Dolomite
Diffraction data computed using the structure from the paper listed below, 
along with the cell parameters refined from the powder pattern of R050129
      Antao S M, Mulder W H, Hassan I, Crichton W A, Parise J B
      American Mineralogist 89 (2004) 1142-1147
      Cation disorder in dolomite, CaMg(CO3)2, and its influence on the
      aragonite+magnesite - dolomite reaction boundary
      Sample: P = 3 GPa, T = 296 K

      CELL PARAMETERS:   4.8220  4.8220 16.0995   90.000   90.000  120.000
      SPACE GROUP: R-3       

           ATOM        X         Y         Z     OCCUPANCY  ISO(B)
            Ca     0.00000   0.00000   0.00000     1.000     2.985
            Mg     0.00000   0.00000   0.50000     1.000     2.985
            C      0.00000   0.00000   0.24220     1.000     3.000
            O      0.24700  -0.03800   0.24300     1.000     3.814

            X-RAY WAVELENGTH:     1.541838
            BOUNDS ON TWO THETA:    5.0  90.0
            LIMITS IMPOSED ON THE INDICES ARE:  +/-  3 +/-  3 +/- 14
            MAX. ABS. INTENSITY / VOLUME**2:      18.89222714    
            The INTENSITY cut off value is   1.00

               2-THETA      INTENSITY    D-SPACING   H   K   L
                21.99          2.00        4.0422    1   0   1
                24.01          5.19        3.7069    0   1   2
                30.86        100.00        2.8980    1   0   4
                33.39          4.32        2.6833    0   0   6
                35.20          6.00        2.5499    0   1   5
                37.30         10.56        2.4110    1   1   0
                41.04         18.45        2.1992    1   1   3
                41.04          5.71        2.1992    2  -1   3
                43.72          4.17        2.0706    0   2   1
                44.85         11.95        2.0211    2   0   2
                49.16          4.00        1.8534    0   2   4
                50.33         13.65        1.8129    0   1   8
                50.92          5.55        1.7934    1   1   6
                50.92         11.66        1.7934    2  -1   6
                51.06          1.25        1.7888    0   0   9
                58.78          1.52        1.5708    3  -1   1
                59.70          4.59        1.5489   -1   3   2
                59.70          1.62        1.5489    1   2   2
                63.29          2.77        1.4694    3  -1   4
                63.29          1.93        1.4694    2   1   4
                64.29          2.04        1.4490    2   0   8
                64.91          1.42        1.4366    2  -1   9
                65.91          1.38        1.4173   -1   3   5
                67.26          4.87        1.3920    3   0   0
                70.15          2.02        1.3416    0   0  12
                74.41          1.55        1.2750    0   2  10
                76.74          1.58        1.2419    1   2   8
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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.