Garnet

Colour and varieties

Gem garnets occur in various colours including red, orange yellow and green.
Rarely four-and six-rayed star stones can occur.
Colour-change garnet which appears bluish-green in daylight to purplish-red in incandescent light.

Gem garnets are transparent to translucent and have a bright vitreous lustre. The name ‘garnet’ refers to a group of minerals related in composition and crystal structure. As with other gemstones, quality determines whether garnets are faceted or cut as cabochons. Garnets have a mdium to high dispersion often masked by their body colours.

All garnets have the sme general chemical formula X3Y2(SiO4)3. The group is split into two isomorphous series:

In one series X may be magnesium (Mg), iron (Fe) or manganese (Mn), while Y is always aluminium (Al).
In the other series, X is always calcium (Ca), while Y may be chromium (Cr), aluminium (Al) or iron (Fe).

Occurrence and crystal habit

Garnet occurs as crystals in metamorphic and igneous rocks, as rolled pebbles in alluvial deposits and broken fragments. Nearly all crystals are of rhombic dodecahedron or icositetrahedron form. Oriented fibrous inclusions may be seen.
Garnet is the birthstone for January. The name ‘garnet’ is derived from the Latin name granatum – meaning pomegranate because of the strong resemblance of the red crystals to the seeds of a pomegranate.
During the great biblical flood, Noah was said to have used the red glow from a garnet to guide his way through the darkness. Garnet is often associated with illumination and bringing light into the dark. For example, garnet jewellery was buried with Vikings to help light their way on the journey to Valhalla. Garnet is also said to have great healing properties; it could strengthen the heart and cure melancholy if ground up and swallowed. In the middle ages knights would place them on their shields to prevent injury.

General Care

Garnets are usually very durable, except for demantoid which is the softest of all garnets; more care is needed when handling this material.

Workshop Care

Heat
Thermal shock as abrupt changes of temperature may cause fracturing
Steam cleaners
The jewellers torch.