This is a particularly interesting kind of tourmaline. It is fine traces of magnesium that are responsible for the electrifying yellow colour. Since not all the raw crystals actually show that radiant yellow when they are found, some of the stones first have to submit to a period spent in the oven at approximately 700 degrees Celsius. Without this treatment, the colour would have a slight brownish tinge. The treatment only brings about the desired result because tourmalines typically display different colours and different colour intensities in different directions. By heat treatment, the tourmaline's second colour, in this case a light brown, is also transformed into the coveted radiant yellow. This is a kind of treatment customarily undertaken with many gemstones, the result of which is irreversible. Large yellow tourmalines are rare in Malawi too, the more so in view of the fact that only some 10 per cent of the yield is actually of gemstone quality at all. When cut, more than 95 per cent of the stones weigh less than one carat. However, they have wonderful wearing qualities, for like all tourmalines the canary-yellow beauties from Malawi have a good hardness of 7 to 7.5 on the Mohs scale.
Yellow Tourmaline
This is a particularly interesting kind of tourmaline. It is fine traces of magnesium that are responsible for the electrifying yellow colour. Since not all the raw crystals actually show that radiant yellow when they are found, some of the stones first have to submit to a period spent in the oven at approximately 700 degrees Celsius. Without this treatment, the colour would have a slight brownish tinge. The treatment only brings about the desired result because tourmalines typically display different colours and different colour intensities in different directions. By heat treatment, the tourmaline's second colour, in this case a light brown, is also transformed into the coveted radiant yellow. This is a kind of treatment customarily undertaken with many gemstones, the result of which is irreversible. Large yellow tourmalines are rare in Malawi too, the more so in view of the fact that only some 10 per cent of the yield is actually of gemstone quality at all. When cut, more than 95 per cent of the stones weigh less than one carat. However, they have wonderful wearing qualities, for like all tourmalines the canary-yellow beauties from Malawi have a good hardness of 7 to 7.5 on the Mohs scale.
Subscribe to:
Post Comments (Atom)
Magnesium can not color tourmaline. It is not a transition element nor does it form associations with other elements to form color centers. This gem is probably color by high levels of manganese.
ReplyDelete