Editing Zeolite (section)

==Natural occurrence==
[[File:Thomsonite-61017.jpg|thumb|left|A form of [[thomsonite]] (one of the rarest zeolites) from India]]

Some of the more common mineral zeolites are [[analcime]], [[chabazite]], [[clinoptilolite]], [[heulandite]], [[natrolite]], [[phillipsite]], and [[stilbite]]. An example of the mineral formula of a zeolite is: {{Chem2|Na2Al2Si3O10}}·2H<sub>2</sub>O, the formula for [[natrolite]].

Natural zeolites form where [[volcanic]] rocks and [[volcanic ash|ash]] layers react with [[alkaline]] groundwater. Zeolites also crystallize in post-depositional environments over periods ranging from thousands to millions of years in shallow marine basins. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, metals, [[quartz]], or other zeolites. For this reason, naturally occurring zeolites are excluded from many important commercial applications where uniformity and purity are essential.{{Citation needed|date=June 2021|reason=No citation for anything in paragraph}}

Zeolites transform to other minerals under [[weathering]], [[hydrothermal alteration]] or [[metamorphism|metamorphic]] conditions. Some examples:<ref name="Tschernich-1992">{{Cite book|url=https://www.mindat.org/article.php/507/Mindat%27s+15th+Birthday+and+a+present+for+everyone|title=Zeolites of the World|vauthors=Tschernich RW|publisher=Geoscience Press|year=1992|isbn=9780945005070|url-access=registration}}</ref>
* The sequence of [[silica]]-rich [[volcanic rock]]s commonly progresses from:
** [[Clay]] → quartz → [[mordenite]]–[[heulandite]] → [[epistilbite]] → [[stilbite]] → [[thomsonite]] → [[mesolite]] → [[scolecite]] → [[chabazite]] → [[calcite]].{{citation needed|reason= Clay becomes quartz???|date=October 2018}}
* The sequence of silica-poor volcanic rocks commonly progresses from:
** [[Cowlesite]] → [[levyne]] → [[offretite]] → [[analcime]] → [[thomsonite]] → [[mesolite]] → [[scolecite]] → [[chabazite]] → [[calcite]].

=== Gemstones ===
[[File:Thomsonite-Ca-55547.jpg|thumb|upright|Polished thomsonite]]
[[Thomsonite]]s, one of the rarer zeolite minerals, have been collected as [[gemstone]]s from a series of [[lava]] flows along [[Lake Superior]] in [[Minnesota]] and, to a lesser degree, in [[Michigan]]. Thomsonite nodules from these areas have [[erosion|eroded]] from [[basalt]] lava flows and are collected on beaches and by scuba divers in Lake Superior.

These thomsonite nodules have concentric rings in combinations of colors: black, white, orange, pink, purple, red, and many shades of green. Some nodules have copper inclusions and rarely will be found with [[copper]] "eyes". When polished by a [[lapidary]], the thomsonites sometimes displays a "cat's eye" effect ([[chatoyancy]]).<ref name="Dietrich">{{cite web|url=http://stoneplus.cst.cmich.edu/thomsonite.htm|title=Thomsonite|author=Dietrich RV|date=2005|website=GemRocks|access-date=2 Oct 2013}}</ref>