Is chabazite a zeolite?
Yes. Chabazite is a zeolite series: the 1997 IMA report accepted three species, -Ca, -Na and -K, and the 2026 IMA list has five. What is and is not chabazite.
Yes. Chabazite is a zeolite, but as a series rather than one species: the 1997 IMA zeolite report accepted three, chabazite-Ca, -Na and -K, and the September 2026 IMA list has five, adding -Sr (1999) and -Mg (2009). All five Handbook sheets print Zeolite group, chabazite series; chabazite-Ca is hardness 4 to 5, density 2.05 to 2.20.
In short
- The definition. Coombs et al., Canadian Mineralogist 35 (1997), the IMA zeolite report, define a zeolite mineral as a crystalline substance with a framework of linked tetrahedra, each of four oxygen atoms around a cation, containing open cavities in the form of channels and cages, usually holding water and exchangeable cations; dehydration occurs mostly below about 400 °C and is largely reversible. Chabazite is accepted under it.
- The three-to-five ledger. In 1997 the report wrote that chabazite is a series consisting of three separate species, with Ca, Na or K most abundant, and that substantial Sr had so far never been reported as the most abundant in natural examples. A script over the September 2026 IMA-CNMNC Master List finds five rows: chabazite-Sr was approved as IMA 1999-040, from Russia, and chabazite-Mg as 2009-060, from Hungary.
- What chabazite is not. The report says willhendersonite has the same framework as chabazite, yet it is a separate IMA species, KCa(Si3Al3)O12·5H2O. Herschelite, a name often applied to tabular, sodium-rich chabazite, should no longer be used as a species name; the report suppresses it in favour of chabazite-Na. The IMA list has no herschelite row, by script.
- When the answer changes. The report suggests sodium-substituted chabazite-Ca for what would in effect be a synthetic chabazite-Na made by cation exchange, and says dehydration, partial hydration and overhydration are not grounds for a separate species. A white rhomb that reads 12.62 g in water for 20.00 g is calcite, not a zeolite; chabazite-Ca reads 10.24 to 10.91 g.
- Which chabazite? That needs an analysis: the suffix is the most abundant extra-framework cation. How the rule plays out on the sheets’ analyses is the suffix decoder on chabazite; the zeolite family as a whole is on which minerals are zeolites.
| Name | IMA formula, September 2026 | IMA status and number | 1997 IMA zeolite report | Density (sheet); 20.00 g in water | Chabazite? |
|---|---|---|---|---|---|
| Chabazite-Ca | Ca2[Al4Si8O24]·13H2O | A, 1997 s.p., Italy | New name for the original and most common species | 2.05 to 2.20; 10.24 to 10.91 g | Yes |
| Chabazite-Na | (Na3K)[Al4Si8O24]·11H2O | A, 1997 s.p., Italy | New name; Na the most abundant single cation | 2.09; 10.43 g | Yes |
| Chabazite-K | (K2NaCa0.5)[Al4Si8O24]·11H2O | A, 1997 s.p., Italy | New name; K the most abundant single cation | 2.05 to 2.20; 10.24 to 10.91 g | Yes |
| Chabazite-Sr | (Sr,Ca)2[Al4Si8O24]·11H2O | A, 1999-040, Russia | Not a species: Sr never yet reported as most abundant in nature | 2.16; 10.74 g | Yes, since 1999 |
| Chabazite-Mg | (Mg0.7K0.5Ca0.5Na0.1)[Al3Si9O24]·10H2O | A, 2009-060, Hungary | Not a species: Mg occasionally significant | 1.98; 9.90 g | Yes, since 2009 |
| Willhendersonite | KCa(Si3Al3)O12·5H2O | A, 1981-030, Italy | Accepted zeolite; same framework as chabazite | 2.10 to 2.18; 10.48 to 10.83 g | No: a separate species |
| Herschelite | No row (script) | - | Discredited; suppressed in favour of chabazite-Na | - | No: an old name |
| Calcite | Ca(CO3) | G, 1836 | Not listed among the zeolites | 2.7102; 12.62 g | No: not a zeolite |
What is a zeolite, and does chabazite qualify?
Chabazite qualifies: the IMA zeolite report accepts the chabazite series, and all five Handbook chabazite sheets print Zeolite group. Coombs et al., Canadian Mineralogist 35 (1997) define a zeolite mineral as a crystalline substance with a structure characterized by a framework of linked tetrahedra, each consisting of four O atoms surrounding a cation. The framework contains open cavities in the form of channels and cages, usually occupied by H2O molecules and extra-framework cations that are commonly exchangeable; in the hydrated phases, dehydration occurs at temperatures mostly below about 400 °C and is largely reversible.
What the sheets add. All five Handbook of Mineralogy chabazite sheets, -Ca, -Na, -K, -Sr and -Mg, print Zeolite group, chabazite series, by script. The chabazite-Ca sheet prints H2O+ 16.28% and H2O− 3.44% in its Ritter Hot Spring analysis and an ideal water content of 22.72%, and places chabazite in volcanic rocks, cavities and joints, and lake-deposit tuff altered from volcanic glass. The tests the site has already used on other minerals are on is prehnite a zeolite and is apophyllite a zeolite.
How many chabazites are there? The three-to-five ledger
The three-to-five ledger: three chabazite species in the 1997 report, five on the 2026 IMA list. The report wrote that zeolites with the chabazite structure have a range of compositions in which any one of Ca, Na or K may be the most abundant extra-framework cation, and that chabazite is a series consisting of three separate species. It added that substantial Sr is in some cases present, but had so far never been reported as the most abundant in natural examples, and that Ca-, Na- and K-dominant species occur in that order of frequency, with Sr and Mg occasionally significant.
What changed. A script over the September 2026 IMA-CNMNC Master List, matching rows that begin Chabazite, returns five: chabazite-Ca, -K and -Na with status A and 1997 s.p., Italy; chabazite-Sr, A, 1999-040, Russia; and chabazite-Mg, A, 2009-060, Hungary. The chabazite-Sr sheet’s analysis, from Suoluaiv Mountain, Lovozero, prints Sr1.08 against Ca0.92: a natural case of what the 1997 report had not yet seen. The rule did not change; the analyses did.
What it means for a label. A label reading chabazite is still correct: the 1997 report says chabazite remains the correct name for a member of the series not specifically identified on compositional grounds. The species names chabazite-Sr and chabazite-Mg date from the IMA approvals 1999-040 and 2009-060. Cataloguing that history is covered in how to label and catalogue a mineral collection.
What is not chabazite, even when it looks or sounds like it
Same framework, different species: willhendersonite. The 1997 report says willhendersonite’s framework is the same as for chabazite, but with much lower Si and with Si,Al fully ordered. It is its own IMA row, KCa(Si3Al3)O12·5H2O, A, 1981-030, Italy, and its sheet describes tabular crystals and trellislike twinned aggregates under 1 mm, hardness about 3, density 2.10 to 2.18. Documented failure: framework is not identity, and at 10.48 to 10.83 g in water for 20.00 g willhendersonite sits inside chabazite-Ca’s 10.24 to 10.91 g.
An old name: herschelite. The report says herschelite has often been applied to chabazite minerals of tabular habit and high Na content, should no longer be used as a species name, and is suppressed in favour of chabazite-Na. The IMA list has no herschelite row, by script. A herschelite label therefore points to chabazite, by that usage a sodium-rich one; only an analysis gives the suffix.
Look-alikes that are not chabazite. Gmelinite is a separate zeolite series on the IMA list (gmelinite-Ca, -K, -Na); its Na sheet allows rhombohedral crystals and a density of 2.02 to 2.17, so the balance does not separate it. calcite is not a zeolite at all, and at 12.62 g in water for 20.00 g it is easy to tell; the bench comparison is on chabazite.
When the answer changes: exchanged, dehydrated and unanalysed chabazite
Exchange in the laboratory does not make a natural species. The 1997 report notes that near-end-member Na, K, Ca and Sr compositions are readily obtained by ion exchange from natural Ca-dominant chabazite at 110 °C, but that this is not the essential criterion for the natural series. It suggests terms such as sodium-substituted chabazite-Ca for what would in effect be a synthetic chabazite-Na prepared by cation exchange.
Water content does not make a new species. The report says dehydration, partial hydration and overhydration are not sufficient grounds for recognising separate zeolite species. A crystal that has lost water on a shelf is still chabazite; this page gives no storage advice.
An unanalysed crystal is chabazite, full stop. The suffix is the most abundant extra-framework cation in atomic proportions; without an analysis the honest name is the series name. The thomsonite question, a different zeolite with its own split, is on is thomsonite a zeolite; the classification questions are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.