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Garnet Gemstone Information

Garnet is a group of minerals with six main members:

Pyrope, Almandine, Spessartine, Grossular, Andradite and Uvarovite.

Please see separate entries.

All members of the group, except Uvarovite, may be cut as faceted stones or cabochons. Uvarovite is an emerald-green garnet that occurs in very small crystals, formed on a host rock called a druse. Although the individual crystals are too small to fashion, the druse itself can be cut and mounted into suitable jewellery settings.

Most garnets are a mixture of different varieties giving rise to a variation in their optical and physical properties. When that mixture is well defined i.e. there is an ample amount of each defining chemical element present. Then the garnet is defined as a separate member of the garnet group.

Garnets of this type include:

Malaya: Malaya garnets are a mixture of spessartine and pyrope, producing
orange to reddish-orange stones.

Colour Change: Colour Change Garnets are also a mixture of spessartine and pyrope.

but produce stones that appear green in sunlight and red in
incandescent light (filament light bulb).

Mali: Green to yellow stones, mainly grossular with some andradite.

Rhodolite:Rhodolite garnet is a mixture of almandine and pyrope producing

raspberry red to violet coloured stones.

Physical Properties

Stone type:
The Garnet Group.
Crystal System:
Cubic (isometric) commonly occurring as rhombic dodecahedron and icositetrahedron crystals.
Chemical Composition:
See individual entries.
Colour:
Garnets occur in all colours except blue. Colourless stones are called leuco garnets, a variety of grossular garnet.
Lustre:
See individual variety entries.
Pleochroism:
Absent.
Dispersion:
Medium.
Hardness:
See individual entries.
Toughness:
Fair to good.
Cleavage:
None.
Density in gm/cc:
See individual entries.
Double refraction:
None.
Refractive index:
See individual entries.

Common Treatments

Garnet topped doublets are produced, comprising a crown (upper section) of natural garnet and a pavilion (lower section) of glass. Almandine or pyrope garnet is normally used for the crown section. They can be easily identified by observing the following:

Viewing the stone from the side will show colour in the crown area only.

Close-up inspections will reveal a change in lustre at the join between the garnet and glass.

Bubbles are normally visible in the glass and/or the glue between the two layers.

Inclusions seen in the crown that are characteristic of garnet will not be seen in the pavilion.


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