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CaSO4 · 2H2O
Colourless to white, ...
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.

Classification of Gypsum

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

Gypsum in petrology

An essential component of (items highlighted in red)

Occurrences of Gypsum

Physical Properties of Gypsum

Vitreous, Sub-Vitreous, Silky, Pearly, Dull
Diaphaneity (Transparency):
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 (Mohs):
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 undergroes 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)

Crystallography of Gypsum

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 Volume:
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 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 Gypsum

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

Crystal Structure

Boeyens J C A Ichharam V V H (2002) Redetermination of the crystal structure of calcium sulphate dihydrate, CaSO4*2H2O Locality: synthetic. Zeitschrift fur Kristallographie 217:9-10.

Unit Cell | Structure | Polyhedra

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More Crystal Structures
Click here to view more crystal structures at the American Mineralogist Crystal Structure Database
X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:

Optical Data of Gypsum

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 Gypsum

CaSO4 · 2H2O
All elements listed in formula:
Analytical Data:
Slightly soluble in water. Soluble in HCl.

Relationship of Gypsum to other Species

Other Members of Group:
BrushiteCa(HPO4) · 2H2O
Churchite-(Y)Y(PO4) · 2H2O
PharmacoliteCa(HAsO4) · 2H2O
7.CD.05MatteucciteNaHSO4 · H2O
7.CD.10MirabiliteNa2SO4 · 10H2O
7.CD.15Lecontite(NH4,K)NaSO4 · 2H2O
7.CD.20HydroglauberiteNa10Ca3(SO4)8 · 6H2O
7.CD.25EugsteriteNa4Ca(SO4)3 · 2H2O
7.CD.30GörgeyiteK2Ca5(SO4)6 · H2O
7.CD.35Koktaite(NH4)2Ca(SO4)2 · H2O
7.CD.35SyngeniteK2Ca(SO4)2 · H2O
7.CD.45BassaniteCaSO4 · 0.5H2O
7.CD.50Zircosulfate(Zr,Ti)(SO4)2 · 4H2O
7.CD.60MontaniteBi2(TeO6) · 2H2O
7.CD.65OmongwaiteNa2Ca5(SO4)6 · 3H2O
25.4.2BassaniteCaSO4 · 0.5H2O
25.4.6EugsteriteNa4Ca(SO4)3 · 2H2O
25.4.7HydroglauberiteNa10Ca3(SO4)8 · 6H2O
25.4.8SyngeniteK2Ca(SO4)2 · H2O
25.4.9GörgeyiteK2Ca5(SO4)6 · H2O
25.4.10PolyhaliteK2Ca2Mg(SO4)4 · 2H2O
25.4.11Koktaite(NH4)2Ca(SO4)2 · H2O
25.4.13EttringiteCa6Al2(SO4)3(OH)12 · 26H2O
25.4.14BentoriteCa6(Cr3+,Al)2(SO4)3(OH)12 · 26H2O

Other Names for Gypsum

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

Other Information

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.
Not piezoelectric.
Thermal Behaviour:
Dehydrates and turns white.
Other Information:
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.

References for Gypsum

Reference List:
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 (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 (1909) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 46: 135.

Berek (1912) Jahrbuch Minerl., Beil.-Bd.: 33: 583.

Hutchinson and Tutton (1913) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 52: 223.

Kraus and Young (1914) Zentralblatt für Mineralogie, Geologie und Paläontologie, Stuttgart: 356.

Grengg (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 (1919) Bulletin de la Société française de Minéralogie: 42: 284.

Richardson (1920) Mineralogical Magazine: 19: 77.

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 and Tietze (1927) Die nutzbaren Mineralien, Stuttgart, 2nd. edition.

Foshag (1927) American Mineralogist: 12: 252.

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, et al (1936) Journal of the American Chemical Society: 58: 1261.

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 (1937) Journal of the American Chemical Society: 59: 2242.

de Jong and Bouman (1938) Zeitschrift für Kristallographie, Mineralogie und Petrographie: 100: 275.

Posnjak (1939) American Journal of Science: 35: 247.

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.

Huff (1940) Journal of Geology: 48: 641.

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.

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.

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 Gypsum URL:
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Localities for Gypsum

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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