Hardystonite
Diffraction data computed using the structure from the paper listed below, 
along with the cell parameters refined from the powder pattern of R040026
      Louisnathan S J
      Zeitschrift fur Kristallographie 130 (1969) 427-437
      Refinement of the crystal structure of hardystonite, Ca2ZnSi2O7
      Locality: Franklin, New Jersey, USA

      CELL PARAMETERS:   7.8277  7.8277  5.0180   90.000   90.000   90.000
      SPACE GROUP: P-42_1m   

           ATOM        X         Y         Z     OCCUPANCY  ISO(B)
            Ca     0.33220   0.16780   0.50610     1.000     1.154
            Zn     0.00000   0.00000   0.00000     1.000     0.654
            Si     0.13930   0.36070   0.93940     1.000     0.468
            O      0.50000   0.00000   0.17710     1.000     1.749
            O      0.14000   0.36000   0.25510     1.000     1.130
            O      0.08180   0.18850   0.78470     1.000     1.740

            X-RAY WAVELENGTH:     1.541838
            BOUNDS ON TWO THETA:    5.0  90.0
            LIMITS IMPOSED ON THE INDICES ARE:  +/-  7 +/-  7 +/-  4
            MAX. ABS. INTENSITY / VOLUME**2:      22.78263453    
            The INTENSITY cut off value is   1.00

               2-THETA      INTENSITY    D-SPACING   H   K   L
                16.01          2.47        5.5350    1   1   0
                17.67         18.70        5.0180    0   0   1
                21.03          6.57        4.2245    1   0   1
                22.72          2.10        3.9139    2   0   0
                23.94         45.79        3.7176    1   1   1
                25.44          4.22        3.5007    2   1   0
                28.93         66.96        3.0861    2   0   1
                31.15        100.00        2.8711    2   1   1
                32.35         15.67        2.7675    2   2   0
                35.79          6.89        2.5090    0   0   2
                36.29         42.73        2.4753    3   1   0
                37.10         13.15        2.4234    2   2   1
                37.65          6.12        2.3893    1   0   2
                38.90          6.99        2.3150    3   0   1
                39.43          5.61        2.2852    1   1   2
                40.64         11.09        2.2199    3   1   1
                42.81          1.10        2.1122    2   0   2
                44.42         12.54        2.0393    2   1   2
                45.52          2.32        1.9925    3   2   1
                46.40          1.41        1.9569    4   0   0
                47.92          6.65        1.8985    4   1   0
                49.01         12.62        1.8588    2   2   2
                49.40          4.29        1.8450    3   3   0
                50.03          4.31        1.8232    4   0   1
                51.46          9.52        1.7757    4   1   1
                51.89         40.87        1.7621    3   1   2
                52.26         15.05        1.7503    4   2   0
                52.87          9.98        1.7317    3   3   1
                55.61          7.25        1.6527    4   2   1
                56.01          2.47        1.6417    3   2   2
                57.56          5.27        1.6012    1   1   3
                60.16          5.33        1.5381    2   0   3
                60.29          2.71        1.5351    5   1   0
                61.43          5.24        1.5092    2   1   3
                63.36          9.62        1.4680    5   1   1
                64.96          5.42        1.4355    4   2   2
                65.17          5.85        1.4315    2   2   3
                66.39          2.53        1.4082    3   0   3
                67.03          9.30        1.3962    5   2   1
                67.59          4.13        1.3859    3   1   3
                67.71          5.61        1.3838    4   4   0
                70.10          2.94        1.3424    5   3   0
                70.61          4.30        1.3340    4   4   1
                70.96          1.35        1.3282    4   3   2
                72.13          2.10        1.3095    5   1   2
                72.44          5.54        1.3046    6   0   0
                73.61          1.17        1.2869    6   1   0
                74.65          1.55        1.2715    4   0   3
                75.60          1.17        1.2577    5   2   2
                75.80          4.54        1.2550    4   1   3
                75.83          2.40        1.2545    0   0   4
                76.94          4.62        1.2392    3   3   3
                79.02          2.37        1.2117    4   4   2
                79.21          1.50        1.2093    4   2   3
                79.81          5.58        1.2017    6   2   1
                80.94          2.40        1.1877    5   4   1
                81.28          3.94        1.1837    5   3   2
                83.52          4.51        1.1575    6   0   2
                84.83          1.54        1.1430    4   3   3
                84.86          1.94        1.1426    2   2   4
                85.94          5.06        1.1310    5   1   3
                85.98          1.28        1.1306    3   0   4
                87.09          4.33        1.1190    3   1   4
                89.28          1.56        1.0972    5   2   3
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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.