Zeolites are silicate minerals that have an unusual crystal structure. The structure contains open channels/pores in which cations and water molecules are captured and often loosely bound to the oxygen atoms that compose the channel walls [1,2]. Natural zeolites have two modes of formation: large crystals, often measured in centimeters, found precipitated from hydrothermal fluids that percolate through cavities (vugs) in the tops of lava flows. The other mode of formation is due to explosive volcanic eruptions which produce extensive clouds of ash composed in part of small glass shards. The fine particles drift away from the volcanic eruption centers and on falling into water are altered to crystalline minerals of which zeolites are commonly in high abundance; often reaching 80-90% of the rock. On uplift these sediments are often found as thick deposits that can be mined by open-cast procedures and it is this material that is used as the zeolitic component of the bio-fertilizer.
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