Rongibbsite, Pb2(Si4Al)O11(OH), a new zeolitic aluminosilicate mineral with an interrupted framework from Maricopa County, Arizona, U.S.A.

Abstract

A new zeolitic aluminosilicate mineral species, rongibbsite, ideally Pb 2 (Si 4 Al)O 11 (OH), has been found in a quartz vein in the Proterozoic gneiss of the Big Horn Mountains, Maricopa County, Arizona, U.S.A. The mineral is of secondary origin and is associated with wickenburgite, fornacite, mimetite, murdochite, and creaseyite. Rongibbsite crystals are bladed (elongated along the c axis, up to 0.70 × 0.20 × 0.05 mm), often in tufts. Dominant forms are {100}, {010}, {001}, and {101}. Twinning is common across (100). The mineral is colorless, transparent with white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼5; cleavage is perfect on {100} and no parting was observed. The calculated density is 4.43 g/cm 3 . Optically, rongibbsite is biaxial (+), with n α = 1.690, n β = 1.694, n γ = 1.700, c Z = 26°, 2V meas = 65(2)°. It is insoluble in water, acetone, or hydrochloric acid. Electron microprobe analysis yielded an empirical formula Pb 2.05 (Si 3.89 Al 1.11 )O 11 (OH).Rongibbsite is monoclinic, with space group I2/m and unit-cell parameters a = 7.8356 (6), b = 13.913(1), c = 10.278(1) Å, β = 92.925(4)°, and V = 1119.0(2) Å 3 . Its structure features an interrupted framework made of three symmetrically distinct TO 4 tetrahedra (T = Si + Al). The framework density is 17.9 T per 1000 Å 3 . Unlike many known interrupted frameworks in zeolite-type materials, which are usually broken up by OH or F, the framework in rongibbsite is interrupted by O atoms. There are various corner-shared tetrahedral rings in the framework of rongibbsite, including two types of 4-membered, three 6-membered, and one 8-membered rings. The extraframework Pb and OH reside alternately in the channels formed by the 8-membered rings. The Pb cations are disordered over two split sites, Pb and Pb′, with site occupancies of 0.8 and 0.2, respectively, and a Pb-Pb′ distance of 0.229 Å, providing a structural explanation for the two strong Raman bands (at 3527 and 3444 cm -1 ) attributable to the O-H stretching vibrations. The average bond lengths for the T1, T2, and T3 tetrahedra are 1.620, 1.648, and 1.681 Å, respectively, indicating that the preference of Al for the three tetrahedral sites is T3 >> T2 > T1. Rongibbsite represents the first natural aluminosilicate with Pb as the only extraframework cation.

Meierite, A New Barium Mineral With A Kfi-Type Zeolite Framework From the Gun Claim, Yukon Canada

“…Below 200 cm -1 , the bands are related to the rotational and translational modes of TO 4 tetrahedra, as well as lattice vibrational modes. Similar to other zeolite-type structures (e.g., Yang et al 2013), in meierite the Raman bands associated with the T-O symmetric stretching vibrations are less intense than those corresponding to the T-O asymmetric stretching modes due to the complex vibrations of the TO 4 tetrahedra coupled through sharing of the O at the corners (Wopenka et al 1998). In contrast, isolated TO 4 tetrahedra usually have symmetric stretching vibrations more intense than the asymmetric stretching modes.…”

“…The Raman spectrum of meierite is shown in Figure 7. Based on previous Raman spectroscopic studies of various zeolites (Dutta & Zaykoski 1988, Smirnov et al 1994, Knops-Gerris et al 1997, Goryainov & Smirnov 2001, Yu et al 2001, Liu et al 2012, Yang et al 2013, we made a tentative assignment of major Raman bands for meierite. The O-H stretching vibrations bands are located between 3100 and 3680 cm -1 .…”

Microwave-assisted method for the direct synthesis of nano-sized Cu-zeolite

“…Dominant bands in the region 250 -550 cm −1 originate from the T−O−T bending vibrations. The bands below 250 cm −1 are frequently associated with the rotational and translational modes of TO 4 tetrahedra, as well as the lattice vibrational modes (Yang et al, 2012). It has been reputed that the wavenumbers of Raman bands attributed to the T−O−T bending modes are inversely correlated to the tetrahedral ring size, as well as the Si/Al ratio is (Wopenka et al, 1998;Yu et al, 2001;Yang et al, 2013).…”