Celleriite, ☐(Mn22+Al)Al6(Si6O18)(BO3)3(OH)3(OH), a new mineral species of the tourmaline supergroup

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Uvite, CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH), is a new mineral of the tourmaline supergroup. It occurs in the Facciatoia quarry, San Piero in Campo, Elba Island, Italy (42°45′04.55″N, 10°12′50.89″E) at the centre of a narrow (2–3 cm wide) vein composed of aggregates of dark brown to black tourmaline, penetrating (magnesite + dolomite)-rich hydrothermally altered metaserpentinite. Crystals are euhedral and up to 1 cm in size, brown with a vitreous lustre, conchoidal fracture and grey streak. Uvite has a Mohs hardness of ~7½, a calculated density of 3.115 g/cm3 and is uniaxial (–). Uvite has trigonal symmetry, space group R3m, a = 15.9519(10) Å, c = 7.2222(5) Å, V = 1597.3(1) Å3 and Z = 3. The crystal structure was refined to R1 = 1.77% using 1666 unique reflections collected with MoKα X-rays. Crystal-chemical analysis resulted in the empirical crystal-chemical formula $^X ({\rm Ca}_{0.61}{\rm Na}_{{0.35}} \square_{{0.04}})_{\Sigma 1.00}{}^{Y} \left( {{\rm Mg}_{1.50}{\rm Fe}^{2 + }_{0.47} {\rm Al}_{0.71}{\rm Fe}^{3 + }_{0.14} {\rm Ti}_{0.18}} \right)_{\Sigma 3.00}$ ${}^{Z} \left( {{\rm Al}_{4.54}{\rm Fe}^{3 + }_{0.18} {\rm V}^{3 + }_{0.02} {\rm Mg}_{1.27}} \right)_{\Sigma 6.00}{}^{T}\left[ {{\left( {{\rm Si}_{5.90}{\rm Al}_{0.10}} \right)}_{\Sigma 6.00}{\rm O}_{18}} \right]{\rm } \left( {\rm BO_3} \right)_3^{} {^{\rm O(3)}}\left( {\rm OH} \right)_3{}^{{\rm O}\left( 1 \right)} [\left( {\rm OH} \right)_{0.55}{\rm F}_{0.05}{\rm O}_{0.40}]_{\Sigma 1.00}$ which recast in its ordered form for classification purposes is: $$\eqalign{& ^{\rm X} ({\rm Ca}_{0.61}{\rm Na}_{0.35}\squ _{0.04})_{\Sigma 1.00}{}^{\rm Y} \left( {{\rm Mg}_{2.35}{\rm Fe}^{2 + }_{0.47} {\rm Ti}_{0.18}} \right)_{\Sigma 3.00} \cr & {}^{\rm Z} \left( {{\rm Al}_{5.25}{\rm Fe}^{3 + }_{0.32} {\rm V}^{3 + }_{0.02} {\rm Mg}_{0.42}} \right)_{\Sigma 6.00}{}^{\rm T} \left[ {{\left( {{\rm Si}_{5.90}{\rm Al}_{0.10}} \right)}_{\Sigma 6.00}{\rm O}_{18}} \right]{\rm }\left( {\rm BO_3} \right)_3{}^{\rm V} \left( {\rm OH} \right)_3{}^{\rm W} [\left( {\rm OH} \right)_{0.55}{\rm F}_{0.05}{\rm O}_{0.40}]_{\Sigma 1.00}}$$ Uvite is a hydroxy-species belonging to the calcic-group of the tourmaline supergroup. The closest end-member compositions of valid tourmaline species are fluor-uvite and feruvite, to which uvite is related by the substitutions W(OH)– ↔ WF– and YMg2+ ↔ YFe2+, respectively. The occurrence of a solid-solution between uvite and magnesio-lucchesiite, according to the substitution ZMg2+ + W(OH)– ↔ ZAl3+ + WO2–, is supported by experimental data. The new mineral was approved by the IMA–CNMNC (IMA 2019-113). Uvite from Facciatoia formed by the reaction between B-rich fluids, released during the crystallisation process of LCT pegmatites, and the surrounding metaserpentinites, altered by contact metamorphism in the aureole of the Miocene Mt. Capanne monzogranitic pluton.

Section: Calcic Tourmalines From the Thermal Aureole Of The Monte Cap...mentioning

confidence: 80%

Uvite, CaMg₃(Al₅Mg)(Si₆O₁₈)(BO₃)₃(OH)₃(OH), a new, but long-anticipated mineral species of the tourmaline supergroup from San Piero in Campo, Elba Island, Italy

Bosi

Biagioni²,

Pezzotta³

et al. 2022

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“…The crystallising tourmaline registered this event with a bluish growth zone slightly richer in Fe 2+ , which ceased to grow when no more Fe was available in the system. This partial opening of the geochemical system is probably similar, but much less developed than the one associated with the formation of the well-known black-cap tourmaline crystals from Elba pegmatites (Bosi et al, 2022a). This system is likely related to more or less extensive fracturing and even pocket collapse before the end of the cavity crystallization, when abundant and reactive fluids were still present.…”

Section: Petrogenesis and Evolution Of The Blue-growth Zones In Tourm...mentioning

confidence: 85%

Blue growth zones caused by Fe²⁺ in tourmaline crystals from the San Piero in Campo gem-bearing pegmatites, Elba Island, Italy

Altieri

Pezzotta²,

Skogby

et al. 2022

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Two tourmaline crystals with a blue-growth zone at the analogous pole, respectively from the San Silvestro and the Fucili pegmatites, located in the San Piero in Campo village, Elba Island (Tyrrhenian Sea, Italy), have been described for the first time through chemical and spectroscopic analyses to define their crystal-chemical aspects and the causes of the colour. Chemical data obtained by electron microprobe analysis indicate that both tourmalines belong to the elbaite-fluorelbaite series. The upper part of each crystal is characterized by an increased amount of Fe (FeO up to ⁓1 wt%) and a Ti content below the detection limit. Optical absorption spectra recorded on the blue zone of both samples show absorption bands caused by spin-allowed d-d transitions in [6]coordinated Fe 2+ , and no IVCT Fe 2+ -Ti interactions, indicating that Fe 2+ is the only colour-causing agent. Mössbauer analysis performed on the blue zone of the Fucili sample confirmed the Fe 2+

“…Cavities found at shallower levels contain dark-coloured tourmalines, together with pale-blue aquamarine and spessartine. On the contrary, cavities found at deeper levels contain abundant polychrome and rose tourmalines with variable Mn and Fe content, morganite, petalite, pollucite and spessartine (Orlandi and Pezzotta, 1996;Pezzotta, 2000;Bosi et al, 2022).…”

Section: Occurrence and Sample Descriptionmentioning

confidence: 99%

“…Additionally, Felch et al (2016) inferred that the observed corrosion and leaching of cavity-lining spessartine garnet crystals, was the result of reactions with late-stage hydrothermal fluids that originated and migrated from adjacent highly evolved miarolitic cavities. More recently, Bosi et al (2022) and Altieri et al (2022) proposed that the pocket rupture event, possibly related to thermal contraction during the cooling of the rock, led to some mechanical brittle deformations of the enclosing pegmatite through the formation of late-stage fractures. This allowed the highly-reactive late-stage cavity fluids to permeate the fractures surrounding the cavity where the early-crystallised cavity-lining and-coating Fe-and Mn-rich minerals were hosted.…”

Section: Introductionmentioning

confidence: 99%

Dark-coloured Mn-rich overgrowths in an elbaitic tourmaline crystal from the Rosina pegmatite, San Piero in Campo, Elba Island, Italy: witness of late-stage opening of the geochemical system

Altieri

Pezzotta²,

Skogby

et al. 2022

Self Cite

Multicoloured tourmalines from Elba Island quite frequently display dark-coloured terminations due to the incorporation of Fe, but also occasionally Mn, formed during the latest-stages of crystallisation in cavities. However, the mechanisms that led to the availability of these elements in the late-stage residual fluids are not yet completely clear. For this purpose, we studied a representative tourmaline crystal found naturally disrupted in two fragments within a wide miarolitic cavity in the Rosina pegmatite (San Piero in Campo, Elba Island, Italy), and characterised by late-stage dark-coloured overgrowths. Microstructural and paragenetic observations, as well as chemical and spectroscopic analyses (electron microprobe and optical absorption spectroscopy), provide evidence that the formation of the observed dark-coloured Mn-rich overgrowths is the https://doi.org/10.1180/mgm.2022.125 Published online by Cambridge University Press result of a pocket rupture. This event allowed chemical alteration of the cavity-coating spessartine garnet by highly-reactive late-stage cavity fluids through leaching processes, with the subsequent release of Mn to the residual fluids. We argue that the two fragments were originally a single crystal, which underwent a natural breakage followed by the simultaneous growth of Mn-rich dark terminations at both breakage surfaces. This supports the pocket rupture event, responsible for both the shattering of the tourmaline crystal and the chemical variation of the cavity-fluids through the availability of Mn, which was incorporated by tourmaline crystals. Additionally, a comparison of the dark overgrowths formed at the analogous and the antilogous poles, can provide additional information on tourmaline crystallisation process at the two different poles. The antilogous pole is characterised by a higher affinity for Ca, F and Ti, and a selective uptake of Mn 2+ even in the presence of considerable amount of Mn 3+ in the system. This uneven uptake of Mn ions caused the yellow-orange colouration of the antilogous overgrowth (Mn 2+ dependent) instead of the purplereddish colour displayed by the analogous overgrowths (Mn 3+ dependent).