Wednesday, 27 February 2013

Introduction Spessartite Garnet Gemstone

Silicate of manganese and aluminum belonging to the garnet family. It is named after the Spessart region of Bavaria (West Germany), although only minor deposits are found there.

Crystal system

Spessartine has the typical crystal form of garnets, usually occurring as isolated, well formed, rhombic dodecahedral crystals. The color is orange-pink, an angered, or brownish yellow. It may be semiopaque or transparent. Transparent crystals are highly lustrous it has no cleavage. The transparent specimens are used a gems.

Physical properties
It has a hardness of 6.5-7.5. The density of gem-quality stones varies from 4.12 to 4.21 g/cm3. The refractive index can vary from about 1.79k 1.81.

Spessartine occurs in low-grade metamorphic rocks, but is uncommon.

Crystals of grossular garnet
It is mainly found in the United States Virginia and California), Mexico, and Madagascar, but also 1.80 West Germany and Italy (Piedmont and Val d'Aosta).

The gem variety of spessartine garnet is uncommon. It tends to be midway between spessartine and Alma, composition.

The "aurora red," orange-red or pink color is typical. It has good transparency and considerable luster. It is normally given a mixed, round, cut. The weight does not normally exceed a few Gems of about 10 carats are extremely rare and us an atypical, rather dark, unattractive color.

Distinctive features
The color, single refraction, luster are useful means of identification, but the p properties have to be measured to distinguish it, stance, from some hessonite garnets. Examination absorption spectrum can be very useful; where clearly visible, which is not always the case, it is distinctive.

Spessartine Garnet
Spessartine is extracted from the gem gravels of Sri Lanka and Burma. It is also found in the States (Virginia and California), Brazil, and Madagascar.

Its value is a bit higher than pyrope and almandine, about the same as rhodolite. Ills not often found the market.

Simulants and synthetics
It is neither imitated not produced synthetically.

Writer – Curzio Cipriani and Alessandro Borelli

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