Zeolite has a long history in the water treatment industry dating back to 1925 when Bill Lindsay started a company to build water softeners for homes and businesses. His efforts attracted the attention of Emmitt Culligan about a decade later and a second manufacturer was founded. Both companies exist and thrive to this day, although the zeolite then used has been replaced with a synthetic material called ion exchange resin.
Zeolite is a name applied to a huge number of extremely porous natural minerals mined in a number of worldwide locations. All have in common aluminum and silicates and because of their porosity they all absorb water along with the minerals contained within the water. Unique to the chemistry of each the species of Zeolite, they attract and cling to the positively charged (cationic) minerals in the water with varying degrees of hold (affinity). So a particular species can hold calcium (hardness) and release it when flooded with sodium (salt) thus permitting its use as a water softening agent.
The water softening ability of zeolite has been surpassed by the synthetic ion exchange resins first popularized in Germany in about 1936. The synthetic version is made of roughly 90% styrene and 10% divinylbenzene with about 10 national and international manufacturers maintaining uniform performance and competitive prices. The popularity of zeolite for other than water treatment is so high in the chemical and other industries that they too are being produced synthetically to absorb particular molecular sizes for distillation and waste remediation processes. They are extremely robust and chemically inert compared to the ion exchange resins. Within the water treatment industry one particular species, clinoptilolite, is extremely popular for filtration applications because its irregular shape creates a tortuous path for particulates and its cationic charge attracts extremely fine particulates.