Ammonioleucite


Ammonioleucite		\|(NH₄,K)\| [AlSi₂O₆]

Morphology:
	Tetragonal Occurs as a replacement of analcime

Physical properties:
	Fracture: subconchoidal Hardness: not determined Density: 2.29 g/cm³ Luster: vitreous Streak: white
			Ammonioleucite from Tataruzrwu, Fujioka, Japan. Toni Wieland Collection (© Volker Betz).
Optical properties:
	Color: colorless, white Isotropic n 1.518 δ = 0.001

Crystallography:
	Space Group: I4₁/a
	Unit cell: a 13.214 Å c 13.713 Å
	Z = 16

Name:
	Hori et al. (1986) named the mineral for its composition and structural relationship with leucite. The type locality is in the Sanbagawa metamorphic belt, Tatarazawa, Fujioka, Gunma Prefecture, Japan.

Crystal structure:
	Because the X-ray powder diffraction pattern of ammonioleucite is similar to that of tetragonal leucite, Hori et al. (1986) concluded that the two minerals are isostructural. All single crystals are twinned in the same manner as leucite, but sufficient reflections were obtained to determine the space group as I4₁/a. The unit cell dimensions were calculated from the powder pattern. The figure here is a representation of the crystal structure of leucite (framework-type ANA) and probably the same as the structure of ammonioleucite with the NH₄⁺ cations occupying the K⁺ sites (green). Yamada et al. (1998) confirmed this structure through Rietveld analysis of X-ray powder diffraction data. Characterization of ammonioleucite and its deuterated form using IR spectroscopy and Rietveld refinement was reported by Andrut et al. (2004).
			The structure of tetragonal leucite of Mazzi et al. (1976) 0 < z < 0.25, to illustrate the approximate structure of ammonioleucite. The ammonium cations (green circles) occupy the K sites of leucite (or the H₂O sites of analcime), and are coordinated with six framework oxygen atoms (five are shown).

Chemical composition:

The composition is that of the ammonium-analog of leucite. The only other element in the type locality material is minor potassium. However, Tl has been found in the only other known ammonioleucite from a deep-sea occurrence (Nishida et al. 1997). An infrared absorption spectrum from the type material showed that the crystals contain no zeolitic water.


Occurrences:
	The Tatatrazawa ammonioleucite occurs near the contact between arkosic sandstone and schist that has been hydrothermally altered. Veinlets and cavities in the altered zone contain dolomite and ammonioleucite, which is a later alteration product of analcime. The source of the ammonia must have been from the hydrothermal fluids. At the present time some of the local springs and hot springs contain ammonia (Hori et al. 1986). Nishida et al. (1997) report the finding of Tl-bearing ammonioleucite in hydrothermally altered mid-ocean ridge basalt.

References:
	Andrut, M., Harlov, D.E. and Najorka, J. (2004) Characterization of ammonioleucite (NH₄)[AlSi₂O₆] and ND4 -ammonioleucite (ND₄) [AlSi₂O₆] using IR spectroscopy and Rietveld refinement of XRD spectra. Mineral. Mag. 68, 177–189. Hori, H., Nagashima, K., Yamada, M., Miyawaki, R,. and Marubashi, T. (1986) Ammonioleucite, a new mineral from Tatarazawa, Fujioka, Japan. Am. Mineral. 71, 1022-1027. Mazzi, F., Galli, E., and Gottardi, G. (1976) The crystal structure of tetragonal leucite. Am. Mineral. 61, 108-115. Nishida, N., Kimata, M. Kyono, A., Togawa, Y., Shimizu, M., and Hori, H. (1997) First finding of thallium-bearing ammonioleucite; a signal for the ultimate stage of the hydrothermal process and for a far-reaching effect from seawater alteration of MORB. Annual Rpt. Inst. of Geoscience, Univ. of Tsukuba , 23, 35-41. Yamada, M., Miyawaki, R., Nakai, I., Izumi, F., and Nagashima, K. (1998) A Rietveld analysis of the crystal structure of ammonioleucite. Mineral. Jour. 20, 105-112. Updated: April 2025.