Formula: NaFe2+3Al6(Si6O18)(BO3)3(OH)3F
Cyclosilicate (ring silicate), borosilicate,
tourmaline group, forms a complete solid solution with
schorl
Crystal System: Trigonal
Specific gravity: 3.20 measured, 3.27 calculated
Hardness: 7
Streak: Bluish white
Colour: Black
Luminescence: Not fluorescent
Environments
Pegmatites
Hydrothermal environments
Fluor-schorl is a relatively new mineral, approved in 2011.
Localities
There are two co-type localities, Steinberg, Zschorlau, Erzgebirgskreis, Saxony, Germany, and Le Cave, Franzensfeste,
Wipptal, South Tyrol, Trentino-Alto Adige, Italy.
At the Lake Boga granite quarry, Lake Boga, Swan Hill Rural City, Victoria, Australia, fluor-schorl occurs as
black-brown, crude prisms, associated with quartz and
feldspar, from a
pegmatite patch in the
granite
(EJM 28.163-177).
At the Fluorite locality, Nedvědice, Brno-Country District, South Moravian Region, Czech Republic, a black prism
of fluor-schorl was found in a granite
pegmatite
(EJM 28.163-177).
At Epprechtstein, Kirchenlamitz, Wunsiedel im Fichtelgebirge, Upper Franconia, Bavaria, Germany, a black prism of
fluor-schorl was found in a granite
pegmatite, associated with pale greenish hexahedra of
fluorite and yellowish to ivory-coloured
K-feldspar crystals
(EJM 28.163-177).
At the Roter Berg mining district, Zschorlau, Erzgebirgskreis, Saxony, Germany, fluor-schorl was found as
dark brown, subparallel prisms in quartz
(EJM 28.163-177).
At Steinberg, Zschorlau, Erzgebirgskreis, Saxony, Germany (one of the co-type localities), fluor-schorl was
found in the alluvial tin deposits. It was formed as a pneumatolytic phase and in
high-temperature hydrothermal veins in granitic
pegmatites. All of the fluor-schorl that is considered
pneumatolytic occurs in areas with tin mineralisation.
The fluor-schorl is closely associated with quartz,
biotite, albite,
orthoclase, schorl,
cassiterite and wolframite.
Fluor-schorl occurs typically as striated prismatic crystals, up to 1 x 10 mm, that are often radially arranged
and found in small quartz veins intergrown with
quartz and feldspar, and rarely grown
on quartz crystals
(EJM 28.163-177).
Other associated minerals include apatite,
beryl, fluorite,
axinite, epidote,
pyrrhotite, molybdenite,
galena, chalcopyrite,
pyrite, zoisite,
garnet, prehnite,
muscovite, talc,
chlorite, chabazite,
stilbite, laumontite,
apophyllite and calcite
(Mindat).
At Le Cave, Franzensfeste, Wipptal, South Tyrol, Trentino-Alto Adige, Italy, (one of the co-type localities),
fluor-schorl was formed as a pneumatolytic phase and in high-temperature hydrothermal veins in a
granitic
pegmatite. Small veins in this
pegmatite contain quartz
crystals (up to 1 cm in length) with tiny prismatic tourmaline crystals
grown on their top. These tourmaline crystals show a pale brownish to pale
greyish-bluish colour and have a maximum size of 1 mm. Similar fluorine-rich, prismatic
tourmalines are locally intergrown with
quartz, have a brown-black colour, show strong dichroism, and reach a size of up
to 8 mm. There appear to be two different phases of development in the
pegmatitic body: a pneumatolytic phase and a hydrothermal
phase. The pneumatolytic phase includes fluor-schorl as well as
fluorite, axinite,
epidote, pyrrhotite,
molybdenite, galena,
chalcopyrite and pyrite.
Fluor-schorl occurs as prismatic crystals, up to 5 x 10 mm, intergrown with
quartz and rarely grown on quartz
crystals. The hydrothermal phase includes zoisite,
garnet, prehnite,
albite, muscovite,
talc, chlorite,
chabazite,
stilbite, laumontite,
apophyllite and calcite
(EJM 28.163-177).
At the Erongo Region, Namibia, several samples of fluor-schorl have been found as black prisms, associated with
pale greenish, rounded (corroded) octahedral fluorite crystals,
minor (hydroxyl-?)herderite, and
schorl from the famous granite
pegmatites. Also a thick black prism of fluor-schorl
has been found, associated with reddish K-feldspar, from the Mile 72
pegmatite, Swakopmund
(EJM 28.163-177).
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