University of Colorado

Mineral Structure Data

Humite Group

The Humite group is composed of minerals of the general formula (Mg,Fe)2x+1(SiO4)x(F,OH)2 where x = 1 (norbergite), 2 (chondrodite), 3 (humite), and 4 (clinohumite). In natural samples Mg>>FE and F>>OH. The principal occurrence is in high grade metamorphosed mafic and ultramafic rocks.

The crystal structure of humite.

The crystal structure of clinohumite. 

End-Member      Norbergite            Chondrodite           Humite                Clinohumite
Formula         (Mg,Fe)3SiO4(F,OH)2   (Mg,Fe)5(SiO4)2(F,OH)2  (Mg,Fe)7(SiO4)3(F,OH)2 (Mg,Fe)9(SiO4)4(F,OH)2  


Form.Wt.        203.016               341.73                482.44                640.49
Z               4                     2                     4                     2
CrystalSystem   Orth                  Mono                  Orth                  Mono
PointGroup      mmm                   2/m                   mmm                   2/m
SpaceGroup      Pbnm                  P21/b                 Pbnm                  P21/b

UnitCell
a(Å)            4.7104                4.7284                4.7408                4.7441
b(Å)            10.2718               10.2539               10.2580               10.2501   
c(Å)            8.7476                7.7404                20.8526               13.6635   
alpha                                 109.059                                     100.786
Vol(Å3)         423.25                359.30                1014.09               652.68

MolarVol        63.73                 108.20                152.70                196.55
Density         3.186                 3.158                 3.159                 3.258

Thermal Expansion(Volumetric)
alpha         
a0  
a1 
a2 

Elastic Properties
Ks(GPa)        
G(Gpa)
Mineral Data Base Index

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