A. Types of occurrences
The mineral combinations in which zeolites are found are widespread, and recognition of a special mineral facies , the zeolite facies , has been proposed (7). Until about twenty years ago , zeolite minerals were considered as typically occurring in cavities of basaltic and volcanic rocks. Dating from the discovery of stilbite by Cronstedt in 1756 , numerous publications describe the occurrence and mineralogy of zeolite mineral assemblages in basaltic igneous rocks. During the last 50 years, a number of brief descriptions of zeolite minerals found in sediments and as alteration products of volcanic ash and other pyroclastic materials have appeared. Ross (8) speculated in 1928 that analcime in the Wickieup , Arizona lake sediments was formed by the action of saline lake water on volcanic ash. More recently , the use of x-ray diffraction for the examination o0f very fine-grained submicroscopic part-isles that occur in sediments has resulted in the identification of several zeolite minerals which formed during diagenesis of volcanic ash particles in alkaline environments (5). The mineral phillipsite was found in the walls of Roman baths by Daubree at Plombieres, France, in 1879 (3). Drill cores from wells in Wairakei, New Zealand revealed an extensive zone of zeolite formation (9).