Garnet
Characteristics
- Habit - cubic
- Form - rhombic dodecahedron or icositetrahedron
- Hardness - 6.5 to 7.5 (hard)
- Cleavage - none
- Fracture - conchoidal, brittle
- Streak - white
- Lustre - vitreous, bright
- Colour - black, brown, red to purplish-red, greens
Garnet samples from the day workshop.
Introduction
January birthstone. Transparent to translucent. Comes from Latin 'granatum' meaning pomegranate, the crystal thought to resemble the red of the seeds.
Lore: would gladden the heart and dispel sorrow. Popular in Greece during the time of Alex. the Great when it signified fertility. Also represented friendship. Healing & protective properties (apotropaic). In the Middle Ages it was worn by knights to protect them from injury.
Includes most common - pyrope (red and purplish-red), almandine (red to black). Also spessartine (orange to brown), hessonite (orange to brown), demantoid (rare green), tsavorite (rare green) and grossular (pink to red, green). The rare greens are highly prized eg: from Russia or Tanzania.
The quality of the material (as with other stones) will determine if it is cut as a faceted gemstone or cabochons. It is not pleochroic and will only show one colour under the dichroscope. Good quality = good colour, transparent, not too dark.
Varieties
Demantoid
Best known. Discovered in 1868 in Russia. The best are deep green with high dispersion (fire). Often has radiating fibrous inclusions resembling horsetails - this indicates it may be Russian in origin. Few times an inclusion will add value.
Although Mohs' 6.5-7.5 this one should be treated with care.
Tsavorite
Discovered in 1968 and now popular due to its clarity and lively colour.
Can appear yellowish-green and show variations. When the colour goes to that of a fine emerald it can be highly valued, esp. if free from inclusions.
Almandine
Found in metamorphic rock. Multifaceted, with complex crystals of 48 faces. Harder than steel so used as abrasives in grinding wheels, sandpaper and saws. Is Connecticut's state mineral
Arab Roots of Gemolgy
Some elements from 'Arab roots of gemolgy: Ahmad ibn Yusuf Al Tifaschi's Best Thoughts on the Best of Stones' (c.1240) trans. Samar Najm Abul Huda. The Scarecrow Press, London, 1998.
Four varities:
- mazenbi - light red colour, clear and transparent, similar to a good ruby, most expensive
- ratb - strong red colour, half price of mazenbi
- azbazashtt - light yellow, has the property of stopping nose bleeds, half price of ratb
- bahandji - reddish black, slightly reddish shade coupled with a tinge of blue, half price of azbazashtt
Value is a quarter that of spinels or less.
