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almandines

Almandines are the iron-rich member of the garnet group with the chemical formula Fe3Al2Si3O12. They are commonly the dark red to purplish-red garnet used as gemstones; the term almandine is often used to denote gem-grade material of this composition.

Almandine crystallizes in the isometric system and forms euhedral to subhedral crystals, typically dodecahedra or trapezohedra.

Almandine forms under medium to high-grade metamorphic conditions, particularly in aluminous pelitic rocks during regional metamorphism.

The name almandine derives from almandin, with origins traceable to historic sources; it is commonly linked

It
has
a
vitreous
luster,
a
hardness
of
about
6.5–7.5
on
the
Mohs
scale,
and
a
specific
gravity
of
roughly
3.9–4.3.
The
gemstone
can
be
transparent
to
translucent
and
shows
a
characteristic
deep
red
color
attributable
to
iron
content.
It
occurs
in
granulite
and
schist
belts
and
is
commonly
found
with
minerals
such
as
kyanite,
sillimanite,
and
staurolite.
Almandine
is
widely
distributed
in
metamorphic
terrains
around
the
world
and
is
a
common
component
of
garnet
assemblages.
to
the
ancient
town
of
Alabanda
in
Asia
Minor,
though
the
exact
derivation
is
uncertain.
In
addition
to
gemstones,
almandine
garnet
is
used
as
an
abrasive
and
in
various
industrial
applications.