Understanding Pearl Colour
When most people think of pearls, they picture a classic white strand of perfectly round gems. While this is the classic image for many people, pearls actually come in a wide range of natural colours. Depending on the oyster species, and many other factors including the inserted mantle tissue piece and the oyster’s environment, both freshwater and saltwater pearls have very distinctive natural colours.
There’re three aspects to the colour of a pearl, namely bodycolour, overtone and orient. Bodycolour is the overall colour when you look at a pearl. It can be white, cream, yellow, black, blue and etc. The overtone is the translucent colour over its surface. When present, it’s usually visible over a large part of the gem body. Orient occurs when there is rainbow iridescence appearing over the pearl surface.
Colour is one of the seven value factors that determine how valuable a pearl is. Generally speaking, natural colours are always more valuable than artificially treated colours when other value factors are equal. Pearls with overtone and orient are usually more precious than those without.
Typical Tahitian Pearl Colour
Tahitian pearls, or black pearls, don’t just come in the colours of black and grey. In fact, they have an exotic array of deep shades including aubergine, peacock, black, brown, purple and many more in between. Their overtone can be pink, green and blue.
Genuine South Sea Pearl Colour
South Sea pearls, indigenous to the warm waters of northern Australia, Indonesia, the Philippines and Burma, have a natural bodycolour of white, cream, champagne, and golden. Although the silver-lipped species mainly yield white to silver South Sea pearls, and the gold-lipped variety produces mostly yellow to golden coloured gems, both types can have either colour. In addition to their bodycolour, South Sea pearls can also display various overtones including pink, green and blue.
Freshwater Natural Pearl Colour
Grown in lakes, ponds and rivers, freshwater pearls generally have a bodycolour of white, cream, yellow, orange, pink or purple. These subtle pastel colours are unique to the freshwater variety. In addition, they often have an overtone of pink, blue and green, and can sometimes display beautiful orient, especially in the case of irregular baroque shapes. Colour terms such as “apricot”, “peach”, “lavender” are often used to vividly describe these gems.
Natural Akoya Pearl Colour
Akoya pearls, the first cultured pearl production pioneered by Mikimoto Kōkichi, range from white, cream to yellow. They often exhibit a delicate pink or green overtone but do not usually show orient.
Artificially Coloured Pearls
By understanding natural colours in different pearl types, you can easily spot those pearls that are artificially dyed. For example, black or golden freshwater pearls are the result of colour treatments to imitate the exotic look of the Tahitian and South Sea type. The value of those pearls, in general, will always be lower than the Tahitian or South Sea variety when all the other value factors are equal.
Bleaching and Pinking
It is also important to note that virtually all Akoyas and most freshwater pearls are bleached to achieve the whiter colour during processing despite the fact they naturally occur in white. Pinking, a technique that uses a weak red dye to tint Akoya pink, is also commonly used in Japan and China. These are universal industry-wide practice that forms part of the processing procedures.