Zeolite was one of the first materials used by NASA to grow plants in space.
Zeolites are naturally occurring minerals most commonly found in specific types of sedimentary rocks in the form of small crystals associated with clays, other silicate and aluminosilicate phases of similar density. Because of zeolite's molecular composition, it has an incredible absorbent/adsorbent ability. As a result, people are constantly developing new applications for the use of zeolite and it is emerging as one of the most useful minerals being excavated today. Zeolites, often referred to as nature's miracle, are naturally occurring microporous, aluminosilicate minerals that are formed where volcanic rocks and ash layers react with alkaline groundwater. Zeolites have also been known to crystallize in shallow marine basins, however like most natural resources found in the earth, the formations occur slowly over thousands of years. Because of how it is formed, naturally occurring zeolites are rarely found in pure form and are often contaminated by varying degrees of minerals such as metals, quartz or clays. Using low-grade zeolites that are contaminated by other minerals can be detrimental to the results, which makes it extremely important to source high-purity zeolite that is suited to the type of application involved. 
Zeolites' porous, honeycomb like molecular structure allows it to accommodate and assist in the exchange of cations such as Na+, K+, Ca2+, MG2+ as well as several others. This unique molecular sieve quality of zeolites allows the positive ions to be readily exchanged and selectively sorted based on the size of the channels of the specific type of zeolite. While natural zeolites were discovered over 250 years ago, people have only recently begun to realize the true potential and capabilities of zeolite. As a result, it has also been dubbed the mineral of the 21st century and new applications are continually being discovered around the world. Zeolite is an inorganic material that originates from volcanic ash that is spewed into the atmosphere during violent eruptions. The volcanic ash plumes often travel thousands of miles before being deposited on the earth's surface. Zeolites are often formed where volcanic rock is immersed in water. This immersion causes a leaching of some of the components. 
First known uses of Zeolite can be traced back the the B.C.E when Roman's employed the mineral in their aqua ducts. Zeolite was not discovered in the USA until the 1950's. In the 1970's it was used in the treating of wastewater ammonia and radioactive material. As the mineral's amazing filtration and absorption ability became more known, people started using it in pools in Europe and the USA. Since the 1980's, Zeolite has been identified for use in many different applications and as such has become a very valuable commodity.
This is a great video on zeolite. Enjoy!