Strontianite
Diffraction data computed using the structure from the paper listed below, 
along with the cell parameters refined from the powder pattern of R040037
      de Villiers J P R
      American Mineralogist 56 (1971) 758-767
      Crystal structures of aragonite, strontianite, and witherite

      CELL PARAMETERS:   5.0928  8.3654  6.0020   90.000   90.000   90.000
      SPACE GROUP: Pmcn      

           ATOM        X         Y         Z     OCCUPANCY  ISO(B)
            Sr     0.25000   0.41600   0.75690     1.000     0.508
            C      0.25000   0.76010  -0.08640     1.000     0.592
            O      0.25000   0.91190  -0.09460     1.000     0.913
            O      0.46940   0.68210  -0.08390     1.000     0.797

            X-RAY WAVELENGTH:     1.541838
            BOUNDS ON TWO THETA:    5.0  90.0
            LIMITS IMPOSED ON THE INDICES ARE:  +/-  4 +/-  7 +/-  5
            MAX. ABS. INTENSITY / VOLUME**2:      47.79600935    
            The INTENSITY cut off value is   1.00

               2-THETA      INTENSITY    D-SPACING   H   K   L
                20.42          4.45        4.3501    1   1   0
                21.24          1.86        4.1827    0   2   0
                25.29        100.00        3.5222    1   1   1
                25.96         52.63        3.4316    0   2   1
                29.77         12.17        3.0010    0   0   2
                31.43          1.99        2.8459    1   2   1
                31.68          9.91        2.8247    0   1   2
                34.70          6.55        2.5855    1   0   2
                35.25         15.72        2.5464    2   0   0
                35.50          2.54        2.5289    0   3   1
                36.37         24.36        2.4702    1   1   2
                36.75         27.57        2.4458    1   3   0
                36.86         12.09        2.4383    0   2   2
                39.94          2.15        2.2572    2   1   1
                41.52          9.72        2.1750    2   2   0
                43.26          2.95        2.0914    0   4   0
                44.30         40.93        2.0449    2   2   1
                45.95         18.42        1.9749    0   4   1
                46.79         15.95        1.9416    2   0   2
                47.99         27.36        1.8959    1   3   2
                50.19         22.30        1.8176    1   1   3
                50.57         10.50        1.8048    0   2   3
                50.89          1.70        1.7943    2   3   1
                51.92          3.65        1.7611    2   2   2
                53.40          2.43        1.7158    0   4   2
                55.21          2.01        1.6637    3   1   0
                56.98          1.77        1.6161    2   4   0
                57.48          8.70        1.6032    3   1   1
                58.03          1.01        1.5895    1   5   0
                59.21          8.28        1.5606    2   4   1
                60.23          8.19        1.5365    1   5   1
                61.83          1.40        1.5005    0   0   4
                62.93          1.08        1.4769    0   1   4
                63.14          3.14        1.4725    2   2   3
                63.99          2.70        1.4551    3   1   2
                64.24          4.34        1.4500    3   3   0
                64.45          1.23        1.4457    0   4   3
                65.61          2.88        1.4229    2   4   2
                65.84          3.80        1.4185    1   1   4
                66.16          1.65        1.4124    0   2   4
                66.57          2.59        1.4046    1   5   2
                67.14          2.23        1.3942    0   6   0
                72.38          7.62        1.3056    3   3   2
                73.22          3.28        1.2928    2   0   4
                74.12          7.11        1.2792    3   1   3
                74.13          7.04        1.2790    1   3   4
                74.53          3.25        1.2732    4   0   0
                75.13          3.36        1.2644    0   6   2
                75.64          6.46        1.2572    2   4   3
                76.55          6.10        1.2445    1   5   3
                77.24          1.02        1.2351    2   2   4
                78.16          5.62        1.2229    2   6   0
                80.46          4.02        1.1937    4   2   1
                82.26          1.72        1.1721    4   0   2
                82.54          3.89        1.1688    3   5   1
                83.55          3.36        1.1572    1   1   5
                83.85          1.47        1.1538    0   2   5
                84.90          2.88        1.1422    1   7   1
                85.80          3.10        1.1325    2   6   2
                86.17          1.44        1.1286    4   2   2
                87.56          1.20        1.1143    3   1   4
                88.23          1.37        1.1075    3   5   2
                89.03          1.12        1.0996    2   4   4
                89.91          1.18        1.0911    1   5   4
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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.