CLARITY
When it comes to grading a diamond, you don’t expect to see any inclusions with the naked eye. Most expect to find the same characteristics in a coloured gemstone as you would in diamonds. When it comes to the clarity of a coloured gemstone it is almost unheard of to find a stone that is considered flawless. Colour itself results from the presence of trace elements so from the very start you are going to have inclusions. As a result, coloured stones are held to a different clarity standard than diamonds. With diamonds, there is a very precise grading system. With coloured gemstones, there is no universally accepted grading system and each category of a gemstone is different in terms of what is acceptable. In general, coloured gems fall into three broad categories.
- Gems in category one form under the gentlest of geologic conditions and you don’t expect to see something with your naked eye. Some examples of category one are; Aquamarine, Morganites, Amethyst, Citrine and Tanzanite.
- Gems in category two from under more difficult geologic conditions. It is not at all uncommon to see minor things with the naked eye. Some examples of category two are; Ruby, Sapphire, Garnet, Iolite Peridot, Alexandrite
- Gems in category three for under the most violent geologic conditions therefore they are more prone to have cracks and other features readily visible to the naked eye. Some examples of category three are Emerald, Beryl and Tourmaline
An emerald is the classic example of a gemstone that’s formed under violent geological conditions. So, if one sees a large deep green emerald and they don’t see anything with the naked eye the first thing people wonder is if it is real because we are so accustomed to the fact emeralds do have inclusions that are usually visible.
Typically, the more inclusions in a stone the lower the price. But these tiny imperfections are also what gives each individual gem its own distinct personality.
COLOUR
The colour of a gemstone is given by three parameters. The hue, the impression of colour we get. The tone, How light or dark that colour may be and saturation, how vivid or pure the colour is in the gemstone. The colour of a gemstone is formed from trace elements found in the stone when it's being formed. It is common to have uneven colouring in one single gemstone. Some gemstones are more prone to having colourless zones like sapphires and amethysts. Some gems can also combine more than one distinct colour. Called multi colouring the phenomenon is common in many different varieties of tourmaline with some examples showing as many as 15 different colours.
CUT
The cut of a coloured gemstone is often determined by the gems crystal structure. For example, an emerald has a long crystal structure so typically it is cut into a square or rectangular format. Where sapphire and rubies crystal structure is different they typically cut it into cushion cut. The geometry of the rough isn’t the only thing that determines the cut of the gem. How a gem is cut often enhances a gems other defining characteristics particularly colour. The skilled gem cutter considers everything when cutting a stone to bring out the best in each piece.