Dutrowite

dutrowite

tourmaline

titanium

greenschist

Images

Formula: Na(Fe²⁺_2.5Ti_0.5)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃O
Cyclosilicate (ring silicate), tourmaline group, titanium- and boron- bearing mineral
Crystal System: Trigonal
Colour: Dark brown
Environments

Metamorphic environments

Dutrowite is a new mineral, approved in 2019 and to date (June 2023) reported only from the type locality.

Localities

At the type locality, the Fornovolasco metarhyolite formation, Fornovolasco, Vergemoli, Lucca Province, Tuscany, Italy, the formation is a metarhyolite metamorphosed up to greenschist facies conditions. In the holotype material, dutrowite is associated with an intermediate member of the iron-rich dravite–oxy-dravite series, quartz, sericitised K-feldspar, rutile, ilmenite, zircon and relicts of phenocrysts. The relicts are composed of partially chloritised biotite and sericitised plagioclase. Tourmaline grain aggregates show a significant chemical variation, with dutrowite portions localised at the contact with partially chloritised biotite. The local replacement of magmatic biotite provides enough titanium to stabilise the titanium-rich tourmaline. Dutrowite is the tourmaline richest in titanium reported to date (R&M 97.6.568-569).

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