Natural zeolites occurrs only in small amounts inside volcanic rock cavities. They are associated with the alteration of volcanic tuffs in saline, alkaline lake deposits and open hydrologic systems. Zeolites are distinguished by differences in their chemical compositions and the size and arrangement of their crystal structures. Clinoptilolite is the most commonly mined natural zeolite, followed by chabazite and mordenite.

The best way to characterise the zeolite is by X ray diffraction technique and compare the spectra with that published in zeolite atlas. If your sample is a powder, probably is a synthetic one.

Thank you very much Dr. Nelson Velasco and Mr. Om Prakash Kaptan

Actually some zeolites occur both naturally and synthetically. In this case an X-ray diffraction cannot discriminate the two possible occurences. Usually synthetic zeolites have a simpler composition than the natural ones; occurence of minor elements can be taken as an almost sure proof of natural origin.

Thank you very much Professor Ferraris

Dear Rashad

Commonly pure zeolite concentrates sold as powders are synthetic, whereas natural ones may include additional natural impurities (e.g. calcite, albite, quartz etc). Check your material by XRD for these natural compounds.

We worked on characterization of different commercial materials and natural zeolitic tuffs from Turkey. My answer was just a practical approach for discrimination.

From the practical point of view and in the case in question, Giovanni's answer is quite correct. However, X-ray diffraction should not be ruled out as it may be the quickest way to resolve the case. For instance, if the sample has a cubic symmetry, you can be sure it's a synthetic product (most likely of the FAU variety), natural crystals of the same (or similar) structural variety are extremely rare and do not occur in more than microgram amounts. To a certain extent this is also valid for hexagonal crystals. My suggestion would therefore be that of obtaining an X-ray powder pattern and compare it with the zeolite data bank in order to obtain the pertinence to the structural variety (identified with a three letter code). Several of these structural varieties occur only as synthetic products, others are also present in nature. However, of these latter ones, only a handful occur in large enough amounts to be mined and used for industrial purposes. It should therefore not be difficult to come up with the right answer in a very short time and without resorting to complicated analytical procedures for the determination of the component elements. This could in fact be the last resource (and a final one at that).

P.S. it goes without saying that all the relevant Zeoite data I mentioned above (Atlas of structure types, Collection of simulated powder patterns, etc.), can be found at: http://www.iza-structure.org/databases/

R.R.

If it is not in powder form then under a microscope other minerals that are associted naturally with zeolites should be observable. Zeolites also occur in metamorphic rocks as well as igneous so there is a good range of possible associated minerals. These would not occur with synthetic zeolites. This would be the easiest cheapest approach. If that fails an EDS (relatively inexpensive could provide some quick chemical information. Chemical analysis would not only show minor elements that should distinguish them but would immediately show elements used in doped zeolites that would have very unusual compositions not found in nature.