Gemology

The committee emerged as a distinct branch of NAG (named the Gemmological Association) in 1931, shortly after the incorporation of the Gemological Institute of America (GIA).

The first US graduate of Gem-A's diploma course, in 1929, was Robert Shipley, who then established both the Gemological Institute of America and the American Gem Society.

The first gemological laboratory serving the jewelry trade was established in London in 1925, prompted by the influx of the newly developed "cultured pearl" and advances in the synthesis of rubies and sapphires.

Gemstones are basically categorized based on their crystal structure, specific gravity, refractive index, and other optical properties, such as pleochroism.

When the gemstones are in a rough state, the gemologist studies the external structure; the host rock and mineral association; and natural and polished color.

Initially, the stone is identified by its color, refractive index, optical character, specific gravity, and examination of internal characteristics under magnification.

Gemologists use a variety of tools and equipment which allow for the accurate tests to be performed in order to identify a gemstone by its specific characteristics and properties.

The powdered gem mineral is then melted (or a metallic mixture directly burned in an oxygen flame) the residue of which then drips through a furnace onto a boule.

Likewise, natural stones, particularly beryl minerals, show small flaws – short planar cracks where the direction of the crystalline orientation in the gem abruptly changes.

The natural formation of gemstones tends to layer the minerals in regular crystalline sheets, whereas many synthetically produced gems have an amorphous structure, like glass.