Thalliomelane, TIMn7.54+Cu0.52+O16, a new member of the coronadite group from the preglacial oxidation zone at Zalas, southern Poland

Abstract

Thalliomelane, a new member of the coronadite group (hollandite supergroup), was discovered at Zalas near Cracow in southern Poland (the southern margin of the Cracow-Silesia Monocline) in relics of a preglacial supergene mineralization disseminated in a fault breccia in Middle Jurassic sandy limestone. The mineralization formed at the expense of a sulfide assemblage, which was most likely the source of thallium, related to rejuvenation of Early-Paleozoic fault zones in the Sava phase of the Alpine orogeny. Thalliomelane occurs rarely, and exclusively in the form of fibrous and highly porous tiny aggregates < 50 µm in size that fill small fractures and voids in the sandy limestone host rock. Microprobe analyses based on 16 O and 8 octahedral cations per formula unit resulted in the mean empirical formula (Tl 0.77(10) Ba 0.21(3) K 0.03(1) Na 0.01(0) Pb 0.01(0) ) Σ1.03(7) (Mn 4+ 7.15(11) Cu 2+ 0.63(4) Co 2+ 0.08(3) Fe 3+ 0.06(3) Ni 2+ 0.03(1) Si 0. 03(2) Mg 0.01(1) ) Σ8 [O 15.67(24) (OH) 0.33(24) ], corresponding to the formula Tl(Mn 4+ 7.5 Cu 2+ 0.5 )O 16 for the thalliomelane end-member. The mineral crystallizes in the tetragonal system, space group I4/m, and has unit-cell parameters a = 9.8664(12), c = 2.8721(4) Å, V = 279.59(8) Å 3 , Z = 1. The crystal structure of thalliomelane, measured with 3D electron-diffraction, was refined to an R 1 index of 23.74%. Thalliomelane has the hollandite-type structure. The Mn 4+ cations, substituted by Cu 2+ at an amount of ~0.5 apfu, are octahedrally coordinated by oxygen atoms. Four double chains of edge-sharing (Mn,Cu)-O octahedra share corners with each other to form tunnels along the [001] direction. Tl + cations are located in the tunnels, occupying partially the origin and centre of the unit cell. The formation of thalliomelane was most probably connected to the weathering of a sulfide mineral assemblage under semi-arid to arid climate. It resulted in the release of Tl and other components of the mineralization into water under the influence of Cl-,This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

Crystal Chemistry of Thallium in Marine Ferromanganese Deposits

“…The three deepest buried nodules (≥530 cm), which contain only todorokite, 2 ppm Tl, and have 3.74 ± 0.07 ≤ Mn AOS ≤ 3.77 ± 0.08, have 50–69% Tl­(I). Overall, the higher percentage of Tl­(III) in Fe-vernadite crusts and 10 Å vernadite surface nodules (>60%) and the higher percentage of Tl­(I) in deeply buried todorokite nodules (≥50%) are consistent with (1) uptake experiments of Tl on manganates, which showed that Tl­(I) is oxidized on phyllomanganates and not on tectomanganates , and (2) the monovalent state of Tl in the tunnels of hollandite . There is also experimental evidence that the Tl oxidation is hindered on Mn­(III)-rich phyllomanganate.…”

Transformation of Hexagonal Birnessite upon Reaction with Thallium(I): Effects of Birnessite Crystallinity, pH, and Thallium Concentration

“…Within this mineral group, a relatively recent addition is thalliomelane [Tl + (Mn 7.5 4+ Cu 0.5 2+ )­O 16 ], which contains Cu­(II) in the place of Mn­(III). The more intense lines in the XRD pattern of our tectomanganate structure closely match with the ones reported for thalliomelane . The mineral formed in the present work when only Tl­(I) is made to react with birnessite is a thalliomelane-like structure, but where Mn­(III) and probably a fraction of Tl­(III) are the cations that produce the charge imbalance in the structure and Tl­(I) is most probably the balancing counterion, especially under saturation conditions (δ-MnO 2 at pH 4; see Figure B).…”

“…Application of hydrothermal-like conditions, i.e., high temperatures and pressures, shortens the required time for the conversion to tectomanganates to hours, ,,,− especially to todorokite (a 3 × 3 tunneled structure), which is the most common tunneled Mn oxide structure in nature . Neutral to alkaline conditions, higher temperatures, and weakly binding cations on the birnessite precursor, such as Ca 2+ and Mg 2+ , were found to favor the conversion to todorokite, and Na + to manjiroite (a 2 × 2 structure) …”

“…The best-fit values (goodness of fit) were obtained for the third refinement using the hollandite and the cryptomelane structures at the same time (not shown). Within this mineral group, a relatively recent addition is thalliomelane [Tl + (Mn 7.5 4+ Cu 0.5 2+ )­O 16 ], which contains Cu­(II) in the place of Mn­(III). The more intense lines in the XRD pattern of our tectomanganate structure closely match with the ones reported for thalliomelane .…”

Crystal-chemistry of sulfates from the Apuan Alps (Tuscany, Italy). VI. Tl-bearing alum-(K) and voltaite from the Fornovolasco mining complex

“…In addition, it is well known that Tl + can occur in soils, being hosted in micaceous phyllosilicates (e.g., illite; Herrmann et al 2018), and can occur as Tl + or Tl 3+ in Mn oxides. Likely, this could be the genesis of the recently approved mineral thalliomelane, TlMn 7 4+ .5 Cu 0 2+ .5 O 16 (Gołębiowska et al 2020). The description of thallium-bearing sulfates from the Fornovolasco mining complex, representing an early assemblage in the oxidation of Tl-bearing pyrite ores, suggests that thallium can be transiently sequestered by potassium sulfates during the first stages of weathering, promoting its change of speciation, from a trace element in pyrite ores (up to 1110 μg/g; D'Orazio et al 2017) to a major constituent of secondary assemblages, achieving concentrations up to some weight unit percent.…”