University of Colorado

Mineral Structure Data

Amphibole Group

The amphibole group is composed of minerals of the general formula

The crystal structure of amphibole.

Orthoamphibole Unit Cells 


End-Member           Anthophyllite              Gedrite


Formula        (Mg5.53Fe1.47)(Na.5Ca.03)Si8O22(OH)2        (Fe 1.1Mg4.5Al1.2) (Al1.8Si6.3)O22(OH,F)2




Form.Wt.             827.23                     827.42
Density              3.111                      3.184
Mol Volume           265.88                     259.84

Z                    4                          4
Cryst.Sys.           Orthorhombic               Orthorhombic

Cryst.Class          mmm                        mmm
   
Space Group          Pnma                       Pnma

Cell Parameters
a(Å)                   18.560                     18.531
b(Å)                   18.013                     17.741   
c(Å)                   5.2818                     5.249   

Vol.                 1765.82                    1725.65

Reference             Finger                    Papike &
                      (1970)                    Ross (1970)

Thermal Expansion(Volumetric)
alpha         
a0  
a1 
a2 

Elastic Properties
Ks(GPa)        
G(Gpa)

Ortho-amphibole Octahedral Sites.


End-Member                       Anthophyllite                                             Gedrite

Site            M1           M2           M3           M4              M1           M2           M3           M4
C.N.            6            6            6            7               6            6            6            6
Occupant        Mg.96Fe.04     Mg.9 7Fe.03    Mg.97Fe.03     Mg.35Fe.65        Mg.88Fe.12    Mg.4Al.6    Mg .9Fe.1    Mg.55Fe.45

Point Sym.      1            1            m            1               1            1            m            1
Wyckoff Not.    8d           8d           4c           8d              8d           8d           4c           8d

Frac.Coord.
x              .12489        .12488       .12579       .12371          .1244        .1248        .1249        .1189
y              .16329        .07317        1/4        -.00982          .1611        .0731        1/4         -.0145
z              .3911        -.1099        -.1089        .3877          .3737        -.1281        -.1248      .3636

Distances
Mean           2.084         2.076         2.070       2.349           2.093        1.987        2.059        2.185
sigma           .032          .049          .011        .374            .042         .042         .035         .138

Poly.Vol.      11.877        11.765        11.595      17.281          11.923       10.379       11.274       12.766
Q.E.           1.0107        1.0094        1.0138        --            1.0171       1.0058       1.0222       1.0622
Ang.Var.       34.7          30.8          44.8          --            54.3         18.6         70.8         202.3

Site Energy    -1053.        -1201.        -1044.      -1071.          -1027.       -1906.       -1054.       -1059.
Model Charge   2.0           2.0           2.0         2.0             2.0          2.6          2.0          2.0

Ortho-amphibole Tetrahedral Sites.



End-Member                        Anthophyllite                                Gedrite

Site            T1A        T1B        T2A        T2B              T1A        T1B        T2A        T2B
C.N.            4          4          4          4                4          4          4          4
Occupant        Si         Si         Si         Si               Si.66Al.34    Si.62Al.38   Si        Si.84Al.16

Point Sym.      1          1          1          1                1          1          1          1
Wyckoff Not.    8d         8d         8d         8d               8d         8d         8d         8d

Frac.Coord.
x               .23039     .01863     .22731     .02469           .2315      .0202      .2278      .0266
y              -.1654     -.16626    -.07956    -.08177          -.1631     -.1645     -.0760     -.0802
z              -.4334      .2760      .0622     -.2227           -.4487      .2971      .0502     -.1985

Distances
Mean           1.620      1.622      1.624      1.633            1.650      1.656      1.616      1.649
sigma           .013       .011       .023       .020             .017       .009       .026       .017

Poly.Vol.      2.183      2.189      2.175      2.221            2.306      2.331      2.140      2.286
Q.E.           1.0002     1.0001     1.0076     1.0046           1.0006     1.0001     1.0087     1.0041
Ang.Var.       0.9        0.3        30.5       18.4             2.3        0.7        33.4       15.5

Site Energy    -4433.     -4403.     -4425.     -4393.           -3769.     -3701.     -4405.     -4062.
Model Charge   4.0        4.0        4.0        4.0              3.66        3.62       4.00       3.84
Mineral Data Base Index

GEOL 1010 Syllabus

GEOL 3010 Syllabus

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