We all know what colours gemstones should be … or at least, we think we do. But what colour is it really? It all depends on the light. The ambient lighting can change the colour of your stone you’re looking at.
The pictures below show a stone that could either be a pink sapphire … or a ruby. It changes depending on the type of lighting under which you’re viewing the stone.
So what colour is your gemstone? Is your pinkish reddish stone a ruby – or a pink sapphire? Is your tanzanite bluish violet – or violet blue?
Consider an excellent final-grade-quality 1.00ct natural ruby. The wholesale price is $8100 per carat. The same quality pink sapphire will wholesale for $5 200 per carat. That’s a pretty substantial difference! Under daylight it is a pink sapphire … but under tungsten lighting, it would be a ruby. In other words, a single light bulb could make a $2 900 (R43 500!) difference in the final price.
As you can see, the correct lighting is vital for consistent colour grading. Modern diamond grading lights deliver the equivalent ambient light to North facing morning daylight in the Northern hemisphere. Using these lights, we can ensure accurate, reliable gemstone grading.
My mentor, Ian Campbell, standardised the colour temperature for grading pearls and coloured stones in 1982. The standard he set was around 4500o Kelvin. Following in his footsteps, I am in the process of making a suitable light source for you to use to check the colour of your gemstones under the correct colour temperature. Using these new lights, you will have the tools you need to make informed decisions when buying or selling gemstones, or doing jewellery valuations.
As soon as the lights have been completed and tested, and are available for purchase, I’ll let you know. In the meantime, contact me for pre-orders (or any questions you’d like answered). Call me on 021 761 1746. Or email jeremy@gemlab.co.za.
