I have received data from the GIA on the tourmaline they ran on their laser ablation equipment during my latest trip to the west coast. I have some questions, but one thing is obvious. There is a lot more tourmaline with measurable amounts of lead than I thought. When I first sumitted the reverse color changers (Laurellite) to the GIA for testing, they felt the lead they found was possibly from contamination during polishing. It was later determined that many cuprian tourmaline have measurable lead. Well now I have found some high levels of lead in non cuprian tourmaline. One non cuprian purple, that is probably from Madagascar, had approximately 17,000 ppm which is higher than a colorless tourmaline that I thought exceptional. (The achroite was tested at the Washington University of St Louis and its lead content was confirmed by GIA testing).
Both the purple and the colorless do not have significant amounts of copper and are Liddicoatites. I do not know if having high levels of calcium has any impact on the levels of lead, but I feel they probably both came from Madacascar.
Ah the complexity of tourmaline.
Bruce
