Natural Ca-rich clinoptilolites (heulandites of group 3): new data and review

New min. Si/Al and max. (Ca, Mg)/(K, Na) ratios (3.78 and ∼2, resp.) were obsd. for clinoptilolite [12173-10-3] during the thermal and chem. analyses of 5 sedimentary minerals of the heulandite [1318-63-4] family. A reexamn. of published heulandite analyses demonstrates the existence of natural Ca-rich clinoptilolites.