The Value of Coloured Gemstones

Ruby & Diamond Ring by Paul Wright Jewellery

Much is written about the value of diamonds and many are aware of the ‘Four C’s’ to look out for when buying them (Cut, Colour, Clarity and Carat weight). When assessing coloured gemstones, they too have four important C’s to consider. They are Colour, Colour, Colour and Colour! This is no exaggeration! In general the better and rarer the colour the less impact cutting, clarity and carat weight will have on the value of the gemstone. It really is all about its colour!

Naturally there is a high degree of subjectivity involved in making a colour assessment, especially as no system has yet been devised to measure the best ‘colour’ (in the way they have done with evaluating the colour of diamonds). How then do we determine the most desirable colour for a gemstone? Well the colours we see in gemstones are usually a combination of pure ‘spectral’ colours mixed with varying degrees of brown, white, black or grey. This results in the ‘tone’ or ‘shade’ of colour that describes a gemstone. For example if there is some white with the spectral red colour of a ruby then you will see a lighter tone or shade of red making it appear somewhat more pink in tone. The presence of black will make the ruby a darker shade of red. And so it can be seen that a huge range of ‘red’ colours are made possible in between. As a rule the most highly prized gemstone colours are those that are closer in colour to the pure ‘spectral’ colour without any tint or hue (although, in nature, one must accept there will always be some tint or hue present).

I should mention, at this point, that a gemstone’s colour can be significantly affected by the way it is cut. A good lapidary working with a fine gemstone, will be able to bring out the very best in the stones inherent beauty and thereby increase its desirability simply by knowing the best way to show off its vivid depth of colour. In general a gemstone that is too light or pale or, conversely, too dark will sell for less per carat weight.

The finest rubies from Burma are highly sought after because of their fine colour. This is because the colour of Burma rubies comes closest to pure red (although there will usually still be a slight bluish undertone). The tone will of course vary from very light to very dark. The most valuable will be those with a rich, deep colour in-between. It should also be mentioned that Burma rubies also tend to exhibit the best colour in all types of light i.e. in both daylight and in artificial lights. Unlike Thai rubies which can vary in hue and tone depending on the type of light source. Ceylon rubies are generally found with a paler tone and appear to be more pink than red. If the saturation of colour is too weak to be called ‘ruby’ (as technically ruby must be red), then it has become customary to call it a ‘pink sapphire’. This is because a sapphire and a ruby are in fact the same stone physically and chemically (both known as Corundum) but the red variety are always called ‘rubies’ and the blue variety are always called ‘sapphires’.

If we look at the colour of Emeralds, as another example, we find that some of the finest gems come from Colombia. This is because the green colour is an almost pure spectral green with just a faint hint of yellow or blue. Emeralds from other countries may be found with exceptionally good colour too but few can match those from Colombia. Those from Africa, and particularly from Zambia in more recent years, have a lovely green colour but tend to show a slightly more blue undertone than those from Colombia. However it should also be mentioned that the Zambian emeralds discovered today have far fewer inclusions than the Colombian ones and so are more vivid with greater saturation once cut. These compare very favourably with Colombian emeralds and have the added advantage that they are likely to cost less per carat weight. My own country of birth, Zimbabwe (or Rhodesia as it was then), is home to the Sandawana emerald mines, which were discovered in the late 1950’s. Sandawana emeralds are usually smaller in sizes and the larger carat weights, with a good colour, are quite rare and so highly sought after. Most emeralds from Sandawana have quite a dark Green to a slightly yellowish Green colour.

Once you start looking and comparing all the different colours of precious gemstones, you can train your eye into discerning what is the most desirable colour. In this way you can judge what is acceptable and what is objectionable. Very quickly you will learn to see the difference between the colour of a very fine gemstone and one that is less so. As a rule if you think the colour of one gemstone looks stunningly more valuable than another – it probably is!

Paul Wright Jewellery


Source: Jewellery & Gems by A. Matlins & 
A.C. Bonanno, 4th Edition 2009.
Photo by: StrangerThanKindness