The clarity scale

Contrary to diamonds, where a globally approved system is used worldwide, no agreement has been reached regarding the definition of the different grades of clarity in a coloured stone.

Following is the clarity scale which is in use by most of the professional trade members, and will be used in the course. For visualization purposes, each grade is presented with a relevant coloured sapphire gem image to demonstrate the appearance.

Loupe Clean

This clarity grade is given to a clear gemstone which is completely void of external and internal flaws. This must be certified by a trained evaluator who has studied the stone at 10x magnification (with the aid of a gemmological microscope), under optimal conditions for inspection.
Loupe Clean grade

Eye Clean

This clarity grade is awarded to a gemstone which contains very small inclusions, seen only when viewed with 10x magnifications. This definition includes internal inclusions and tiny external inclusions that are considered as flaws.
Eye Clean grade

Slight

This clarity grade is bestowed on a gemstone which contains small inclusions that are difficult to see with the unaided eye but seen clearly with a 10x magnification. This definition may include tiny bright crystals, small cracks, and a small light coloured cloud.
Slight grade

Moderate

This clarity grade is assigned to a gemstone that includes small inclusions, clearly visible when viewed with the unaided eye. This definition may include small dark or brightly reflected crystals, small cracks that are easily visible and distinguishable, and cloudy areas.
Moderate grade

Heavy

This clarity grade is allotted to a gemstone that includes noticeable flaws. In stones of this group, inclusions are clearly viewed with the unaided eye. Flaws exist in the form of rather large cracks, black spots, emphasized clouds, hard breaks and cleavages.
Heavy grade

Severe

This clarity grade is given to a gemstone that includes distinct noticeable flaws. Flaws can be viewed easily with the unaided eye. There is severe damage to the beauty in certain parts of the stone or partial damage in all parts of the stone. Inclusions may damage most of a stone's surface, and large breaks, cracks and grooves will limit its ability to withstand pressures of being set in jewellery over time. Stones of this grade are on the borderline of gem quality minerals.

As mentioned in the Colour Grades section, not all trade members use the above scale. Some traders replace the names of the grades above with the recognized diamond clarity grades (e.g. IF, VVS, VS, etc.) or use their own scale. However, their grading techniques remain the same.