What do you exactly mean by "quantify"? There are so many methods of quantification of molecules. Be specific Also, by XRD, do you mean x-ray diffraction? Questions must be posed well and clearly in order for others to answer them.

Read the following articles; useful on the measurement of Calcium Carbonate. XRD is also discussed.

Methods for Calcium Carbonate Content Measurement of Biocemented Soils

https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29MT.1943-5533.0002064

Characterization of Calcium Carbonate Polymorphs with Ca K Edge X-ray Absorption Fine Structure Spectroscopy

https://pdfs.semanticscholar.org/4fd8/22370724fc2069fe67e6cd6c7f68814d5867.pdf

Differentiating calcium carbonate polymorphs by surface analysis techniques—an XPS and TOF‐SIMS study

https://onlinelibrary.wiley.com/doi/pdf/10.1002/sia.2904

Best wishes

Thank you Dr. Vincente, Dr. Kenneth and Dr. Asit.

Hello, I agree, XRD using Rietveld refinements will tell you the percentages of all crystals phases present in the powder samples analysed by the XRD. e.g. 67% of Calcite, 22% of aragonite, 7% of feldspar, etc. However, it can only detect the crystalline structures. You could use FTIR/Raman to detect some of the other organic compounds in the samples and perhaps correlate the results with the XRD percentages.

You can also see this article:

http://www.mdpi.com/2075-163X/7/9/164/pdf

"Mineral Quantification with Simultaneous Refinement of Ca-Mg Carbonates Non-Stoichiometry by X-ray Diffraction, Rietveld Method"

It is a little specific, but it is fast and precise method.