Last updated: March 5, 2018. Heat a glass of water and you'll see steam rise off it sooner or later as it comes to the boil. You certainly don't expect the same thing to happen if you heat a rock—unless it's a special kind of rock called a zeolite, which traps water inside it. Back In 1756, Swedish geologist Axel Cronstedt (1722–1765)—best known as the discoverer of —coined the name 'zeolite' because it literally means 'boiling stone'; today, the term refers to over 200 different minerals that have all kinds of interesting uses, from water softeners and cat litter to animal food and industrial catalysts. What are zeolites and how do they work? Let's take a closer look!
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Pure Liquid Zeolite Frequently Asked Questions page answers all your questions about Zeolite. (not into the molecular cages described above). This explains why zeolites seem to block the development of many viral infections, including herpes virus 1, coxsackie virus B-5, echovirus 7, and adenovirus 5. Over forty anecdotal cases of herpes zoster have reportedly been healed, with sufferers.
Photo: The power of nothingness: in zeolite crystals, like the one in this illustration, the pores in between the aluminum, silicon, and oxygen atoms are as important as the crystal structure itself. By courtesy of NASA Marshall Space Flight Center (NASA-MSFC). What are zeolites? Chart: Where do natural zeolites come from? Estimated world mine production for 2017.
China remains the leading producer, accounting for about a third of all natural zeolites (300,000 tons), but nothing like the 2 million tons that it had previously claimed to produce. Source:, January 2018. According to the USGS, total world reserves of zeolites are unknown 'but are estimated to be large.' Zeolites are hydrated aluminosilicate minerals made from interlinked tetrahedra of alumina (AlO 4) and silica (SiO 4). In simpler words, they're solids with a relatively open, three-dimensional crystal structure built from the elements, oxygen, and silicon, with alkali or alkaline-Earth metals (such as sodium, potassium, and magnesium) plus molecules trapped in the gaps between them. Zeolites form with many different crystalline structures, which have large open pores (sometimes referred to as cavities) in a very regular arrangement and roughly the same size as small molecules. There are about 40 naturally occurring zeolites, forming in both volcanic and sedimentary rocks; according to the US Geological Survey, the most commonly mined forms include,, and.
Dozens more artificial, synthetic zeolites (around 150) have been designed for specific purposes, the best known of which are zeolite A (commonly used as a laundry detergent), zeolites X and Y (two different types of, used for catalytic cracking), and the petroleum catalyst (a branded name for pentasil-zeolite). What special properties do zeolites have? Zeolites are very stable solids that resist the kinds of environmental conditions that challenge many other materials. High temperatures don't bother them because they have relatively high melting points (over 1000°C), and they don't burn. They also resist high pressures, don't disssolve in water or other inorganic solvents, and don't oxidize in the air. They're not believed to cause health problems through, for example, skin contact or inhalation, though in fibrous form, they may have. Since they're unreactive and based on naturally occurring minerals, they're not believed to have any harmful environmental impacts.
Although zeolites might sound incredibly boring, their stable and unreactive nature isn't what makes them useful. Animation (above): Ion exchange in zeolites: the zeolite 'cage' (gray) traps incoming ions (red and orange) and releases others (yellow) in their place. The most interesting thing about zeolites is their open, cage-like, 'framework' structure and the way it can trap other molecules inside it.
This is how water molecules and alkali or alkaline-Earth metal (positively charged atoms with too few electrons, sometimes called cations) become a part of zeolite crystals—although they don't necessarily remain there permanently. Zeolites can exchange other positively charged ions for the metal ions originally trapped inside them (technically this is known as cation exchange) and, as Cronstedt found over 250 years ago, they can gain or lose their water molecules very easily too (this is called reversible dehydration). Zeolites have regular openings in them of fixed size, which let small molecules pass straight through but trap larger ones; that's why they're sometimes referred to as molecular sieves. Unlike natural zeolites, which occur in random forms and mixed sizes, synthetic zeolites are manufactured in very precise and uniform sizes (typically from about 1μm to 1mm) to suit a particular application; in other words, they're made a certain size to trap molecules of a certain (smaller) size inside them.