Machine learning study of the heulandite family of zeolites

Heulandite and clinoptilolite form the most abundant family of natural zeolite crystals. The topology of both of them is characterized by the framework type HEU. Despite many studies on these crystals, the mineral assignment to a zeolite as heulandite or clinoptilolite is still controversial and unresolved today. Based on a machine learning clustering analysis of crystallographic data of zeolite crystals, we show that zeolites belonging to the HEU framework type are divided into three groups of minerals instead of two. Two of the groups, HEU-h and HEU-c, contain crystals with names heulandite and clinoptilolite, respectively. The third newly proposed group HEU-m is composed of mixed zeolites named under both traditional names. The grouping is based on the EM algorithm and a set of descriptors built from data collected in the NIST/FIZ Inorganic Crystal Structure Database. Verification of the division of the HEU family into three groups is provided based on a battery of machine learning tests.