University of Colorado

Mineral Structure Data

Hydroxide Group

The hydroxide group is composed of non-silicate minerals withOH as the principal polyanionic species.

The crystal structure of diaspore.


The crystal structure of brucite.



End-Member          Gibbsite          Diaspore          Boehmite          Brucite          Goethite

Formula Al(OH)3 AlO(OH) AlO(OH) Mg(OH)2 FeO(OH) Form.Wt. 78.004 59.988 59.988 58.327 88.854 Density 2.421 3.377 3.075 2.377 4.294 Mol Volume 32.222 17.862 19.507 24.524 20.693 Z 8 4 4 1 4 Cryst.Sys. Monoclinic Orthorhombic Orthorhombic Trigonal Orthorhombic Cryst.Class 2/m mmm mmm 3m1 mmm Space Group P21/n Pbnm Amam P3m1 Pbnm Cell Parameters a(Å) 8.684 4.401 3.693 3.142 4.587 b(Å) 5.078 9.421 12.221 3.142 9.937 c(Å) 9.736 2.845 2.865 4.766 3.015 beta 94.54 Vol. 427.98 117.96 129.30. 40.75 137.43 Ref. Saalfeld & Busing & Hill Zigan & Forsyth Wedde (1974) Levy (1958) (1981) Rothbauer(1967) et al.(1968)

Table 3.1.2. Hydroxide Cation Sites

End-Member          Gibbsite          Gibbsite          Diaspore          Boehmite          Brucite          Goethite

C.N. 6 6 6 6 6 6 Occupant Al(1) Al(2) Al Al Mg Fe Point Sym. 1 1 m mm 3m m Wyckoff Not. 4e 4e 4c 4c 1a 4c Frac.Coord. x 0.1679 0.3344 0.0451 0.25 0 0.0477 y 0.5259 0.0236 -0.1446 -0.3178 0 0.8539 z -0.0023 -0.0024 1/4 0 0 1/4 Distances O1 1.910 1.930 (2) 1.851 (2) 1.944 (6) 2.099 (2) 1.957 (1) 1.858 (2) 1.878 (1) 1.926 (2) 1.893 (2) 2.095 O2 1.922 1.922 (2) 1.975 (1) 1.980 O3 1.925 1.881 O4 1.906 1.890 O5 1.832 1.862 O6 1.918 1.947 Mean 1.902 1.905 1.915 1.905 2.099 2.021 sigma .035 .033 .067 .031 .000 .082 Poly.Vol. 9.019 9.061 9.100 9.000 12.039 10.667 Q.E. 1.0120 1.0120 1.0205 1.0164 1.0161 1.0226 Ang.Var. 42.5 42.5 64.0 52.0 52.0 69.2 Site Energy -2408. -2396. -2484. -2204. -1139. -2352.

Mineral Data Base Index

GEOL 1010 Syllabus

GEOL 3010 Syllabus

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