Smithsonite
Diffraction data computed using the structure from the paper listed below, 
along with the cell parameters refined from the powder pattern of R040051
      Graf D L
      American Mineralogist 46 (1961) 1283-1316
      Crystallographic tables for the rhombohedral carbonates

      CELL PARAMETERS:   4.6560  4.6560 15.0540   90.000   90.000  120.000
      SPACE GROUP: R-3c      

           ATOM        X         Y         Z     OCCUPANCY  ISO(B)
            Zn     0.00000   0.00000   0.00000     1.000     0.700
            C      0.00000   0.00000   0.25000     1.000     0.300
            O      0.27640   0.00000   0.25000     1.000     1.000

            X-RAY WAVELENGTH:     1.541838
            BOUNDS ON TWO THETA:    5.0  90.0
            LIMITS IMPOSED ON THE INDICES ARE:  +/-  3 +/-  3 +/- 13
            MAX. ABS. INTENSITY / VOLUME**2:      62.83165574    
            The INTENSITY cut off value is   1.00

               2-THETA      INTENSITY    D-SPACING   H   K   L
                25.05         51.15        3.5543    0   1   2
                32.54        100.00        2.7513    1   0   4
                38.68         26.12        2.3280    1   1   0
                42.82         12.68        2.1118    1   1   3
                46.64         21.97        1.9475    2   0   2
                51.42         13.05        1.7772    0   2   4
                53.71         31.37        1.7065    1   1   6
                53.76         19.59        1.7052    0   1   8
                61.12          1.26        1.5163    2   1   1
                62.14         14.83        1.4937    1   2   2
                66.15         12.23        1.4126    2   1   4
                66.27          3.48        1.4103    1   0  10
                68.17          5.04        1.3756    2   0   8
                69.16          1.61        1.3584    1   1   9
                70.00         10.40        1.3441    3   0   0
                75.83          3.24        1.2545    0   0  12
                79.45          3.36        1.2062    0   2  10
                81.22          6.20        1.1843    1   2   8
                88.54          3.97        1.1044    1   1  12
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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.