Scandio-winchite

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Formula: ◻(NaCa)(Mg₄Sc)(Si₈O₂₂)(OH)₂
Inosilicate (chain silicate), winchite root name group, sodium-calcium amphibole subgroup, w(OH, F, Cl)-dominant amphibole group, scandium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.026 calculated for the empirical formula
Hardness: 5½
Environments

Pegmatites

Scandio-winchite is a new mineral, approved in 2022 and to date (September 2024) reported only from the type locality.

Localities

At the type locality, the Jordanów serpentinite quarry, Gmina Jordanów Śląski, Wrocław County, Lower Silesian Voivodeship, Poland, scandio-winchite, the first natural scandium-dominant amphibole mineral, has been discovered in a granitic pegmatite that crops out in close association with rodingite-like calc-silicate rocks and metasomatised granitic bodies in the serpentinite quarry. It occurs as an isolated subhedral crystal, with the size of ~20 × 8 μm² in planar section, and as three polycrystalline aggregates, up to 50 μm across, composed of needle-shaped crystals. It is present within chlorite aggregates that supposedly represent remnants of partly recrystallised xenoliths of the blackwall (blackwall rocks are hybrids as they have no pre-metamorphic equivalent of comparable chemical composition, but were formed from two different precursor rocks by tectonic mixing and/or metasomatic transfer of material - Google) chlorite schists and is in quartz-feldspar portions of the pegmatite adjoining such xenolithic assemblages.
Scandio-winchite is most likely a secondary phase of metasomatic origin related to the evolution of the country rocks and partial alteration of the blackwall chlorite schist xenolith induced by the pegmatitic melt and associated fluids (AM 109.5.940-948).
Associated minerals include zircon, xenotime-(Y), uraninite, tremolite, titanite, spessartine, rhabdophane-(Nd), quartz, pyrochlore group minerals, phenakite, muscovite, monazite-(Ce), milarite, microlite group minerals, K-feldspar, galena, fluorapatite, fersmite, euxenite-(Y), epidote, dravite, diopside, columbite-(Mn), clinozoisite, clinochlore, cassiterite, cascandite, biotite, beryl, bavenite-bohseite, allanite-(Ce), albite and aikinite (Mindat).

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