Yellow Danburite from Namalulu, Tanzania, and Myanmar: Origin of Colour and Its Stability
A rough yellow danburite from Namalulu, Tanzania, (a) was heated to 500° C for four hours, resulting in a complete loss of colour, and the sample remained colorless after further heating to 950° C for 24 hours (b). For another test, one bead of Namalulu danburite was kept as a reference sample, while another bead was exposed to a tensor lamp for eight hours (c, left and right samples, respectively). After three hours, the bead exposed to the lamp darkened and became more brownish.
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Photos by Bilal Mahmood (a, b) and C. P. Smith (c).
