Laboratories for Gemstones Grading

Laboratories for Gemstones Grading

There are a number of laboratories which grade and provide reports on gemstones.

- International Gemological Institute (IGI), independent laboratory for grading and evaluation of diamonds, jewellery and colored stones.

- Gemological Institute of America (GIA), the main provider of education services and diamond grading reports.

- Hoge Raad voor Diamant (HRD Antwerp), The Diamond High Council, Belgium is one of Europe's oldest laboratories.

- American Gemological Society (AGS) is not as widely recognized nor as old as the GIA.

- American Gem Trade Laboratory which is part of the American Gem Trade Association (AGTA), a trade organization of jewelers and dealers of colored stones.

- American Gemological Laboratories (AGL)

- European Gemological Laboratory (EGL)

- Gemmological Association of All Japan (GAAJ-ZENHOKYO), Zenhokyo, Japan, active in gemological research.

- Gemmological Institute of Thailand (GIT) is closely related to Chulalongkorn University

- Gemmology Institute of Southern Africa, Africa's premium gem laboratory.

- Asian Institute of Gemmological Sciences (AIGS), the oldest gemological institute in South East Asia, involved in gemological education and gem testing.

- Swiss Gemmological Institute (SSEF), focusing on colored gemstones and the identification of natural pearls.

- Gübelin Gem Lab, the traditional Swiss lab.

Manufacturing Process of Gemstones and Cabochons

Gemstone - A precious or semiprecious stone that may be used as a jewel when cut and polished.

Cabochon: a highly polished gem that is cut convexly but without facets

Grading of Gem Stones

Gemstone and stone beads grading is less formal than gemstone grading as a whole. Still there are some generally accepted rules that determine which grade is assigned to a stand. Grade is assigned based on a letter with A being best and "D" being worst. Note that "D" might be just what you want for a specific project, so don't dismiss them as worthless. Sometimes you might see gem grades of A A A and A A. Those are real gem grades with A A A being near perfect. It's rare for such good quality stones to be cut into beads. They are worth more as faceted gems. The overall quality of the stones in the strand is usually derived from a combination of the classic gemstone qualities of color, cut and clarity. I will include more about grading in the next article but as far as I think you may have some idea about gemstones.

Manufacturing process:

Raw Material:

There are various kinds of gemstones like ruby, emerald, sapphire, amethyst, citrine, aquamarine and many more. These gemstones are found in different parts of the world and are imported by the suppliers and exporters direct from the mines as rough stones. These rough stones work as raw material for further processing.

Shape and size:

These rough edged stones are further decided to convert into shapes like oval, round, square, faceted, chips, smooth etc. and size as per the requirement.

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Magical Properties of Gemstone Beads

The qualities of gemstone beads are beauty, rarity and durability. The beauty of a gem depends on its properties that how it looks or visible, its features include shine, fire and color of a gemstone bead. The durability of the gemstone beads depend on hardness and resistance to cleavage or breakage. If we look at the physical properties of gems, some resembles each other and some are quite different.

These can be recognized by it crystal properties, index of refraction of light, hardness, presence or absence of cleavage, type of fracture (concordat, even, or uneven) in stones without cleavage, specific gravity, color, streak (color of the powder as determined by rubbing it over white, unglazed porcelain), luster (appearance of the surface in reflected light – adamantine, vitreous, resinous, greasy, silky, or pearly), and transparency. Minor properties that serve to identify some stones are chiromancy (changeable luster or color under undulating light), opalescence, asterism (star like sparkling), and play of color, fluorescence, phosphorescence, iridescence, and electrical properties.

The unit of weight used for gemstones is the metric carat; one carat equals 200 mg.


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