The mineral erionite is considered to be highly carcinogenic and is on the World Health Organisation's list of substances that cause cancer. A few years ago, an entire village in Turkey actually had to be moved, because the substance was very common in the surrounding area and every second inhabitant died of a particular type of cancer caused by breathing in erionite particles. Up to now it has been thought that iron as a constituent element of the mineral erionite is the reason for the carcinogenic effect. However, mineralogists of Friedrich Schiller University Jena (Germany), together with colleagues from the University of Modena (Italy), have discovered that this metal does not even appear in the crystal structure of erionite.