Can you able to give me the chemical formula of calcite and aragonite? If you give me that,then only I will give you the JCPDS number and from that number you can get the reference spectra. I am also suggest you to download X-pert Highscore plus software for XRD. If you analyze your data in this software,then from that software you get the spectra. But that spectra is not perfect than JCPDS reference data. 

The chemical formula for both is CaCO3, they're two forms of the same material. I found the numbers 47-1743 for calcite and 41-1475 for aragonite but this is the first time I'm working with JCPDS data and I can't seem to get access to it.

I'll try out your advice, thanks!

Saskia- If you want those database,I will send you through mail. 

If you just need crystal structure files (.cif) to calculate your spectra, another option would be to search the Crystallography Open Database:

http://www.crystallography.net/index.php

The myncryst database is extremely complete and hhas always been very useful to me. See link below. From this database it is easy to get the data you need and eneter them in any software you want to use.

database.iem.ac.ru/mincryst/index.php

It is definitively not JCPDS but proper references are given.

Thanks everyone :)

It's unfortunate that JCPDS (now called PDF) is so expensive. I used to have access to it when I worked at a large synchrotron facility, but now that I am working at a University with a tight budget I cannot even get PDF for the x-ray facility! There are other free sources, but they are not nearly as complete as PDF.