniite(Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2OMon. 2/m : B2/b
7.CD.05MatteucciteNaHSO4 · H2OMon.
7.CD.10MirabiliteNa2SO4 · 10H2OMon. 2/m
7.CD.15Lecontite(NH4,K)NaSO4 · 2H2OOrth. 2 2 2 : P21 21 21
7.CD.20HydroglauberiteNa10Ca3(SO4)8 · 6H2OMon.
7.CD.25EugsteriteNa4Ca(SO4)3 · 2H2OMon.
7.CD.30GörgeyiteK2Ca5(SO4)6 · H2OMon.
7.CD.35Koktaite(NH4)2Ca(SO4)2 · H2OMon.
7.CD.35SyngeniteK2Ca(SO4)2 · H2OMon. 2/m : P21/m
7.CD.45BassaniteCaSO4 · 0.5H2OMon. 2 : B2
7.CD.50Zircosulfate(Zr,Ti)(SO4)2 · 4H2OOrth.
7.CD.55SchieffelinitePb10Te6+6O20(OH)14(SO4)(H2O)5Orth. mmm (2/m 2/m 2/m) : Cmcm
7.CD.60MontaniteBi2(TeO6) · 2H2O
7.CD.65OmongwaiteNa2Ca5(SO4)6 · 3H2OMon. 2 : B2

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

25.4.1AnhydriteCaSO4Orth. mmm (2/m 2/m 2/m)
25.4.2BassaniteCaSO4 · 0.5H2OMon. 2 : B2
25.4.4GlauberiteNa2Ca(SO4)2Mon. 2/m : B2/b
25.4.6EugsteriteNa4Ca(SO4)3 · 2H2OMon.
25.4.7HydroglauberiteNa10Ca3(SO4)8 · 6H2OMon.
25.4.8SyngeniteK2Ca(SO4)2 · H2OMon. 2/m : P21/m
25.4.9GörgeyiteK2Ca5(SO4)6 · H2OMon.
25.4.10PolyhaliteK2Ca2Mg(SO4)4 · 2H2OTric. 1
25.4.11Koktaite(NH4)2Ca(SO4)2 · H2OMon.
25.4.13EttringiteCa6Al2(SO4)3(OH)12 · 26H2OTrig. 3m : P3 1c
25.4.14BentoriteCa6(Cr3+,Al)2(SO4)3(OH)12 · 26H2OHex. 6/mmm (6/m 2/m 2/m) : P63/mmc
25.4.15CelestineSrSO4Orth. mmm (2/m 2/m 2/m) : Pnma
25.4.17BaryteBaSO4Orth. mmm (2/m 2/m 2/m) : Pnma

Fluorescence of GypsumHide

Common and varied. Most common colours of fluorescence are baby-blue and shades of golden yellow to yellow. Selenite crystals often exhibit zoned "hourglass" fluorescence in zones that may, or may not, be evident in ordinary light.

Other InformationHide

Not piezoelectric.
Thermal Behaviour:
Dehydrates and turns white.
Crystals containing impurities such as sand may exhibit "hourglass" shaped zones with and without the included matter. Cleavage plates may exhibit asterism when held up against a source of light.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
Plaster, plasterboard.

Gypsum in petrologyHide

An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.

References for GypsumHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Theophrastus (315 BC) Gypsum. in De Lapidibus, translated by Eichholz D E, 1965, Clarendon Press, Oxford: 83-85.
Agricola, G. (1546) Gypsum. in De Natura Fossilium translated by Bandy M C, Bandy J A 1955, Geological Society of America, New York, 89-93.
Linnaeus, C. (1736) Systema Naturae of Linnaeus (as Marmor fugax).
Delamétherie, J.C. (1812) Leçons de minéralogie. 8vo, Paris: volume 2: 380 (as Montmartrite).
Reusch, E. (1869) Die Körnerprobe am krystallisirten Gyps. Annalen der Physik: 136: 135-137.
Baumhauer (1875) Akademie der Wissenschaften, Munich, Sitzber.: 169.
Beckenkamp (1882) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 6: 450.
Mügge (1883) Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Heidelberg, Stuttgart: II: 14.
Reuss (1883) Sitzungsberichte der Akademie der Wissenschaften, Berlin: 259.[Reusch, E.?]
Mügge (1884) Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Heidelberg, Stuttgart: I: 50.
Des Cloizeaux (1886) Bulletin de la Société française de Minéralogie: 9: 175.
Dana, E.S. (1892) System of Mineralogy, 6th. Edition, New York: 933.
Auerbach, F. (1896) Annalen der Physik, Halle, Leipzig: 58: 357.
Viola (1897) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 28: 573.
Mügge (1898) Neues Jahrbuch für Mineralogie, Geologie und Paleontologie, Heidelberg, Stuttgart: I: 90.
Tutton, A.E.H. (1909) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 46: 135.
Berek (1912) Jahrbuch Minerl., Beil.-Bd.: 33: 583.
Hutchinson, A., Tutton, A.E.H. (1913) Uber die temperatur der optischen einaxigkeit von gyps. Zeitschrift für Kristallographie, Mineralogie und Petrographie: 52: 218-224.
Kraus and Young (1914) Zentralblatt für Mineralogie, Geologie und Paläontologie, Stuttgart: 356.
Grengg, R. (1914) Die Entwässerungsprodukte des gipses. Zeitschrift fur anorganische chemie: 90: 327-360.
Grengg, R. (1915) Mineralogische und petrographische Mitteilungen, Vienna: 33: 210.
Rosický (1916) Ak. Česká, Roz., Cl. 2: 25: No. 13.
Goldschmidt, V. (1918) Atlas der Krystallformen. 9 volumes, atlas, and text: vol. 4: 93.
Gaudefroy, C. (1919) Étude des figures de déshydratation à la surface des cristaux. Bulletin de la Société française de Minéralogie: 42: 284-380.
Richardson, W.A. (1920) The Fibrous Gypsum of Nottinghamshire. Mineralogical Magazine: 19: 77-95.
Gross (1922) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 57: 145.
Mellor, J.W. (1923) A Comprehensive Treatise on Inorganic and Theoretical Chemistry. 16 volumes, London: 3: 767.
Carobbi (1925) Ann. R. Osservat. Vesuviano [3]: 2: 125.
Dammer, B., Tietze, O. (1927) Die nutzbaren Mineralien, Stuttgart, 2nd. edition.
Foshag, W.F. (1927) The selenite caves of Naica, Mexico. American Mineralogist: 12: 252-255.
Himmel (1927) Zentralblatt für Mineralogie, Geologie und Paläontologie, Stuttgart: 342.
Matsuura (1927) Japanese Journal of Geology and Geography: 4: 65.
Nagy (1928) Zeitschrift für Physik, Brunswick, Berlin: 51: 410.
Berger, et al (1929) Akademie der Wissenschaften, Leipzig, Ber.: 81: 171.
Hintze, C. (1929) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1 [3B], 4274. [localities]
Ramsdell, L.S., Partridge, E.P. (1929) The crystal forms of calcium sulphate. American Mineralogist: 14: 59.
Josten (1932) Zentralblatt für Mineralogie, Geologie und Paläontologie, Stuttgart: 432.
Parsons (1932) University of Toronto Studies, Geology Series, No. 32: 25.
Gallitelli, P. (1933) Ricerche sul solfato di calcio semidrato e sull’anidrite solubile. Periodico di Mineralogia: 4: 132-171.
Gaubert (1933) Comptes rendus de l’Académie des sciences de Paris: 197: 72.
Beljankin and Feodotiev (1934) Trav. inst. pétrog. ac. sc. U.R.S.S., no. 6: 453.
Terpstra (1936) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 97: 229.
Weiser, H.B., Milligan, W.O., Ekholm, W.C. (1936) The mechanism of the dehydration of calcium sulfate hemihydrate. Journal of the American Chemical Society: 58: 1261-1265.
Wooster (1936) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 94: 375.
Büssem and Gallitelli (1937) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 96: 376.
Gossner (1937) Forschritte der Mineralogie, Kristallographie und Petrographie: 21: 34.
Gossner (1937) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 96: 488.
Hill, A.E. (1937) The transition temperature of gypsum to anhydrite. Journal of the American Chemical Society: 59: 2242-2244.
de Jong and Bouman (1938) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 100: 275.
Posnjak, E. (1938) The system, CaSO4-H2O. American Journal of Science, 5th Series: 35A: 247-272.
Tokody (1939) Ann. Mus. Nat. Hungar., Min. Geol. Pal.: 32: 12.
Tourtsev (1939) Bull. Académie of Sciences of the U.S.S.R., Ser. Geol., no. 4: 180.
Posnjak, E. (1940) Deposition of calcium sulfate from sea water. American Journal of Science: 238: 559-568.
Huff, L.C. (1940) Artificial helictites and gypsum flowers. Journal of Geology: 48: 641-659.
Pedersen, B.F., Semmingsen, D. (1982) Neutron diffraction refinement of the structure of gypsum, CaSO4·H2O. Acta Crystallographica: B38: 1074-1077.
Bromehead, C.E.N. (1943) The forgotten uses of selenite. Mineralogical Magazine: 26: 325.
Miropolsky and Borovick (1943) Comptes rendus de l’académie des sciences de U.R.S.S.: 38: 33.
Berg and Sveshnikova (1946) Bull. ac. sc. U.R.S.S.: 51: 535.
Palache, C., Berman, H., Frondel, C. (1951) The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 481-486.
Groves, A.W. (1958) Gypsum and Anhydrite, 108 p. Overseas Geological Surveys, London.
Gay, P. (1965) Some crystallographic studies in the system CaSO4—CaSO4.2H2O II. The hydrous forms. Mineralogical Magazine: 35: 354-362.
Hardie, L.A. (1967) The gypsum-anhydrite equilibrium at one atmosphere pressure. American Mineralogist: 52: 171-200.
Yamamoto, H., Kennedy, G.C. (1969) Stability relations in the system CaSO4-H2O at high temperatures and pressures. American Journal of Science, Schairer: 267-A: 550-557.
Tazaki, K., Mori, T., Nonaka, T. (1992) Microbial jarosite and gypsum from corrosion of Portland cement concrete. The Canadian Mineralogist: 30: 431-444.
Schofield, P.F., Knight, K.S., Stretton, I.C. (1996) Thermal expansion of gypsum investigated by neutron powder diffraction. American Mineralogist: 81: 847-851.
Gaines, R.V., Skinner, H.C.W., Foord, E.E., Mason, B., Rosenzweig, A. (1997) Dana's New Mineralogy: The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, 8th. edition: 598.
Sarma, L.P., Prasad, P.S.R., Ravikumar, N. (1998) Raman spectroscopy of phase transition in natural gypsum. Journal of Raman Spectroscopy: 29: 851-856.
Boeyens, J.C.A., Ichharam, V.V.H. (2002) Redetermination of the crystal structure of calcium sulphate dihydrate, CaSO4·2H2O. Zeitschrift für Kristallographie. New Crystal Structures: 217: 9-10.
Freyer, D., Voigt, W. (2003) Crystallization and phase stability of CaSO4 and CaSO4-based salts. Monatshefte für Chemie: 134: 693-719.
De la Torre, Á.G., López-Olmo, M.G., Álvarez-Rua, C., García-Granda, S., Aranda, M.A.G. (2004) Structure and microstructure of gypsum and its relevance to Rietveld quantitative phase analyses. Powder Diffraction: 19: 240-246.
Zimbelman, D.R., Rye, R.O., Breit, G.N. (2005) Origin of secondary sulfate minerals on active andesitic stratovolcanoes. Chemical Geology: 215: 37: 60.
Lane, M.D. (2007) Mid-infrared emission spectroscopy of sulfate and sulfate-bearing minerals. American Mineralogist: 92: 1-18.
Comodi, P., Nazzareni, S., Zanazzi, P.F., Speziale, S. (2008) High-pressure behavior of gypsum: A single-crystal X-ray study. American Mineralogist: 93: 1530-1537.
Buzgar, N., Buzatu, A., Sanislav, I.V. (2009) The Raman study on certain sulfates. Annalele Stiintifice ale Universitatii: 55: 5-23.
Nazzareni, S., Comodi, P., Bindi, L., Dubrovinski, L. (2010) The crystal structure of gypsum-II by single-crystal synchrotron X-ray diffraction data. American Mineralogist: 95: 655-658.
Rubbo, M., Bruno, M., Aquilano, D. (2011) The (100) Contact Twin of Gypsum. Crystal Growth & Design: 11(6): 2351-2357.
Rubbo, M., Bruno, M., Masaro, F.R., Aquilano, D. (2012) The five twin laws of gypsum (CaSO4·2H2O): A theoretical comparison of the interfaces of the penetration twins. Crystal Growth & Design: 12(6): 3018-3024.
Van Driessche, A.E.S., Benning, L.G., Rodriguez-Blanco, J.D., Ossorio, M., Bots, P., Gárcia-Ruiz, J.M. (2012) The role and implications of bassanite as a stable precursor phase to gypsum precipitation. Science: 336: 69-72.
Bishop, J.L., Lane, M.D., Dyar, M.D., King, S.J., Brown, A.J., Swayze, G.A. (2014) Spectral properties of Ca-sulfates: gypsum, bassanite, and anhydrite. American Mineralogist: 99: 2105-2115.
Ossorio, M., Van Driessche, A.E.S., Pérez, P., García-Ruiz, J.M. (2014) The gypsum-anhydrite paradox revisited. Chemical Geology: 386: 16-21.

Internet Links for GypsumHide

Localities for GypsumHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

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