A-Z of Gemstones: G

Posted on the 14th November 2016

A-Z of Gemstones: G: Garnet

GARNET

Garnet is a wide group of closely related mineral species with many varieties.

Garnets range from red, brownish red, purplish red, orange, yellow to green.

The most valuable varieties of garnets are tsavorites and demantoid garnets, both of which are green.

Another desirable variety of garnet is the purplish red Rhodolite.

Some garnets display phenomena such as colour-change and asterism; the former refers to stones that change colour when seen under a daylight equivalent light source and under incandescent lighting and the latter phenomenon when cabochon-cut stones have a whitish star on top of the dome.

Depending on the transparency of the stone which can be anything between transparent to semi-translucent, garnets are cut into faceted gems, cabochons and beads.

Garnets have a vitreous to sub-adamantine lustre; they rates 6.5-7.5 on the Mohs scale which makes them suitable for jewellery that has secure settings to protect the stones from wear.

The main sources of garnets are: Brazil, Tanzania, Kenya, Madagascar, Russia, Sri Lanka, Brazil and India.

Garnets are not usually treated and they have not yet been synthetically grown.

Materials that are most commonly used to imitate garnets are: CZ , lab-made YAG (yitrium aluminium garnet) , glass and plastic.

Garnet is the January birthstone.