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Mikenewite, the natural analogue of synthetic α-Mn2+(S4+O3)⋅3H2O, a new sulfite mineral from the Ojuela mine, Mapimí, Mexico

Published online by Cambridge University Press:  19 April 2023

Hexiong Yang*
Affiliation:
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, AZ, USA
Robert A. Jenkins
Affiliation:
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, AZ, USA
James A. McGlasson
Affiliation:
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, AZ, USA
Ronald B. Gibbs
Affiliation:
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, AZ, USA
Robert T. Downs
Affiliation:
Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, AZ, USA
*
Corresponding author: Hexiong Yang; Email: hyang@arizona.edu
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Abstract

A new mineral species, mikenewite (IMA2022-102), ideally Mn2+(S4+O3)⋅3H2O, has been discovered from the San Judas Chimney, Ojuela mine, Mapimí, Durango, Mexico. It occurs as spheres of platy crystals. Associated minerals include goethite, cryptomelane, adamite and lotharmeyerite. Mikenewite is yellowish in transmitted light, transparent with a white streak and vitreous lustre. It is brittle and has a Mohs hardness of 2½–3. Cleavage is perfect on {101}. The measured and calculated densities are 2.48(5) and 2.467 g/cm3, respectively. Optically, mikenewite is biaxial (+), with α = 1.606(5), β = 1.614(5), γ = 1.627(1) (white light), 2V(meas.) = 69(3)° and 2V(calc.) = 77°. An electron microprobe analysis yielded an empirical formula (based on 6 O apfu) of (Mn0.86Zn0.12Fe0.04Ca0.02)Σ1.04(S0.98O3)⋅3H2O, which can be simplified to (Mn,Zn,Fe)(SO3)⋅3H2O.

Mikenewite is the natural analogue of synthetic α-Mn2+(S4+O3)⋅3H2O, as well as the Mn-analogue of albertiniite, Fe2+(S4+O3)⋅3H2O. It is monoclinic, with space group P21/n and unit-cell parameters a = 6.6390(3), b = 8.8895(4), c = 8.7900(4) Å, β = 96.095(2)°, V = 515.83(4) Å3 and Z = 4. The crystal structure of mikenewite is characterised by each Mn atom coordinated octahedrally by six O atoms, three from different sulfite O atoms and three from H2O molecules. Each S4+O3 group is bonded to three Mn atoms, resulting in a sheet parallel to (101) with the sheet composition of Mn2+(S4+O3)⋅3H2O. Such sheets, stacked along [10$\bar{1}$], are joined together by hydrogen bonds, accounting for the perfect cleavage of the mineral. Mikenewite is dimorphous with orthorhombic Pnma gravegliaite, as albertiniite is with fleisstalite. Its discovery from the Ojuela mine, which is particularly rich in Zn, implies the possibility of finding Zn-bearing sulfites there as well.

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This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
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Copyright © University of Arizona, 2023. Published by Cambridge University Press on behalf of The Mineralogical Society of the United Kingdom and Ireland
Figure 0

Table 1. List of IMA approved minerals containing the sulfite anionic group (S4+O3)2–.

Figure 1

Figure 1. The specimen on which the new mineral mikenewite was found (Specimen number R210021).

Figure 2

Figure 2. A microscopic view of yellow spheres made of platy mikenewite crystals (Specimen number R210021).

Figure 3

Figure 3. A back-scattered electron image of aggregates (spheres) of platy mikenewite crystals (Specimen number R210021).

Figure 4

Table 2. Analytical chemical data (in wt.%) for mikenewite.

Figure 5

Table 3. Powder X-ray diffraction data (d in Å, I in %) of mikenewite.*

Figure 6

Table 4. Comparison of crystallographic data of mikenewite with related minerals.

Figure 7

Table 5. Fractional atomic coordinates and equivalent isotropic displacement parameters (Å2) for mikenewite.

Figure 8

Table 6. Atomic displacement parameters (Å2) for mikenewite.

Figure 9

Table 7. Selected bond distances (Å) for mikenewite and gravegliaite.

Figure 10

Table 8. Hydrogen-bond geometry (Å, °) in mikenewite (D = donor, A = acceptor).

Figure 11

Table 9. Bond-valence sums for mikenewite.

Figure 12

Figure 4. Crystal structure of mikenewite, showing a sheet [‖(101)] consisting of [MnO3(H2O)3] octahedra (green) connected by (S4+O3)2– groups. Red, aqua, yellow and small blue spheres represent O from (S4+O3)2–, O from H2O, S and H atoms, respectively. Drawn using XtalDraw (Downs and Hall-Wallace, 2003).

Figure 13

Figure 5. Crystal structure of mikenewite, showing the stacking of sheets consisting of [MnO3(H2O)3] octahedra (green) connected by (S4+O3)2– groups. Two sheets are specifically indicated by the zigzag purple lines. These sheets are stacked along [1 0 $\bar{1}$] and are linked together by hydrogen bonds. Drawn using XtalDraw (Downs and Hall-Wallace, 2003). The legends are the same as in Fig. 4.

Figure 14

Figure 6. Raman spectrum of mikenewite, along with that of albertiniite (taken from Vignola et al., 2016) for comparison.

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