Blue surprise: apatite 
and not Paraiba tourmaline

First published in Facette 28 (May 2023)

Last summer, the SSEF received a series of nine small blue cabochons ranging in weight from 0.4 to 1.5 ct. The client assumed that these stones were Paraiba tourmalines from a very early production of the Sao José da Batahla mine in the state of Paraiba in Brazil, as they were safeguarded for several decades by a jeweller. Already doubtful in appearance, these “Paraiba” stones were quickly identified as apatite, well-known to occur in Paraiba-like colours, specifically after they are subjected to heat treatment. Based on the presence of reddish iron-oxide in some hollow channels, it is highly probable that these apatite cabochons were heated. In addition, the fissures (maybe partly induced by the heating process) in these rather included cabochons showed indications of clarity modification by minor to moderate fissure filling. The result was not so thrilling for the client, but at least this Paraiba-mystery could be solved.

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