This report embodies recommendations on zeolite nomenclature approved by the International Mineralogical Association Commission on New Minerals and Mineral Names. In a working definition of a zeolite mineral used for this review, interrupted tetrahedral framework structures are accepted where other zeolitic properties prevail, and complete substitution by elements other than Si and Al is allowed. Separate species are recognized in topologically distinctive compositional series in which different extra-framework cations are the most abundant in atomic proportions. To name these, the appropriate chemical symbol is attached by a hyphen to the series name as a suffix except for the names harmotome. pollucite and wairakite in the phillipsite and analcime series. Differences in space-group symmetry and in order-disorder relationships in zeolites having the same topologically distinctive framework do not in general provide adequate grounds for recognition of separate species. Zeolite species are not to be distinguished solely on Si:Al ratio except for heulandite (Si:Al or =4.0). Dehydration, partial hydration, and over-hydration are not sufficient grounds for the recognition of separate species of zeolites. Use of the term "ideal formula" should be avoided in referring to a simplified or averaged formula of a zeolite. Newly recognized species in compositional series are as follows: brewsterite-Sr, -Ba: chabazite-Ca, -Na, -K; clinoptilolite-K, -Na, -Ca; dachiardite-Ca, -Na; erionite-Na, -K, -Ca: faujasite-Na, -Ca, -Mg; ferrierite-Mg, -K, -Na; gmelinite-Na, -Ca, -K; heulandite-Ca, -Na, -K, -Sr; levyne-Ca, -Na; paulingite-K, -Ca; phillipsite-Na, -Ca, -K; stilbite-Ca, -Na. Key references, type locality, origin of name, chemical data, IZA structure-type symbols, space-group symmetry, unit-cell dimensions, and comments on structure are listed for 13 compositional series. 82 accepted zeolite mineral species, and three of doubtful status. Herschelite, leonhardite, svetlozarite, and wellsite are discredited as mineral species names. Obsolete and discredited names are listed.

/pdf/recommended-nomenclature-for-zeolite-minerals-report-of-the-2rzaitmfow.pdf

Recommended nomenclature for zeolite minerals: report of the subcommittee on zeolites of the International Mineralogical Association, Commission on New Minerals and Mineral Names

### Definition of zeolite

This chapter discusses the crystal chemistry, emphasizing observed chemical variations, for those zeolites that completely fulfill the requirements of Smith (1963) for a zeolite. These requirements include: (a) a three-dimensional framework of tetrahedra occupied more than 50% by Si and Al; (b) an “open” structure with a framework density (i.e. number of tetrahedral atoms per 1000 A3) lower than 20 (Brunner and Meier 1989) and hence enclosing cavities connected by windows larger than regular six-membered rings; and (c) an extraframework content represented by cations and water molecules. Thus, this chapter will not deal with those phases which are commonly classified as feldspathoids (leucite, pollucite) and those that can be classified as beryllo-phosphates (pahasapaite, weinebeneite), beryllo-silicates (chiavennite, hsianghualite), or zinc-silicates (gaultite). The requirements of Smith (1963) account for the characteristic properties of zeolites (molecular sieve, reversible dehydration, cation exchange), and although for some zeolite species, cation exchange is incomplete or is not yet reported, the presence of large windows (requisite b) reasonably assures its feasibility. Using the above criteria, all minerals known to date which can be classified as zeolites are listed in Table 1⇓.

View this table:

 Table 1. 
Schematic chemical formulae of natural zeolites. STC = Structure Type Code; Ra = Average Si/(Si+Al+Be); Rr = Range of Si/(Si+Al+Be); DEC = Dominant Extraframework Cations; SEC = Subordinate Extraframework Cations. Italic: Be-bearing species. Underlined: species with an “interrupted framework”



In the general formula MxDy[Alx+2ySin-(x+2y)O2n]· m H2O, where M are monovalent and D are divalent cations, it is possible to distinguish two parts, which although very different, are mutually dependent and form a homogeneous complex endowed with exclusive chemico-physical properties. The portion in square brackets represents the tetrahedral framework and is characterized by an overall negative charge which increases as …

The Crystal Chemistry of Zeolites

Low-grade alteration of basaltic lavas at Teigarhorn, eastern Iceland, resulted in three distinct stages of mineral paragenesis that correlate to events in the burial and intrusive history of Icelandic crust. Metasomatism and brittle deformation during the paragenetic stages dramatically affected the paleo- hydrology of the lavas and formed temporally distinct mineral assemblages. The lavas initially contained up to 22 percent total porosity concentrated near the tops and bottoms of individual lava flows. Celadonite and silica (Stage I) precipi- tated along the walls of primary pores prior to deep burial of the lavas and occluded 8 percent of the initial porosity. During burial (Stage II), hydrolysis of olivine and basaltic glass led to the formation of mixed-layer chlorite/smectite clays in the matrix of the lavas and as rims filling 40 percent of the volume of primary pores. Chlorite contents in Stage II mixed-layer clay rims increased from 20 to 80 percent during the infilling of individual vesicles, reflecting increas- ing temperatures with time as the lavas were buried. The end of Stage II occurred after burial and is represented by filling of 40 percent of total primary porosity by zeolites (scolecite or heulandite stilbite mordenite epistilbite) and re- placement of plagioclase by zeolites and albite. The Stage II zeolite assemblages are indicative of two regional metamorphic mineral zones in eastern Iceland, the mesolite scolecite and heulandite stilbite zones. The presence of the bound- ary between the mesolite scolecite and heulandite stilbite zones indicates that the maximum temperature during burial metamorphism was 90° 10°C. Localized areas of intense hydrothermal alteration associated with intrusion of basaltic dikes (Stage III) overprint Stages I and II. Extensive fracturing and hydrothermal brecciation during Stage III added 3 to 11 percent total porosity in which mm- to cm-scale museum-grade crystals of quartz, calcite (Iceland spar), stilbite, scolecite, heulandite, and laumontite precipitated. Estimates of the tem- perature during Stage III (based on fluid inclusion homogenization temperatures in calcite, chlorite geothermometry, and the zeolite assemblage) range from 120° to 180°C. Although the thermobarometric conditions during Stages II and III led to similar mineral assemblages, careful attention to textural and geologic rela- tions permits seemingly complex, multi-stage parageneses in metabasalts to be interpreted in a petrotectonic context.

http://www.geology.yale.edu/~ajs/1999/06.1999.02Neuhoff.pdf

Porosity evolution and mineral paragenesis during low-grade metamorphism of basaltic lavas at Teigarhorn, eastern Iceland

The crystal structure refinement of a natural mordenite

Location of Brønsted sites in mordenite

Mordenite is a zeolite whose approximate composition is (Na2, K2,Ca)4[Al8Si40O96] 28 H2O. Unit cell dimensions, determined by X-ray powder diffractometry for 35 natural samples, fell within the following ranges: a=18.052–18.168, b=20.404–20.527, c=7.501–7.537 A. The indexed powder pattern of a typical sample is reported. Complete wet chemical analyses of 12 samples, partial analyses of three others, and 6 analyses from the literature reveal that mordenites vary only slightly in chemical composition. Si occupies 80 to 85% of the tetrahedra, and the exchangeable cations are mainly Na and Ca, with minor K. The lattice constant b is negatively correlated to the ratio Si/(Si+Al+Fe‴).

E. Passaglia

Papers

The crystal chemistry of mordenites