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Formula: Na(Fe2+2.5Ti0.5)Al6(Si6O18)(BO3)3(OH)3O
Cyclosilicate (ring silicate), tourmaline group,
titanium- and boron- bearing mineral
Crystal System: Trigonal
Colour: Dark brown
Environments
Dutrowite is a relatively new mineral, approved in 2019.
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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