Images
Formula: CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH)
Cyclosilicate (ring silicate), borosilicate,
tourmaline group, forms a series with
feruvite and with fluor-uvite
(Mindat), only limited solid solution with
liddicoatite, but complete solid solution series with
dravite
(Lapis 3.11,23)
Crystal System: Trigonal
Specific gravity: 2.96 to 3.06 measured, 3.115 calculated
Hardness: 7½
Streak: Light brown
Colour: Yellowish brown, brown, blackish brown, bluish black, grey
Environments:
Uvite occurs typically in calcium-rich rocks subjected to
contact metamorphism and metasomatic processes which add
boron (HOM); it is frequently found
in marble associated with
diopside,
tremolite, phlogopite or
meonite, sometimes with quartz
(Dana, Lapis 3.23).
Other associates include calcite,
dolomite and
apatite
(HOM).
Localities
Note
The official IMA name for this mineral species was uvite; the approval, however, was withdrawn by IMA in 2018
since analysis showed that the type material may be a potentially new
oxy-tourmaline. Uvite was finally approved in 2019 with
a new type locality. Most specimens historically designated as uvite are actually, as analyses have shown,
fluor-uvite, which is much more common than uvite (Mindat).
With the exception of specimens from the Facciatoia quarry, uvite from other localities listed below are better
described as members of the fluor-uvite/uvite series.
At the type locality, the Facciatoia quarry, San Piero in Campo, Campo nell'Elba, Livorno Province, Tuscany, Italy,
uvite occurs at the centre of a 2 to 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 from Facciatoia formed by the reaction between boron-rich fluids,
released during the crystallisation process of lithium -
cesium - tantalum (LCT)
pegmatites, and the surrounding
metaserpentinites, altered by
contact metamorphism in the aureole of a
monzogranitic pluton
(MM 86.5.767-776).
At Newcomb, Essex county, New York, USA, uvite occurs as short prismatic crystals to 10 cm or as angular anhedral fragments
embedded in albite. In some specimens it has a rim of
rossmanite and/or olenite.
The following model for this mineral association is suggested:
(1) Grenville-age metamorphism: uvite, diopside,
scapolite, graphite and
phlogopite
(2) fracturing followed by invasion of aluminum- and silica-rich fluids that reacted with uvite to form
rossmanite and/or olenite; the
fluids became Na-rich toward the end of this stage and deposited albite and
quartz.
(3) low-temperature alteration of diopside and
scapolite to form tremolite
(R&M 84.4.366).
Amity, Town of Warwick, Orange county, New York, USA, is an area of
granite intrusions into
marble and associated
gneiss. The marble is
mostly composed of white crystalline calcite that often has small flakes
or spheres of graphite and
phlogopite.
Uvite/fluor-uvite occurs in
marble as brown crystals to 5 cm. It is often fluorescent a
creamy yellow colour
(R&M 96.5.441).
At the Yellow Lake south roadcut, St. Lawrence County, New York, USA, uvite occurs as small crystals and crystal
fragments embedded in or on quartz. It also occurs with
graphite in the surrounding marble
(R&M 86.4.356).
Back to Minerals