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Garnet Group: The Colors and Varieties of Garnet, ESTUDENTS: Ceiner…
Garnet Group: The Colors and Varieties of
Garnet
The Garnet Group
Aluminun Members
ALMANDINE
PYROPE
SPESSARTINE
MIXED VARIETIES: ( Rhodolite, Malaya )
Garnet is not a single mineral, but describes a group of several closely related minerals. All species of garnets possess similar physical properties and crystal forms, but differ in
chemical composition.
According The whether The Y or The X component in The chemical composition of The
species is constant, we can divide The Members of The Garnet family into two groups.
Pyralspites (Pyrope, Almandine, Spessartite) aluminium in Y site
Ugrandites (Uvarovite, Grossular, Andradite) calcium in X site
Calcium Nembers
ANDRADITE
GROSSULAR
UVAROVITE
Because The chemical composition of Garnet varies, The atomic Bonds in some species are stronger than in others. As a result, this mineral group show a range of hardness on The Mohs scale of about 6.5/7.5
Almandine
Almandine Garnet Crystal with Muscovite crystals on the side. From Gilgit, Gilgit
District, Northern Areas, Pakistan. Photo: mardani Fine Minerals Almandine is the most common Garnet. The almandine crystal formula
is: Fe3Al2(SiO4)3. Magnesium substitutes for the iron with increasingly pyrope-rich composition. Almandine range in color from Dark red to black. t is frequently cut with
a convex face, or en cabochon, and is then known as carbuncle.
Pyrope
Pyrope is the only member of the garnet family to always display red colouration in natural samples. Pyrope is especially noted for its transparency and frequent lack of flaws or inclusions.
Rhodolite is the purple variety of pyrope-almandine. The name and color come from the flower of the rhodondendron. It is often regarded as a variety of Pyrope.
Malaia garnet (or malaya) is the red-orange variety of pyrope-spessartite discovered in the 1970's in Kenia as a by product of rhodolite.
Spessartine
Spessartite is an orange to red form of the gemstone Garnet. Spessartite is a
nesosilicate, manganese aluminium garnet species, Mn²⁺₃Al₂(SiO₄)₃.
Andradite
Andradite is a calcium-iron garnet, Ca3Fe2(SiO4)3, is of variable composition and may
be red, yellow, brown, green or black. Andradite is the most is the most lustrous of
the Garnets and has several gemstone varieties.
Melanite: Lustrous, opaque black or very dark red in color, referred to as
"titanian andradite".
Demantoid: Olive-green to emerald-green in color, one of the most valuable
and rare stones in the gemological world.
Topazolite: Yellow to brownish-yellow in color and sometimes of
high enough quality to be cut into a faceted gemstone, it is rarer than demantoid.
Grossular
Grossular is the most varicolored of the Garnets It has the chemical formula
of Ca3Al2(SiO4)3 but the calcium may, in part, be replaced by ferrous iron and the
aluminium by ferric iron.
Hessonite: Orange to orange-brown, transparent variety of Grossular Garnet.
Hydrogrossular: garnet is the green, pink, grayish-white to bluish variety of
grossular.
Mali: is a yellow-green variety of grossular with a slight overlap in the grossularandradite series.
Uvarovite
Uvarovite is the rarest of the familiar Garnets, and is seldom used as a gem. Uvarovite is a calcium chromium garnet with the formula Ca3Cr2(SiO4)3. The color of
Uvarovite is a deep chrome-green, and Uvarovite is a unique Garnet being that it
only comes in one color.
ESTUDENTS: Ceiner Beleño, Luis Molina, Rafael Montero
