Chabazite
Chabazite is a zeolite series of five IMA species, -Ca, -K, -Mg, -Na and -Sr: rhombohedral, hardness 4 to 5, density 2.05 to 2.20. How the suffix is decided.
Chabazite is a zeolite series, not a single species: the September 2026 IMA list has five rows, chabazite-Ca, -K, -Mg, -Na and -Sr, and no plain chabazite. The chabazite-Ca sheet gives rhombohedral, nearly equant crystals to 4.5 cm, hardness 4 to 5, density 2.05 to 2.20. The suffix names the most abundant extra-framework cation, which takes an analysis.
In short
- Five species, one name. A script over the September 2026 IMA-CNMNC Master List finds 5 rows beginning Chabazite: -Ca, -K and -Na (A, 1997 s.p., Italy), -Sr (A, 1999-040, Russia) and -Mg (A, 2009-060, Hungary). There is no row for plain chabazite. Each Handbook of Mineralogy sheet says plain chabazite is the correct name for a member of the series not specifically identified on compositional grounds.
- The suffix decoder. Coombs et al., Canadian Mineralogist 35 (1997) name a zeolite species by the extra-framework cation most abundant in atomic proportions. Read off the seven analyses on the five sheets, the winner holds 84.7% of those cations in the Ritter Hot Spring chabazite-Ca but only 36.0% in the chabazite-Sr and 37.6% in the chabazite-Mg analysed, where it leads by 0.16 and 0.15 atoms. Most does not mean most of them.
- The rhomb check against calcite. Chabazite’s nearly cubic rhombs are the calcite look-alike. A 20.00 g piece reads 9.90 to 10.91 g in water across the five sheets; calcite at 2.7102 reads 12.62 g, 1.71 g heavier than the heaviest chabazite. Hardness 4 to 5 against 3; cleavage distinct against perfect.
- Documented failures. Gmelinite-Na, which its sheet says may be rhombohedral, reads 10.10 to 10.78 g, inside chabazite’s window, at hardness 4.5. On a refractometer calcite’s lower index, 1.486, falls inside chabazite-Ca’s 1.478 to 1.493; calcite’s other reading, 1.658, does not. And no bench test reads the suffix.
- Is chabazite a zeolite? Yes: all five sheets print Zeolite group, chabazite series. How the 1997 report’s three species became five, and what shares chabazite’s framework without being chabazite, is on is chabazite a zeolite.
| Sheet and analysis | Extra-framework cations as printed | Most abundant | Its share of those cations | Runner-up; margin | IMA row |
|---|---|---|---|---|---|
| Chabazite-Ca: Ritter Hot Spring, Grant Co., Oregon | Ca1.88 K0.20 Na0.10 Mg0.04 | Ca | 84.7% | K 0.20; 1.68 | A, 1997 s.p., Italy |
| Chabazite-Na: Aci Trezza, Sicily [TL] | Na3.11 K1.05 Ca0.19 Mg0.06 | Na | 70.5% | K 1.05; 2.06 | A, 1997 s.p., Italy |
| Chabazite-Na: Foveaux Formation, New Zealand | Na2.51 K1.13 Ca0.17 Mg0.02 | Na | 65.5% | K 1.13; 1.38 | As above |
| Chabazite-K: Foveaux Formation, analysis (1) | K1.72 Na1.18 Mg0.23 Ca0.08 | K | 53.6% | Na 1.18; 0.54 | A, 1997 s.p., Italy |
| Chabazite-K: Foveaux Formation, analysis (2) | K1.92 Na1.67 Ca0.18 Mg0.17 | K | 48.7% | Na 1.67; 0.25 | As above |
| Chabazite-Sr: Suoluaiv Mountain, Lovozero, Russia | Sr1.08 Ca0.92 K0.68 Na0.30 Ba0.02 | Sr | 36.0% | Ca 0.92; 0.16 | A, 1999-040, Russia |
| Chabazite-Mg: Prága Hill, Hungary | Mg0.67 K0.52 Ca0.48 Na0.08 Sr0.03 | Mg | 37.6% | K 0.52; 0.15 | A, 2009-060, Hungary |
What is chabazite? A series name with five species
Chabazite is the name of a zeolite series; the species are chabazite-Ca, chabazite-K, chabazite-Mg, chabazite-Na and chabazite-Sr. A script over the September 2026 IMA-CNMNC Master List, matching rows that begin Chabazite, finds those five and no other. The IMA formulas are Ca2[Al4Si8O24]·13H2O, (K2NaCa0.5)[Al4Si8O24]·11H2O, (Mg0.7K0.5Ca0.5Na0.1)[Al3Si9O24]·10H2O, (Na3K)[Al4Si8O24]·11H2O and (Sr,Ca)2[Al4Si8O24]·11H2O. Four share a framework of 4 aluminium and 8 silicon; chabazite-Mg has 3 and 9.
What a plain label means. Each of the five Handbook of Mineralogy sheets says plain chabazite is the correct name for a member of the series that is not specifically identified on compositional grounds. An old label reading chabazite is therefore correct as far as it goes; it records the series, not the species. Coombs et al., Canadian Mineralogist 35 (1997) add that informal terms such as calcium chabazite should not appear in print as mineral names. Cataloguing a series name honestly is covered in how to label and catalogue a mineral collection.
What the sheets record. The chabazite-Ca sheet: pseudohexagonal, point group −3 2/m; crystals rhombohedral, nearly equant, to 4.5 cm; tabular, complex to rounded twins; anhedral, granular or massive; interpenetrant twins, simple and repeated, common. Cleavage distinct, fracture uneven, brittle. Hardness 4 to 5; density 2.05 to 2.20 measured. White, yellow, pink, red or colorless, streak white, vitreous. Optically biaxial (+) or (−) or uniaxial, commonly with birefringent panelling in six sections. The name is from the Greek chabazios, an ancient name of a stone.
Which chabazite is it? The suffix decoder
The suffix decoder: take the analysis, count the extra-framework cations, and the largest count names the species, even when it is well short of half. That is Rule 5 of Coombs et al., Canadian Mineralogist 35 (1997): the suffix is the chemical symbol for the extra-framework element most abundant in atomic proportions, for example chabazite-Ca. The sheets repeat it: a suffix indicates the most abundant extra-framework cation.
Worked on the sheets’ own analyses. The Ritter Hot Spring, Oregon chabazite-Ca prints Ca1.88 K0.20 Na0.10 Mg0.04: calcium is 84.7% of the 2.22 cations. The type chabazite-Na from Aci Trezza, Sicily, Na3.11 K1.05 Ca0.19 Mg0.06, is 70.5% sodium. The chabazite-K sheet’s second Foveaux Formation analysis, K1.92 Na1.67 Ca0.18 Mg0.17, gives potassium 48.7%: under half, and still chabazite-K. Recalculated from the Ritter Hot Spring oxides on 12 silicon plus aluminium, the script gives Ca 1.89, K 0.20, Na 0.10 and Mg 0.05, within 0.01 of the printed figures.
Where the decoder is thinnest. The chabazite-Sr sheet’s analysis from Suoluaiv Mountain, Lovozero, Russia, prints Sr1.08 Ca0.92 K0.68 Na0.30 Ba0.02: strontium leads calcium by 0.16 atoms and is 36.0% of the cations. The chabazite-Mg from Prága Hill, Hungary, prints Mg0.67 K0.52 Ca0.48 Na0.08 Sr0.03: magnesium leads by 0.15 and is 37.6%. The 1997 report notes Ca-, Na- and K-dominant species occur in that order of frequency. None of this is visible in the hand; a suffix on a label is only as good as the analysis behind it.
Chabazite or calcite? The rhomb check
The rhomb check: a nearly cubic white rhomb that reads under 11 g in water for 20.00 g is not calcite. Across the five chabazite sheets, densities of 1.98 to 2.20 give 9.90 to 10.91 g, worked as 20 − 20/D. The calcite sheet’s 2.7102 gives 12.62 g, 1.71 g heavier than the heaviest chabazite. The method is on how to measure specific gravity at home. Hardness agrees: 4 to 5 for chabazite-Ca against calcite’s 3. Calcite’s {10-11} cleavage is perfect; chabazite’s is distinct.
Where the rhomb check fails, documented. The Gmelinite-Na sheet describes euhedral crystals, pyramidal, tabular or rhombohedral, hardness 4.5, density 2.02 to 2.17: 10.10 to 10.78 g in water, inside chabazite’s window. Its sheet places it in the zeolite group too, so the balance says zeolite, not which one. On a refractometer, calcite’s lower index, ε = 1.486, falls inside chabazite-Ca’s α = 1.478 to 1.487 and γ = 1.480 to 1.493; only calcite’s other reading, ω = 1.658, separates them.
Under a UV lamp. The calcite sheet says it may fluoresce in several colours. None of the five chabazite sheets prints any fluorescence, by a search that also matches the stray glyph pdftotext leaves for the fl ligature, checked against the hemimorphite and willemite sheets, which print it. Absence on a sheet is not a test result, and this page gives no colour; the background is on fluorescent minerals explained.
Where chabazite is found
The chabazite-Ca sheet’s Occurrence field: in volcanic rocks such as basalts and andesite; rarer in limestones and schists; hydrothermally deposited in cavities and joints in ore veins; in tuff in lake deposits, altered from volcanic glass. Associates are zeolites, nepheline, melilite, olivine, pyroxenes, amphiboles, axinite, epidote, calcite, tridymite and dolomite.
Its Distribution field calls chabazite-Ca a common zeolite and names fine crystals from Idar-Oberstein, Rhineland-Palatinate, Germany; Řepčice (Rübendörfel), near Ústí nad Lábem, Czech Republic; several localities in Co. Antrim, Ireland; Kilmalcolm, Renfrewshire, Scotland; Haeddin on Eysturoy, Dalsnipa on Sandoy and Skutin on Nolsoy, Faeroe Islands; large crystals at Breidhdalsheidhi, Iceland; Paterson and Bergen Hill, New Jersey; Table Mountain, Colorado; Goble and Springfield, Oregon; the Bay of Fundy district, Nova Scotia; Table Mountain, Rosarito Beach, Baja California; the Khandivali quarry near Bombay, India; and Richmond, Collingwood and Fairy Mount, Australia.
The other four. The chabazite-Na sheet marks Aci Trezza, Sicily, as type locality [TL]; the chabazite-K sheet, Tufo Ercolano, Naples, Italy [TL]; both add analysed material from the Foveaux Formation, Bluff Peninsula, New Zealand. Chabazite-Sr is known on its sheet from Suoluaiv Mountain, Lovozero massif, Kola Peninsula, in a K-feldspar and aegirine pegmatite veinlet. Chabazite-Mg is from Prága Hill, Balaton Highland, Hungary, and the Ugione Valley, Livorno, Italy, as rhombohedra to 0.4 mm. The type-locality idea is explained in what a type locality is.
Chabazite among the zeolites on this site
Chabazite sits with the cavity zeolites. The chabazite-Ca sheet lists zeolites first among its associates, and it shares basalt cavities with stilbite, heulandite, analcime and the fibrous natrolite group, compared on natrolite vs scolecite. The definition of a zeolite, and why prehnite is not one, is on which minerals are zeolites and is prehnite a zeolite.
Two neighbours to name. Coombs et al., Canadian Mineralogist 35 (1997) say willhendersonite has the same framework as chabazite; its IMA row is KCa(Si3Al3)O12·5H2O, A, 1981-030, Italy. Thomsonite, another basalt zeolite with a very different habit, is on is thomsonite a zeolite. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.