Montreal School of Gemology - cours-atelier

Coloured Stone Grading Workshop

Prerequisite courses : Gemmology 1, 2 & 3 (or equivalent work experience)

As the popularity of coloured gemstones continues to grow it is important for gem dealers, appraisers, and jewellers to understand the criteria used to determine the quality and value of coloured gems.

During EGM's two-day workshop students learn to grade coloured stones using colour quality, cut quality, and degree of clarity.  Understanding the impact these characteristics can have on value is important for anyone involved in the gem and jewellery business.

Colour perception is subjective requiring the gem and jewellery business to develop colour description systems based on hue, tone and saturation in an attempt to clarify colour definition and facilitate communication between buyers and sellers.  Students will learn to use three of these colour defining systems and acquire the necessary vocabulary to communicate with suppliers and customers when referring to coloured gems. EGM's vast collection of gems is used to demonstrate the possible range of colours for different gems and show students which colours are more desirable and valuable for each gem variety.

As with diamonds, the quality of a coloured gem's cut has a significant influence on the beauty, value and durability of the stone.  With observation of well-chosen examples students develop the ability to judge cut symmetry, proportions and light return.
Students leave this workshop armed with the necessary information to determine where a coloured gemstone's grade lies on the spectrum between 'commercial quality' and 'extra fine quality'.

The course includes an EGM coloured stone grading manual that will help students retain what they view in class and serve as a valuable reference for the future.


An EGM letter of completion will be issued to students who participate and pass a final practical test. EGM will also issue an official receipt for tax purposes.