Mordenite
Mordenite, (Na2,Ca,K2)4(Al8Si40)O96·28H2O: a fibrous to prismatic orthorhombic zeolite, hardness 3 to 4, density 2.12 to 2.15, named for Morden, Nova Scotia.
Mordenite is a zeolite, (Na2,Ca,K2)4(Al8Si40)O96·28H2O on the IMA list (A, 1997 s.p., Canada), and a single species with no cation suffix. Its Handbook sheet gives orthorhombic prisms and acicular to fine fibrous crystals to 2.5 cm, hardness 3 to 4, density 2.12 to 2.15 and perfect {100} cleavage. It is named for Morden, Nova Scotia.
In short
- Formula and status. The September 2026 IMA-CNMNC Master List gives (Na2,Ca,K2)4(Al8Si40)O96·28H2O, status A, 1997 s.p., Canada. The Handbook of Mineralogy sheet writes it on a quarter of the oxygens, (Ca,Na2,K2)Al2Si10O24·7H2O, in the zeolite group. Worked: Si:Al is 5 to 1, and the calcium form is 67.89% SiO2 and 14.25% water by mass.
- One name, no suffix. A script finds one IMA row for mordenite, where gmelinite, chabazite and phillipsite each split by dominant cation. The IMA zeolite report (Coombs et al. 1997) gives Na/(Na+Ca) typically 0.50 to 0.81 and notes reports of K-dominant material, potentially justifying a mordenite series with Na- and K-dominant species; the 2026 list has not split it.
- The Coyote check. Recast on 24 oxygens, the sheet’s two analyses both put sodium first by atoms: Challis, Idaho, Na 1.11 to Ca 0.48, as printed; Coyote, Utah, Na 0.76 to Ca 0.62. The sheet prints Coyote as Ca1.24, which is the charge 0.62 calcium atoms carry, and its Σ = 2.02 is a charge sum, matching Al 2.01. Na/(Na+Ca) is 0.698 and 0.552, inside the report’s range; read as printed, Coyote would give 0.380.
- Documented failure: the water does not reproduce. Challis is printed with 5.86 H2O; the recast gives 4.55 from H2O+ alone and 6.86 counting H2O− as well, exactly 1.00 above the printed figure. Coyote’s printed 6.94 is close to its 6.90 from both waters. On the sheet’s smallest cell the ideal calcium formula gives 2.128 and the sodium form 2.142, against the printed D(calc.) 2.125.
- Fibrous, and where. The sheet’s habit runs from striated prisms to acicular and fine fibrous crystals in radiating groups or cottony aggregates, silky if fibrous. Distribution: Morden and the Bay of Fundy, Nova Scotia; Challis, Idaho; Goble and Cape Lookout, Oregon; Table Mountain, Colorado; the Berufjord area, Iceland; the Poona district, India.
| Analysis or formula | Na | Ca | K | Al : Si | Na/(Na+Ca) | H2O per 24 O | Reproduces the sheet? |
|---|---|---|---|---|---|---|---|
| Challis, Idaho, recast (average of four analyses) | 1.11 | 0.48 | 0.09 | 2.15 : 9.80 | 0.698 | 4.55 (H2O+); 6.86 (both) | Cations yes; printed 5.86 H2O no |
| Challis, as printed | 1.11 | 0.48 | 0.10 | 2.16 : 9.80 | 0.698 | 5.86 | — |
| Coyote, Utah, recast | 0.76 | 0.62 | 0.02 | 2.01 : 9.99 | 0.552 | 4.36 (H2O+); 6.90 (both) | Na and water yes; Ca is half the printed figure |
| Coyote, as printed | 0.76 | 1.24 | 0.02 | 2.02 : 10.04 | 0.380 | 6.94 | Ca1.24 is 0.62 × 2: a charge, not an atom count |
| Ideal calcium form, CaAl2Si10O24·7H2O | 0 | 1 | 0 | 2 : 10 | 0 | 7 (14.25% by mass) | D 2.128 on the cell; printed D(calc.) 2.125 |
| Ideal sodium form, Na2Al2Si10O24·7H2O | 2 | 0 | 0 | 2 : 10 | 1 | 7 (14.16%) | D 2.142 on the same cell |
| Sheet, measured | — | — | — | — | — | — | D 2.12 to 2.15; 10.57 to 10.70 g in water |
What is mordenite? One zeolite species, no suffix
The formula. The September 2026 IMA list gives (Na2,Ca,K2)4(Al8Si40)O96·28H2O, status A (approved), 1997 s.p. (special procedure, the IMA zeolite subcommittee report), with Canada as the country of first description; its first reference is the Journal of the Chemical Society 17 (1864). The Handbook of Mineralogy mordenite sheet writes (Ca,Na2,K2)Al2Si10O24·7H2O, the same formula divided by four, and Mineral Group: zeolite group. The IMA zeolite report (Coombs et al. 1997) gives the cell content (Na2,Ca,K2)4[Al8Si40O96]·28H2O, Z = 1, the framework type code MOR, and How (1864) as the original reference; it says the structure was determined by Meier (1961) and that Si,Al disorder in the framework is extensive but not complete.
Why there is no mordenite-Na. The report names members of a zeolite series by the most abundant extra-framework cation, which is why chabazite has five IMA rows and phillipsite three. Mordenite is treated as one species with a variable cation content; the report notes K-dominant reports that would potentially justify a series, and the 2026 list still has one row. Older names the report equates with mordenite include ptilolite, flokite, arduinite, steeleite and pseudonatrolite; the sheet’s own references cite “Ptilolite [mordenite] from Utah” (Schaller 1932). Other zeolites are on which minerals are zeolites and in the species index.
Mordenite crystals: fibrous, cottony or porcelaneous
What the sheet describes. Prismatic crystals, striated parallel to their length; acicular to fine fibrous, to 2.5 cm; in radiating groups or cottony aggregates; also compact and porcelaneous. Cleavage is perfect on {100} and distinct on {010}, the fracture uneven, the tenacity brittle, hardness 3 to 4. Colourless, white, yellowish or pinkish, with a vitreous lustre that is pearly on {010} and silky if fibrous. Reading a cleavage on a fibre bundle is hard; the general method is on cleavage or fracture: how to tell.
Fibres, in one line. Questions about handling fibrous zeolite material are routed to toxic minerals in a collection; nothing on this page is health or safety advice. White fibrous sprays from basalt cavities include several species, and is okenite a zeolite compares okenite with natrolite, mesolite, scolecite and thomsonite; mordenite’s own numbers, density 2.12 to 2.15 and indices 1.472 to 1.487, are on this page.
The Coyote check: atoms or charges
Method. Each oxide of the sheet’s two analyses is divided by its molar mass and scaled so the anhydrous oxygens total 24. Challis, Idaho (average of four analyses: SiO2 66.06, Al2O3 12.32, MgO 0.36, CaO 3.02, Na2O 3.86, K2O 0.50, H2O+ 9.19, H2O− 4.68, total 99.99) gives Na 1.11, Ca 0.48, K 0.09, Mg 0.08, Al 2.15, Si 9.80, which reproduces the printed (Na1.11Ca0.48K0.10Mg0.08)Σ=1.77Al2.16Si9.80O24 to within 0.01. Coyote, Garfield Co., Utah (SiO2 67.35, Al2O3 11.49, CaO 3.87, Na2O 2.63, K2O 0.11, H2O+ 8.82, H2O− 5.13, total 99.40) gives Na 0.76, Ca 0.62, K 0.02, Al 2.01, Si 9.99, against the printed Al 2.02 and Si 10.04.
Result. The sheet prints Coyote as (Ca1.24Na0.76K0.02)Σ=2.02. Its calcium is twice the recast 0.62, and its sum, 2.02, equals the positive charge the cations carry (2 × 0.62 + 0.76 + 0.02) and the aluminium they balance, not the 1.40 atoms present. Read as atoms, as the report’s naming rule counts them, both analyses are sodium-led and both sit inside its typical Na/(Na+Ca) of 0.50 to 0.81. Because mordenite has no suffix the name does not change; the check matters when an analysis is quoted on a label. This page reports the arithmetic and does not correct the sheet.
Mordenite structure and XRD: what the sources give
Powder pattern. The sheet’s X-ray powder pattern is from Aros, Isle of Mull, Scotland: 3.483 (10), 3.222 (10), 9.10 (9), 6.61 (9), 3.999 (9), 3.393 (9), 4.525 (8): spacings in Å with relative intensities in brackets. The cell is orthorhombic, space group Cmc21 or Cmcm, a 18.052 to 18.168, b 20.404 to 20.527, c 7.501 to 7.537 Å, Z = [4]; the 1997 report gives Cmcm and the same ranges (Passaglia 1975). The framework code MOR is the report’s; the IZA structure database did not return a page to this site’s fetch, so no channel dimensions are quoted.
Density from the cell. Worked as Z × formula mass × 1.66054 ÷ cell volume, the ideal calcium form on the smallest cell gives 2.128 and on the largest 2.091; the sodium form 2.142 and 2.105; the potassium form 2.219 and 2.181. The printed D(calc.) 2.125 sits by the calcium form on the smallest cell, and the measured 2.12 to 2.15 overlaps both the calcium and the sodium values. A balance does not read the cation; the method is on how to measure specific gravity at home.
Where mordenite is found
Occurrence. In veins and amygdules in various igneous rocks; a hydration product of volcanic glasses; an authigenic mineral in sediments. Associates: zeolites, calcite, kaolinite, glauconite. The Distribution field says many localities give abundant, well-crystallised material and names Morden and the Bay of Fundy, Nova Scotia; near Stevenson, Washington; Challis, Idaho; Crooked Creek, Goble and Cape Lookout, Oregon; Table Mountain and Wolf Creek Pass, Colorado; Crestmore, California; Union Pass, Arizona; San Piero in Campo, Elba; the Berufjord area, Iceland; and Cinchwad and elsewhere in the Poona district, India. The sheet marks no type locality.
Neighbours. Other zeolites with pages here include laumontite, phillipsite and gmelinite; thomsonite’s case is on is thomsonite a zeolite. More species are in the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.