A Collectors Perspective

Zeolites have a often  surprising morphology. Some species are very variable in appearance. Thomsonite for example builds fine fibers aggregated to waxy hemispheres, long prismatic crystals, thin tabular crystals and blocky forms. Very different in appearance and visually almost impossible to recognize as the same species. On the other side, different species like the Stilbite series, Stellerite and Barrerite look almost the same and can only distinguished by sophisticated analytical methods. The morphology of zeoltes is complicated by twinning like the Chabazite-series and the Phillipsite-series and Harmotome to minerals very variable in one way and very similar also. Further complication is caused by zonar structures. So it can be, that one crystal host different species of identical or different crystal frameworks. The latter is the case with epitaxial crystal growths, which are common for zeolites and observed as cause  for very unusual looking aggregates. This epitaxys can be sub microscopic or distinct visible.

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Pictures are different forms of Thomsonite-Ca