Synthetic B-rich olenite: Correlations of single-crystal structural data

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(Na_(0.7)□_(0.3))^Y(Al_(2.5)Li_(0.4)Fe^(2+)_(0.1))^ZAl_6(BO_3)_3[Si_(5.2)B_(0.5)Al_(0.3)O_(18)]^V[(OH)_(2.9)O_(0.1)]^W[O_(0.9)(OH)_(0.1)], with α = 15.765(1), c = 7.083(1) Å, ^X(Na_(0.7)□_(0.3)) ^Y(Al_(2.5)Li_(0.5))^ZAl_6(BO_3)_3[Si_(4.8)B_(0.9)Al_(0.3)O_(18)]^V(OH)_3^W[(OH)_(0.5)O_(0.5)], with α = 15.746(1), c = 7.075(1) Å, and ^X(Na_(0.6)Ca_(0.1)□_(0.3))^Y(Al_(2.3)Li_(0.5)Fe_(0.2))^ZAl_6(BO_3)_3[Si_(4.7)B_(1.2)Al_(0.2)O_(18)]^V(OH)_3^W[(OH)_(0.9)O_(0.1)], with α = 15.723(1), c = 7.068(1) Å. The small 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 (r^2 = 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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