Gehlenite
Diffraction data computed using the structute from the paper listed below,
along with the cell parameters refined from single crystal data of R070478
      Louisnathan S J
      The Canadian Mineralogist 10 (1971) 822-837
      Refinement of the crystal structure of a natural gehlenite, Ca2Al(Al,Si)2O7
      Locality: Crestmore, California, USA

      CELL PARAMETERS:   7.7240  7.7240  5.0660   90.000   90.000   90.000
      SPACE GROUP: P-42_1m   

           ATOM        X         Y         Z     OCCUPANCY  ISO(B)
            Ca     0.33750   0.16250   0.51100     1.000     1.738
            Al     0.00000   0.00000   0.00000     0.930     1.020
            Mg     0.00000   0.00000   0.00000     0.050     1.020
            Fe     0.00000   0.00000   0.00000     0.020     1.020
            Al     0.14310   0.35690   0.95280     0.490     0.898
            Si     0.14310   0.35690   0.95280     0.510     0.898
            O      0.50000   0.00000   0.18840     1.000     2.027
            O      0.14180   0.35820   0.28320     1.000     1.692
            O      0.08720   0.17060   0.80330     1.000     1.778

            X-RAY WAVELENGTH:     1.541838
            BOUNDS ON TWO THETA:    0.0  90.0
            LIMITS IMPOSED ON THE INDICES ARE:  +/-  7 +/-  7 +/-  4
            MAX. ABS. INTENSITY / VOLUME**2:      21.20397220    
            The INTENSITY cut off value is   1.00

               2-THETA      INTENSITY    D-SPACING   H   K   L
                16.23          5.43        5.4617    1   1   0
                17.51          2.56        5.0660    0   0   1
                20.97          2.95        4.2361    1   0   1
                23.03          1.43        3.8620    2   0   0
                23.96         18.26        3.7142    1   1   1
                25.79          2.58        3.4543    2   1   0
                29.07         21.41        3.0713    2   0   1
                31.34        100.00        2.8540    2   1   1
                32.80          5.02        2.7308    2   2   0
                35.44          3.36        2.5330    0   0   2
                36.80         16.97        2.4425    3   1   0
                37.36          7.63        2.4069    1   0   2
                37.41          9.02        2.4038    2   2   1
                39.20          3.49        2.2979    1   1   2
                39.25          8.73        2.2953    3   0   1
                41.02          1.65        2.2002    3   1   1
                44.35          9.84        2.0427    2   1   2
                46.00          2.30        1.9731    3   2   1
                47.06          8.26        1.9310    4   0   0
                48.60          4.33        1.8733    4   1   0
                49.05          2.56        1.8571    2   2   2
                50.11          9.00        1.8206    3   3   0
                52.01         24.45        1.7582    3   1   2
                52.05          7.47        1.7571    4   1   1
                53.02          6.09        1.7271    4   2   0
                53.48          3.30        1.7133    3   3   1
                56.24          2.09        1.6357    3   2   2
                57.09          1.38        1.6133    1   1   3
                61.08          8.30        1.5171    2   1   3
                62.86          1.78        1.4783    3   3   2
                64.17          1.90        1.4513    5   1   1
                64.93          3.89        1.4363    2   2   3
                65.40          1.59        1.4270    4   2   2
                66.18          1.45        1.4120    3   0   3
                67.42          1.85        1.3890    3   1   3
                67.92         10.20        1.3801    5   2   1
                68.75          3.61        1.3654    4   4   0
                71.08          1.22        1.3262    3   2   3
                71.54          1.13        1.3189    4   3   2
                71.57          1.21        1.3184    4   4   1
                73.58          3.58        1.2873    6   0   0
                74.99          1.36        1.2665    0   0   4
                75.85          4.40        1.2543    4   1   3
                76.29          1.22        1.2481    5   2   2
                77.02          1.01        1.2381    3   3   3
                77.50          1.34        1.2317    6   1   1
                80.98          1.60        1.1873    6   2   1
                82.14          2.23        1.1735    5   4   1
                84.40          2.09        1.1476    6   0   2
                85.43          1.17        1.1364    3   0   4
                86.26          2.18        1.1276    5   1   3
                86.58          2.05        1.1243    3   1   4
                89.69          2.13        1.0932    5   2   3
================================================================================
       XPOW Copyright 1993 Bob Downs, Ranjini Swaminathan and Kurt Bartelmehs
  For reference, see Downs et al. (1993) American Mineralogist 78, 1104-1107.