Perlialite


Perlialite		\|(K₉Na (Ca,Sr) (H₂O)₁₅\| [Al₁₂Si₂₄O₇₂]

Morphology:
	Masses or cluster of very thin hexagonal fibers.

Physical properties:
	Cleavage: unknown. Hardness: 4 - 5. Density: 2.14 gm/cm³. Luster: vitreous. Streak: white.
			Perialite crystals from Loparskaya Valley, Yukspor Mt, Khibiny Massif, Murmansk Oblast, Russia. Field of view 10 mm. Zeolite Collection of Volker Betz. Copyright: © Volker Betz (2008)
Optical properties:
	Color: colorless to gray. Uniaxial (+). ω 1.479 – 1.483, ε 1.488 – 1.489, δ 0.005 – 0.010

Crystallography:
	Unit cell data: a 18.490 - 18.543, c 7.51 - 7.531 Z = 1, Space Group P6/mmm (Artioli and Kvick 1990)



Name:
	Perlialite was named by Men’shikov (1984) in honor of Lily Alekseevna Perekrest, instructor of mineralogy at the Kirov Mining School. The type locality is at Mt. Yukspor, Khibina massif, Kola Peninsula, Russia.

Crystal structure:
	The framework topology (Artioli and Kvick 1990) is the same as for synthetic Linde Type L (LTL) as determined by Barrer and Villiger (1969). Two types of channels run parallel to the c-axis. One is bounded by twelve-membered rings of the ltl cages (aperture 7.1 Å), and the other is bounded by strongly compressed eight-membered rings (aperture 3.4 x 5.6 Å). T-O distances give no indication of (Si,Al) order. When comparing the structural diagrams for mazzite and perlialite projected to the c-axis, strong similarities are evident. However, in perlialite six-membered double-rings connect the sheets, whereas single rings occur in mazzite. Thus, in perlialite six-membered rings (double 6-rings) connect two cancrinite-type cages (LTL), and in mazzite six-membered rings connect two gmelinite cages.
	The powder sample used for structure refinement (Artioli and Kvick 1990) was separated with thallium malonate heavy liquid. Thus, perlialite became partly ion-exchanged and approached the composition K₈Tl₄[Al₂Si₂₄O₇₂]•20H₂O. K was located in the cancrinite cage (fully occupied) and in the center of the six-membered double rings (occupancy 20%). Cations in the large channels bonded to the six framework oxygens of the eight-membered rings and additional H₂O molecules which fill the interior of the twelve-membered ring channels.
	Notice the different arrangement of cations and H₂O in the wide channels compared with mazzite. The second most preferred non-framework site (fully occupied) is in the compressed eight-membered rings, forming channels parallel to the c-axis. The temperature-induced structural changes in the synthetic counterpart of perlialite was investigated by Gigli et al. (2013) and Precisvalle et al. (2023). Strong pressure-induced over-hydration is observed when compressed in penetrating pressure transmitting media (Gigli et al. 2019).

Chemical composition:
	Analyses of perlialite from the two localities have similar compositions. T_Si is 0.675 and 0.650, K is about 9 cations per unit cell, and Na about one per unit cell. Ca, Mg, Ba, and Sr varying considerably, but appear to occupy one cation site per unit cell. Synthetic Zeolite L typically has the composition K₉Na₃Al₉Si₂₇O₇₂•21H₂O (Barrer and Villiger 1969) The H₂O content shows some variation between the two samples, 9.52 and 11.0 weight percent, which may be expected from the disorder in the ltl cages.

Occurrences:
	There are presently two known occurrences of perlialite, and both are associated with pegmatite dikes in alkaline massifs in Russia. At Mt. Eveslogchorr and Mt. Yukspor in the Khibiny massif, Kola Peninsula perlialite is in nepheline-microcline and sodalite-microcline cataclastic pegmatoid veins, where it is associated with pectolite, kalsilite, aegerine, wadeite, and yuksporite (Men’shikov 1984, Khomyakov 1995). Perlialite occurs as white, fibrous vein fillings at Chioiny, Kola Peninsula (Tschernich 1992) and at the Murun massif, Transbaikalia (Konev et al. 1986).

References:
	Artioli, G. and Kvick, Å. (1990) Synchrotron X-ray Rietveld study of perlialite, the natural counterpart of syntheic zeolite-L. Eur. J. Mineral. 2, 749-759. Barrer, R.M. and Villiger, H. (1969) The crystal structure of the synthetic zeolite L. Z. Kristallogr. 128, 352-370. Gigli, L., Arletti, R., Quartieri, S., Di Renzo, F. and Vezzalini, G. (2013) The high thermal stability of the synthetic zeolite K–L: Dehydration mechanism by in situ SR-XRPD experiments. Microporous mesoporous mater., 177, 8-16. Gigli, L., Vezzalini, G., Quartieri, S. and Arletti, R. (2019) Compressibility behavior and pressure-induced over-hydration of zeolite KAlSi-L. Microporous mesoporous mater. 276, 160-166. Khomyakov, A.P. (1995) Mineralogy of hyperagpaitic alkaline rocks. Clarendon Press, Oxford. 223 pp. Konev, A.A., Sapozhnikov, A.N., Afonia, G.G., Vorob’ev, E.I., Arsenyuk, M.I., and Lapides, I.L. (1986) Perlialite from the Murun Alkaline Massif. Zap. Vses. Mineral. Obshchest. 115, 200-204. Men’shikov, Yu.P. (1984) Perlialite, K₉Na(Ca,Sr)[Al ₁₂Si₂₄O₇₂]•15H₂O, a new potassium zeolite from the Khibina Massif. Zap. Vses. Mineral. Obshchest. 113, 607-612. Precisvalle, N., Beltrami, G., Ardit, M., Giacobbe, C., Pasti, L., Chenet, T. and Martucci, A. (2023) Temperature-Induced Structural Changes in Acidic L-Zeolite: An In Situ Synchrotron Time-Resolved Powder Diffraction Study. J. Phys. Chem., 127(27), 13276-13285. Tschernich, R.W. (1992) Zeolites of the World, Geoscience Press, Phoenix, Arizona. 563 pp. Updated: November 2025.