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Formula: LiMn2+4Si5O14(OH)
Inosilicate (chain silicate), forms a series with natronambulite,
lithium- and manganese- bearing mineral
Crystal System: Triclinic
Specific gravity: 3.53 measured, 3.55 calculated
Hardness: 6½
Streak: Pale yellow
Colour: Pale tan to orange-brown to deep red
Common impurities: Ti,Al,Fe,Mg,Ca,K,H2O,C,P
Environments
Localities
At Obernberger Tribulaun, Obernberg am Brenner, Innsbruck-Land District, Tyrol, Austria, the first discovery of
nambulite in Austria
was made in 2018. The deposit consists of small lenses containing a variety of
manganese-bearing minerals in
quartzitic metamorphosed
radiolarite. The
nambulite occurs as irregular, small, orange-yellow masses up to several centimeters infilling fractures
(R&M 95.6.532).
At the Figuerinha Mine, Urucum massif, Corumbá, Mato Grosso do Sul, Brazil, bright orange fibrous nambulite
to 1 cm in radially oriented
clusters occurs. It forms in thin veinlets to 30 mm associated with
K-feldspar,
baryte and calcite. These are
hosted in massive
braunite-rich ore, originally formed by
primary
sedimentary processes but modified by later metamorphism
(http://www.mme.gov.na/files/publications/759_Schneider_Nambulite.pdf, R&M 95.6.532-533).
At the Cerchiara Mine, Borghetto di Vara, La Spezia Province, Liguria, Italy, small, pale pink to off-white
nambulite crystals occur.
Braunite and hematite are the
two main ore minerals
(R&M 95.6.532).
At the type locality, the Funakozawa mine, Ono, Hirono-cho, Kunohe-gun, Iwate Prefecture, Japan, nambulite
occurs
in veinlets cutting braunite ore in
chert. Associated minerals include
braunite, albite,
neotocite and
rhodochrosite
(HOM).
At the Tunakozawa mine, Kitakami Mountains, Iwate Prefecture, Japan, nambulite occurs in veinlets up to
5 cm thick that cut
braunite ore in chert.
Associated minerals include
albite, neotocite and
rhodochrosite
(AM 58.1112).
At the Kombat Mine, Kombat, Grootfontein, Otjozondjupa Region, Namibia, a hydrothermal vein system cuts through
the layering of manganese ore bodies. The nambulite-bearing
veins are up to 10 cm thick and contain prismatic, light red crystals up to 3 x 4 x 2 mm3, as well
as small, fibrous, pink crystals. Matrix specimens consist primarily of
gypsum with scattered
nambulite crystals embedded therein. On the contact surfaces with the nambulite, the
gypsum
is replaced by acicular brown brushite, and inclusions of
cahnite
are common in the gypsum. Rare, small, yellow-brown prismatic crystals of
kentrolite are present as are
baryte and
calcite. The nambulite crystals are the finest known and vary in
size from a few millimeters
to 3 cm. They are typically vibrant red and translucent to transparent
(R&M 95.6.530-534, http://www.mme.gov.na/files/publications/759_Schneider_Nambulite.pdf).
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