There are many gemstones and gemstone groups most of which were discovered centuries ago but some, such as Lothruin were discovered recently.

 The grading of coloured Gemstones follows the techniques used for grading diamonds by evaluating colour, clarity, cut and carat weight, although this is pretty much where the similarities in the grading standards end. Unlike diamonds, when evaluating a coloured gemstone, a decision is more likely to be based on the actual colour.  This can be further characterised to the hue, saturation and tone of the colour present within the Gemstone.

The hue of a Gemstone is possibly the most well known, this relates to the Gemstones physical colour.

The saturation relates to the vividness of the colour or hue of the Gemstone.

This is the term used to describe the lightness or darkness of the colour (Hue).

A skilled Gemmologist, the person who values Gemstones, uses their skill and judgement to decide what the actual hue of the Gemstone actually is. This is not an exact science and as such a Gemmologist must draw upon years of experience and knowledge to ensure that the hue they describe the Gemstone as is correct when comparing the Gemstone to specially created tables that help the gemmologist describe the colour accurately. The description of both the saturation and tone of the colour is decided upon in a similar way.

As with most natural occurring materials Gemstones also include other minerals within, these “inclusions” can either enhance a Gemstone or detract from their overall beauty, although this facet of the valuation process is easier than colour grading section, it tends to be more tangible as the inclusions are present to view, it still takes skill and expensive equipment to ensure the Gemstone is described correctly.

As with Diamonds a coloured Gemstones cut is vitally important, when the cutter initially takes possession of the rough or uncut Gemstone he must decide how best to cut the stone to remove undesirable colour fluctuations and inclusions but to retain the highest carat weight and retain a good overall symmetry, it is the Gemmologist who decides if the cutter has done this correctly. A badly cut stone that shows many inclusions or a colour fluctuation and has a bad symmetrical cut is worth far less than one whose proportions and colour are viewed to be better.