The physical and hydrothermal properties of natural zeolite tschernichite, an aluminium-rich analogue of the catalytically important zeolite beta, have been examined. Unlike the compositionally similar zeolite Y, the ammonium form of tschernichite is thermally stable to temperatures as high as 900-degrees-C. Like synthetic beta, this zeolite dealuminates readily with steam treatment (I hr, 100% steam, 550-degrees-C). Crystallinity is decreased by 30% after steaming but tschernichite maintains its large pore adsorption properties. Dealumination produces a framework that is more silica rich than similarly dealuminated zeolite Y and the dealuminated form exhibits properties similar to as-synthesised beta. The Si-29 NMR, framework infrared spectra, and isopropylamine decomposition studies of dealuminated tschernichte further confirm the similarity between this mineral and synthetic beta.