Abstract

Synthetic Al- and B-rich tourmaline crystals described by London (2011) were characterized further by SIMS and new EMP analyses. These tourmalines are the first synthetic B-rich olenites characterized by single-crystal X-ray diffraction, because they are significantly larger than synthetic samples produced in the past. The average final formulas are X(Na0.70.3)Y(Al2.5Li0.4Fe2+0.1)ZAl6(BO3)3[Si5.2B0.5Al0.3O18]V[(OH)2.9O0.1]W[O0.9(OH)0.1], with a = 15.765(1), c = 7.083(1) Å, X(Na0.70.3) Y(Al2.5Li0.5)ZAl6(BO3)3[Si4.8B0.9Al0.3O18]V(OH)3W[(OH)0.5O0.5], with a = 15.746(1), c = 7.075(1) Å, and X(Na0.6Ca0.10.3)Y(Al2.3Li0.5Fe0.2)ZAl6(BO3)3[Si4.7B1.2Al0.2O18]V(OH)3W[(OH)0.9O0.1], with a = 15.723(1), c = 7.068(1) Å. The small <T-O> distances, down to 1.599 Å, reflect relatively high amounts of [4]B (up to ~1.2 apfu; refinements with R = ~2%). All these samples also contain significant amounts of [4]Al (~0.2 apfu). A pronounced negative correlation (r2 = 1.00; only three data points) between temperature during crystal growth (at a constant pressure) and [4]B (from refinement) in these synthetic olenites was found.

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