Arshad, these are not spectra. It is not a spectroscopic technique. Better referred to as diffractograms, patterns, or traces.

I have included a link to the ICDD tutorials page, you should find much helpful information here.

When identifying minerals it can help if you use a subfile to limit the range of the search, and, if you have it from XRF or EDS data, use a chemical filter to limit the possible number of matches. Initially you can also choose to display only high quality patterns that will reduce the number still further. 

However, it is often down to the investigator to make sense of the list that is presented. Yes, that means searching through the list! You need to be aware of what is likely and what is unlikely given knowledge of your own material. (I have seen reputable companies publish data that was nonsense just because it came at the top of the search list). Use it as a tool to guide you rather than an absolute answer.

http://www.icdd.com/resources/tutorials/

Thank you Ian for referring to the correct terminology and a useful link. I appreciate it!

I echo Ian's response, adding/emphasizing a few points.

*  Your theta–two-theta line scans (or traces, or diffractograms) must be carefully collected.  For using peaks to ID constituent phases, the following are extremely important:

  ** The sample height, z, must be set to exactly zero – otherwise your 2-theta values can shift, sometimes significantly depending upon your particular optics setup when collecting data.  Set z to zero by adjusting z until the direct beam is bifurcated.  Ask the lab's maintainer for help with this because improper procedure here can damage the detector.  Basically, (i) insert an appropriate attenuator in the optical path, and keep the shutter closed until you scan; (ii) set 2-theta to zero, meaning direct beam firing into the detector; (iii) If your instrument can do z-scans, then collect one that goes from zero to a consistent maximum.  If your instrument cannot do z-scans, then you will have to fiddle with the stage's z in iterations.  Either way, you next (iv) set the z to the value where the intensity is half of the maximum.  (v) Advanced users will follow this with an omega scan to ensure that the sample surface is in-plane with the zero-beam, and then repeat the z-scan and z-setting.  And for powder samples, some people mix-in some Al2O3 for TTH calibration.  (vi) AGAIN, DISCUSS THIS WITH YOUR LAB SUPERVISOR.

  **  ICDD software is under-cautious, so it returns far too many results by default.  Limit your search to the elements that you know are present in the sample.  It's in a menu and dialog box that are a pain to use, but you MUST do this.  I also echo and double-emphasize Ian's suggestion to select the "use only high-quality patterns" option.

  **  Use JADE™ if your lab has this software.   Also, refer during peak ID work to the International Crystal Structure Database (ICSD).  Your institution probably has online access.  ICSD is a database you refer to, but its dataset is far-better groomed and maintained than that of the ICDD and its peak-ID functionality (which is better than resorting to the Hanawalt tables by hand).

  **  Read the ICDD cards for the phases that the software identifies.  They have notes on the data-collection, as well as a reference to the original work.  The most common error people make is to NOT do this.  The notes will have details such as, "high-pressure phase", "collected at 79 K", or other pertinent info.  If it's not a room-temperature phase, per the card, cross it off of your list. . .  at least at first.

  **  Last, echoing Ian again, proper ID is up to the investigator.  Think about the composition and thermal history of the sample.  Look at the thermodynamics.  Look up the appropriate phase diagrams for the identified materials, and make sure that there is a tie-line between them (unless the sample was quenched from sintering temperature).

That should be enough to get you started.  Material ID takes practice, calibrated and aligned data-collection, and careful reflection if you want reliable results.  Good luck!

Thanks Mark for the details you outlined in response to my query. I appreciate it!