As of 2000 there are 49 sets of inorganic and organic data files. Beach sand, you think it is quartz. Don't be to proud to ask the person who gave you the sample some questions about it's origin. In the case above, there is a residual. The residual turns out to be calcite.
H are the eight strongest lines in descending order.
Select the strongest unused line. Proceed to the main group. The patterns are arranged into subgroups based upon descending d-values of the either the second or third strongest lines. If a match is suspected, then the other eight d-values and intensities area checked to see if they are present in the observed pattern. Peaks with d-values outside the range of the main group can be found within the group.