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Gypsum

This page kindly sponsored by Dragon Minerals
Formula:
CaSO4 · 2H2O
System:
Monoclinic
Colour:
Colourless to white, ...
Hardness:
2
Name:
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 gemdat.org for gemological information about Gypsum.

Classification of Gypsum

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
7.CD.40

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
C : Sulfates (selenates, etc.) without additional anions, with H2O
D : With only large cations
Dana 7th ed.:
29.6.3.1
29.6.3.1

29 : HYDRATED ACID AND NORMAL SULFATES
6 : AXO4·xH2O
25.4.3

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

Geological Setting:
Commonest of the sulphate minerals, gypsum is found in marine evaporites, in caves where the air is dry enough to allow it to be deposited and remain, at fumaroles, and in the oxidized zones of sulfide deposits on occasion.

Physical Properties of Gypsum

Vitreous, Sub-Vitreous, Silky, Pearly, Dull
Diaphaneity (Transparency):
Transparent, Translucent, Opaque
Comment:
Wide range of luster based on varieties, pearly on {010}
Colour:
Colourless to white, often tinged other hues due to impurities; colourless in transmitted light..
Streak:
White.
Hardness (Mohs):
2
Hardness Data:
Mohs hardness reference species
Comment:
Hardness varies with direction down to 1.5
Tenacity:
Flexible
Cleavage:
Perfect
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}.
Fracture:
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].
Comment:
Also inelastic. Breakage depends on orientation.
Density:
2.312 - 2.322 g/cm3 (Measured)    2.308 g/cm3 (Calculated)

Crystallography of Gypsum

Crystal System:
Monoclinic
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°
Ratio:
a:b:c = 0.374 : 1 : 0.429
Unit Cell Volume:
V 495.15 ų (Calculated from Unit Cell)
Z:
4
Morphology:
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").
Twinning:
{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.
Comment:
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 www.smorf.nl.

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Crystal Structure

Structure
Reference
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.

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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:
d-spacingIntensity
7.63(100)
4.28(100)
3.80(20)
3.07(80)
2.87(50)
2.69(40)
2.22(20)
2.09(300

Optical Data of Gypsum

Type:
Biaxial (+)
RI values:
nα = 1.519 - 1.521 nβ = 1.522 - 1.523 nγ = 1.529 - 1.530
2V:
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:
Low
Dispersion:
Strong r > v inclined

Chemical Properties of Gypsum

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

Relationship of Gypsum to other Species

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.55SchieffelinitePb8(TeO4)5(SO4)3 · 8H2O
7.CD.60MontaniteBi2(TeO6) · 2H2O
7.CD.65OmongwaiteNa2Ca5(SO4)6 · 3H2O
25.4.1AnhydriteCaSO4
25.4.2BassaniteCaSO4 · 0.5H2O
25.4.4GlauberiteNa2Ca(SO4)2
25.4.5CesaniteNa3Ca2(SO4)3(OH)
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
25.4.12Ye'elimiteCa4Al6(SO4)O12
25.4.13EttringiteCa6Al2(SO4)3(OH)12 · 26H2O
25.4.14BentoriteCa6(Cr3+,Al)2(SO4)3(OH)12 · 26H2O
25.4.15CelestineSrSO4
25.4.16KalistrontiteK2Sr(SO4)2
25.4.17BaryteBaSO4

Other Names for Gypsum

Name in Other Languages:
Arabic:جص
Bulgarian:Гипс
Catalan:Guix
Croatian:Gips
Czech:Sádrovec
Danish:Gips
Dutch:Gips
Estonian:Kips
Hebrew:גבס
Hungarian:Gipsz
Japanese:石膏
Korean:석고
Latin:Gypsum
Latvian:Ģipsis
Lithuanian:Gipsas
Norwegian (Bokmål):Gips
Polish:Gips
Portuguese:Gipsita
Romanian:Gips
Russian:Гипс
Serbian (Cyrillic Script):Гипс
Simplified Chinese:石膏
Slovak:Sadrovec
Slovenian:Sadra
Swedish:Gips
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.
Electrical:
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:
Linnaeus (1736) Systema Naturae of Linnaeus (as Marmor fugax).

Delamétherie, J.C. (1812) Leçons de minéralogie. 8vo, Paris: volume 2: 380 (as Montmartrite).

Reuss (1869) Annalen der Physik, Halle, Leipzig: 136: 135.

Baumhauer (1875) Akademie der Wissenschaften, Munich, Sitzber.: 169.

Beckenkamp (1882) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 6: 450.

Mügge (1883) Neues Jahrbuch für Mineralogie, Geologie und Paleontologie, Heidelberg, Stuttgart: II: 14.

Reuss (1883) Akademie der Wissenschaften, Berlin (Sitzungsberichte der): 259.

Mügge (1884) Neues Jahrbuch für Mineralogie, Geologie und Paleontologie, 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, Leipzig: 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, Leipzig: 52: 223.

Kraus and Young (1914) Centralblatt für Mineralogie, Geologie und Paleontologie, 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, Leipzig: 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) Centralblatt für Mineralogie, Geologie und Paleontologie, 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, Carl (1929) Handbuch der Mineralogie. Berlin and Leipzig. 6 volumes: 1 [3B], 4274. (localities)

Ramsdell and Partridge (1929) American Mineralogist: 14: 59.

Josten (1932) Centralblatt für Mineralogie, Geologie und Paleontologie, Stuttgart: 432.

Parsons (1932) University of Toronto Studies, Geology Series, No. 32: 25.

Gallitelli (1933) Periodico de Mineralogia-Roma: 4: 132.

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.

Caspari (1936) Proceedings of the Royal Society of London: 155A: 41.

Terpstra (1936) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 97: 229.

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

Wooster (1936) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 94: 375.

Büssem and Gallitelli (1937) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 96: 376.

Gossner (1937) Forschritte der Mineralogie, Kristallographie und Petrographie, Jena: 21: 34.

Gossner (1937) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 96: 488.

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

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

Acta Crystallographica: B38: 1074-1077.

Bromehead (1943) 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.

Hardie, L.A. (1967), The gypsum-anhydrite equilibrium at one atmosphere pressure: American Mineralogist: 52: 171-200.

Gaines, Richard V., H. Catherine, W. Skinner, Eugene E. Foord, Brian Mason, Abraham Rosenzweig (1997), Dana's New Mineralogy : The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, 8th. edition: 598.

Sarma, L.P., P.S.R. Prasad, and N. Ravikumar (1998), Raman spectroscopy of phase transition in natural gypsum: Journal of Raman Spectroscopy: 29: 851-856.

Freyer, D. & Voigt, W. (2003): Crystallization and phase stability of CaSO4 and CaSO4-based salts. Monatshefte für Chemie, 134, 693-719.

S. Nazzareni, P. Comodi, L. Bindi, L. Dubrovinski (2010) The crystal structure of gypsum-II by single-crystal synchrotron X-ray diffraction data. American Mineralogist, 95, 655-658.

Internet Links for Gypsum

Specimens:
The following Gypsum specimens are currently listed for sale on minfind.com.

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.
Mineral and/or Locality  
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