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The draining of a colour in a gemstone due to lighting conditions is known as bleeding.

Not a nice thought, but this is the best way I can think of describing it: you know how you tend to lose colour when you badly cut yourself? Well, that is what we mean when we say that a gemstone bleeds. Now of course a gemstone cannot bleed in the same sense, but if you view a gem under one light source and then under another some gems will suffer the same effect. Bleeding is not be confused with the effect known as “colour change” where a totally different hue is seen, it’s more to do with the draining of colour.

For example most Sapphires when worn in doors under incandescent light can often lack sparkle; their tone seems to diminish and the gem almost fades, but once taken back outside into natural sunlight their tone is instantly revitalised. Not all Sapphires bleed in the same way and the level of their bleeding depends on their chemical composition.

Garnets and Tourmalines are also prone to bleeding and it is for this reason that at Gems  TV, we first show our jewellery under studio incandescent lighting so that their “bled colour” can be seen and then, when practical, we will show the piece in a light box which simulates daylight so that the gem’s true vivid colour can be revealed.

Two gems that bleed more than most I have seen are Pink Tourmaline and Rubellite. Their colour becomes more brownish under incandescent lighting and they appear to lose a lot of transparency. Although this is not strictly bleeding, it is the nearest gemmological term I could find to describe its change.

Rhodolite Garnet, especially the famed Naktamunda Rhodolite, will appear a muddy colour under candle light or indoor lighting, yet turn on your fluorescent lamp, or hold them to your window under the midday sun and their colour is described by many gem experts as the finest natural coloured gemstone on the planet. When my good friend Manuj introduced me to the gem I could not see what all the fuss was about, but when he then led me to his office window, and opened the blind, I was amazed at the transformation in the gem; once it had stopped bleeding it was truly stunning.

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