Grading coloured stones…a perilous path

Shoppers love diamonds that have laboratory grading reports. A report gives them a feeling of confidence while making a buying decision, especially when thousands of dollars are at stake based on a slight difference of grades. A diamond that is graded by a major lab is often much easier to sell at a higher price.

Diamond reports can also be the kiss of death for some stones, thanks to the internet. Online diamond forums are training buyers to focus on specifications instead of beauty. They hit the stores with a list of parameters that must be met on paper before they will consider looking at a stone. Diamonds below I or J in colour, I1 in clarity or that show fluorescence are usually dismissed immediately. There are many diamonds that absolutely stunning that do not fall within the acceptable range and never get a chance to find a home. They end up as price-point goods instead of being sold for beauty.

Coloured gemstones, for the most part, have escaped the trap of grading reports. Coloured stone reports from the major labs are focused more on establishing identity and detecting treatments. Clarity and colour are typically mentioned only as part of a description and not as a grading element. This is true with coloured diamonds as well where the concern is with origin of colour and not grading.


Colour does not lend itself willingly to grading.  There are too many obstacles to overcome to have a viable grading system.  There is no such thing as a consistent light source or viewing environment.  Even lamps of the same type change with age.   We have yet to get past the difficulties of accurately and consistently describing and communicating basic colours.  Gem eWizard, Gemdialogue, and many others are making valiant attempts but so far we don’t have any system that we can all agree on or get consistent results and I doubt we ever will.

Our eyes are the problem.  We all perceive and process colour differently.  Slight variations in sensitivity or colour blindness makes each of us see slightly different colours.  We aren’t even consistent with ourselves because our health, diet and medications can have a significant effect on our colour vision.   If we can’t see colour the same each time, we certainly will find it impossible to communicate that colour to another individual.

Technical issues aside, if grading reports become as prevalent for coloured gems as they are for diamonds; we are in trouble.   Online gurus will start touting preferred attributes, just as they do with diamonds, and many beautiful stones will perceived as inferior because they do not meet the standards imposed by online peer pressure.

Colour preference is an emotional response.  We need to allow our customers the freedom to follow their heart without the interference of someone else’s opinion.

Leave a Reply