Cronstedtite
Diffraction data computed using the structute from the paper listed below,
along with the cell parameters refined from single crystal data of R061026
      Hendricks S B
      American Mineralogist 24 (1939) 529-539
      Random structures of layer minerals as illustrated by cronstedtite
      (2FeO.Fe2O3.SiO2.2H2O). Possible iron content of kaolin

      CELL PARAMETERS:   3.1770  3.1770 21.2900   90.000   90.000  120.000
      SPACE GROUP: R3        

           ATOM        X         Y         Z     OCCUPANCY  ISO(B)
            Si     0.00000   0.00000   0.03000     0.500     0.500
            Fe     0.00000   0.00000   0.03000     0.500     0.700
            Fe     0.00000   0.00000   0.83000     0.900     0.700
            O      0.00000   0.00000   0.11000     0.333     1.000
            OH     0.00000   0.00000   0.11000     0.667     1.000
            OH     0.00000   0.00000   0.54000     1.000     1.000
            O      0.50000   0.00000   0.00000     0.667     1.000

            X-RAY WAVELENGTH:     1.541838
            BOUNDS ON TWO THETA:    0.0  90.0
            LIMITS IMPOSED ON THE INDICES ARE:  +/-  2 +/-  2 +/- 19
            MAX. ABS. INTENSITY / VOLUME**2:      36.71371042    
            The INTENSITY cut off value is   1.00

               2-THETA      INTENSITY    D-SPACING   H   K   L
                12.47         18.03        7.0967    0   0   3
                25.10        100.00        3.5483    0   0   6
                32.82         39.70        2.7287    1   0   1
                33.64          5.31        2.6638    0   1   2
                36.77         69.62        2.4441    1   0   4
                38.04          4.18        2.3656    0   0   9
                38.97         33.94        2.3109    0   1   5
                44.40          5.67        2.0404    1   0   7
                47.53          7.32        1.9129    0   1   8
                51.51          1.79        1.7742    0   0  12
                54.50         28.43        1.6838    1   0  10
                58.07         19.91        1.5885    1   1   0
                58.29         10.91        1.5830    0   1  11
                59.65          2.88        1.5501    2  -1   3
                59.65          2.88        1.5501    1   1   3
                64.24          6.85        1.4498    2  -1   6
                64.24          6.85        1.4498    1   1   6
                65.80          1.73        1.4193    0   0  15
                68.33          8.64        1.3728    0   2   1
                68.81          2.74        1.3643    2   0   2
                70.73          8.35        1.3319    0   2   4
                70.79          9.29        1.3309    0   1  14
                71.55          4.04        1.3188    2  -1   9
                71.55          4.04        1.3188    1   1   9
                72.16          7.97        1.3091    2   0   5
                75.91          2.56        1.2534    0   2   7
                80.12          3.88        1.1979    1   0  16
                83.70          5.25        1.1555    0   2  10
                86.87          3.73        1.1213    2   0  11
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       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.