The new mineral novograblenovite, (NH4,K)MgCl3·6H2O from the Tolbachik volcano, Kamchatka, Russia: mineral description and crystal structure

Abstract

Abstract:The new mineral novograblenovite, (NH 4 ,: 3.330 (100) (2 2 0), 2.976 (45) ( ̅ ), 2.353 (29) ( ̅ ), 3.825 (26) (2 0 2), 1.997 (25) ( ̅̅̅̅̅ 2). The density calculated from the empirical formula and the X-ray data is 1.504 g·cm -3 . The mineral is biaxial (+) with α = 1.469(2), β = 1.479(2), γ = 1.496(2) (λ = 589 nm); 2V (meas.) = 80(10) º and 2V (calc.) = 75.7º. The crystal structure (solved and refined using single-crystal X-ray diffraction data, R1 = 0.0423) is based on the perovskite-like network of (NH 4 ,K)Cl 6 -octahedra sharing chlorine vertices, and comprises [Mg(H 2 O) 6 ] 2+ groups in framework channels. The positions of all independent H atoms were obtained by difference Fourier techniques and refined isotropically. All oxygen, nitrogen and chlorine atoms are involved in the system of hydrogen bonding, acting as donors or acceptors. The formula resulting from the structure refinement is [(NH 4 ) 0.7 K 0.3 ]MgCl 3 ·6H 2 O. The mineral is named after Prokopiy Trifonovich Novograblenov, one of the researchers of Kamchatka Peninsula, a teacher, naturalist, geographer and geologist.

Novograblenovite from Radlin, Upper Silesia, Poland and its relation to ‘redikortsevite’

“…The weighted residual factor wR 2 presents a divergence of the refined crystal structure model from all recorded X-ray scattering intensities. In this study the discrepancy factor wR 2 = 5.7% is improved over twice with respect to Okrugin et al (2019), wR 2 =12.3% and 3 times compared to Zolotarev et al (2019), wR 2 =19.1%.…”

“…Chesnokov's et al's (1988) measurement gave 1.43(1) g•cm -3 . The densities calculated from single crystal X-ray diffraction experiments are 1.453 g•cm -3 (this study) and 1.504 g•cm -3 (Okrugin et al, 2019).…”

“…Therefore, phases formed by spontaneous combustion on this dump fully meet the criteria of the new IMA CMNNC guidelines and should be considered as minerals (Parafiniuk and Hatert, 2020). A mineralogical and structural study of a phase found in significant amounts at Radlin coal-dump clearly indicates that it is exactly the same mineral as novograblenovite, recently described from a volcanic exhalation in Kamchatka, Russia (Okrugin et al, 2019). Presented material forms larger, better developed crystals than those from the volcanic environment which allows us to characterize them more accurately.…”

“…Novograblenovite from Radlin like the holotype (Okrugin et al, 2019) crystallizes in monoclinic system, space group C2/c with β=90.054(3)° and 90.187(2)º, respectively.…”

New IMA CNMNC guidelines on combustion products from burning coal dumps

“…These minerals are formed in both environments in analogous circumstances, and they even form bigger and better developed aggregates on dumps than in volcanic exhalations, where they are rarely found. A submission of the phase known from the burning coal dumps as "redikortsevite" was rejected by CNMNC as being of anthropogenic origin, and the new mineral novograblenovite was accepted 3 years later for the same phase found in Kamchatka Peninsula, Russia (Okrugin et al, 2019). Today mineralogists studying burning coal dumps are not motivated to submit proposals for new minerals even though they are certain that they meet the necessary criteria (Witzke, 1997).…”