Introduction

Rubies have an almost other worldly quality that has beguiled and delighted humanity throughout the ages. Today, fine-quality rubies are commanding the highest price per carat of any coloured gemstone, often breaking auction records.

Gemfields Mozambican rubies from Montepuez are over 500 million years old and the deposit is believed to be the largest known in the world. The rubies are often low in iron content, which is a good characteristic as too much iron can darken and dampen the fluorescence of the ruby.

In addition to the ‘Four Cs’, two additional ‘Cs’ play a pivotal role when considering coloured gemstones, Certification and Character.

Colour

Colour can have a dramatic impact on the value, making it a defining gem characteristic. A gemstones colour is described by reference to hue, tone and saturation. Hue describes the accuracy of the principal colour and the extent to which secondary colours are present. The strength of the secondary colour typically detracts from the intensity of the primary colour.

Clarity

Clarity typically ranks after colour when evaluating coloured gemstones. It describes the extent to which a gemstone contains inclusions and fractures and their position within the gem. The fewer the inclusions, the better, as this enhances transparency, brilliance and overall look. Inclusions in a gemstone are a natural part of the gem and give coloured gemstones their unique character.

Cut

Cut describes the shape into which the rough gemstone has been cut and polished in a lapidary. Cut is typically divided into faceted gems (gems with geometrically shaped flat faces) and non-faceted gems (gems with rounded surfaces, generally called cabochons). Value is enhanced when a gemstone is well proportioned and symmetrical, has been well polished and possesses a good lustre.

Carat

Carat gemstones are typically sold by the carat, a unit of weight not size. The word carat comes from the ‘carob’ seed, the original unit of measurement of gem traders.

Certification

Certification lies at the heart of a buyer’s confidence in, and credibility behind, any gemstone. A report from a licensed gemmological laboratory will confirm the characteristics and qualities of your gemstone, including not only its colour, clarity, weight and dimensions but also its country of origin (where tested) and the presence, if any, of treatments used to enhance the appearance of the gemstone.

Character

Character is the very essence of why coloured gemstones are different to diamonds. The characteristics and value of most diamonds can be well described by four objective measures (being the ‘Four Cs’). This is not the case with coloured gemstones. Like people no two coloured gemstones are identical. Each has its own uniqueness and character.