Mazzite


Mazzite Series		Mazzite-Mg \|(Mg_2.5K₂Ca_1.5) (H₂O)₃₀\| [Al₁₀Si₂₆O₇₂] Mazzite-Na \|Na₄(H₂O)₃₀\| [Al₈Si₂₈O₇₂]

Morphology:
	Hexagonal, prismatic to finely fibrous, radiating aggregates.

Physical properties:
	Cleavage: none. Hardness: 4. Density: 2.11 gm/cm³. Luster: vitreous. Streak: white.

Optical properties:
	Color: colorless. Mazzite-Mg Uniaxial (-). ω 1.506, ε 1.499, δ 0.007 Mazzite-Na Uniaxial (+). α 1.472, γ 1.471, δ 0.001
			Spray of Mazzite-Mg fibers with phillipsite and stubby offretite prisms, Mont Semiol, Montbrison, France. Field of view, 2.5 mm. © Volker Betz
Crystallography:
	Unit cell data
		Mazzite-Mg	a 18.392, c 7.646 Å Z = 1, Space group P63/mmc. (Galli 1975)
		Mazzite-Na	a 18.2343(7), c 7.6371(2) Å Z = 1, Space group P63/mmc. (Arletti et al. 2005)

Names:
	Mazzite from outcrops of olivine basalt near the top of Mont Semiol, near Montbrison, Loire, France, was described and named by Galli et al. (1974) to honor Fiorenzo Mazzi, Professor of Mineralogy at the University of Pavia, Italy. Sodium-rich mazzite from Boron, California, USA, was described and named mazzite-Na by Arletti et al. (2005). With the approval of the Commission on New Minerals, Nomenclature and Classification of the Internal Mineralogical Association the name mazzite was raised to series status and the original mazzite was renamed mazzite-Mg.

Crystal structure:
	Mazzite is closely related to the molecular sieve Ω, which was first described in Union Carbide Dutch Patent (1967). The framework of mazzite consists of edge-sharing four-ring chains that have the sequence of two tetrahedral apices up and one down (see dsc on the MAZ page), which link into a hexagonal structure. Two types of channels run parallel to the c-axis. One is confined by twelve-membered rings of tetrahedra (aperture 7.4 Å), the other by elliptical eight-membered rings (aperture 5.6 x 3.4 Å). T-O distances are consistent with (Si, Al) disorder.
	In mazzite-Mg the Mg occurs in “gmelinite-type” cages (see gme on the MAZ page) and is six-coordinated by H2O molecules. Galli (1975) speculated that the Mg-H₂O complex acts as a template for the formation of “gmelinite-type” cages. An additional cation site (occupancy about 50%) is mainly occupied by K (red in the figure) and is situated in the distorted eight-membered rings, where it is octahedrally coordinated by four framework oxygens and two H₂O molecules. Ca is located in the center of the large channels, running parallel to the c-axis and is surrounded by disordered H₂O molecules. The walls of these large channels are lined with H₂O molecules, and the cations sit at regular intervals in the middle of these H₂O pipes (Galli 1975).
	Dehydration of mazzite and accompanying cation diffusion was investigated by Rinaldi et al (1975) and Alberti and Vezzalini (1981). In mazzite-Na the only cations are Na (yellow), which are located at three different sites (Arletti et al. 2005). NaI is at the center of the 6-membered ring between adjacent gmelinite cages and is coordinated by six framework oxygens and two H₂O molecules. NaII lies on the centerline of the elliptical 8-membered ring channel and is coordinated by four framework oxygens and two H₂O molecules. NaIII occupies sites with H₂O along the walls of the 12-membered ring channel, and is coordinated with two framework oxygen atoms and four H₂O molecules.

Occurrences:
	Mazzite-Mg is presently known only from Mont Semiol, Montbrison, France, where it occurs with phillipsite, offretite, and chabazite in cavities in porphyritic olivine basalt. Mazzite-Na is known from two localities, Boron, California, USA, and the Proudette Quarry at Mont St. Hilaire, Quebec, Canada. At both localities mazzite-Na forms silky, fibrous crystals (see Weiß, 2005, for pictures of each). At Boron the mazzite-Na grew in vesicles in basalt that was saturated with Na-borate brines, and is associated with analcime, clinoptilolite-Na, phillipsite-Na, chabazite-Na, and gmelinite-Na (Arletti et al. 2005).

References:
	Alberti, A. and Vezzalini, G. (1981) Crystal energies and coordination of ions in partially occupied sites: dehydrated mazzite. Bull. Minéral. 104, 5-9. Arletti, R., Galli, E., Vezzalini, G., and Wise, W.S. (2005) Mazzite-Na, a new zeolite from Boron, California: Its description and crystal structure. Am. Mineral. 90, 1186-1191. Galli, E. (1975) Crystal structure refinement of mazzite. Rend. Soc. It. Mineral. Petrol. 31, 599-612. Galli, E., Passaglia, E., Pongiluppi, D. and Rinaldi, R. (1974) Mazzite, a new mineral, the natural counterpart of the synthetic zeolite Ω. Cont. Mineral. Petrol. 45, 99-105. Rinaldi, R., Pluth, J.J. and Smith, J.V. (1975) Crystal structure of mazzite dehydrated at 600°C. Acta Crystallogr. B31, 1603-1608. Union Carbide Co., Dutch Pat. 6,710,729 3rd August, 1967. Weiß, S. (2005) Neue Mineralien. Lapis 30, Nr. 10, 61-64. Updated: September 2025.