Natrolite, Na2(Si3Al2)O10•2H2O, is a mineral that was named by M. H. Klaproth, 1803, from Greek 'natron', for its sodium content and 'lithos', that is 'stone' . Natrolite is the representative member of a group of zeolites, where zeolites "are hydrated aluminosilicate minerals made from interlinked tetrahedra of alumina (AlO4) and silica (SiO4)" . The origin of the name 'zeolite', as reported by Strekeisen, is very interesting too. It is told that the term zeolite was proposed by A. F. Cronstedt in 1756, since he "observed that upon rapidly heating the material stilbite, it produced large amounts of steam" . Therefore, Cronstedt used Greek 'zeo', to boil, and 'lithos'. Due to their structure, zeolites have channels, through which water and "large ions (such as sodium, potassium, and magnesium)" can "travel into and out of the crystal structure" ; the size of molecules or ions is controlled by size of channels, and zeolites "can act as a chemical sieve. The term molecular sieve refers to a particular property of these materials: the ability to selectively sort molecules based primarily on a size exclusion process. This is due to a very regular pore structure of molecular dimensions" .