Abstract
An examination of synthetic crystalline material by single crystal X-ray diffractometry reveals a unit-cell dimension that was previously ascribed to tincalconite. However, the best fit to the reflection data obtained at 291(2) K is obtained with composition Na6[B4O5(OH)4)]3·8H2O. This formula is different from the Na2[B4O5(OH)4)]·3H2O previously assigned to tincalconite from an earlier crystallographic study. Additionally, our model fits best with non-crystallographic measurements and agrees with the analysis from a more recent low temperature crystallographic analysis. Tincalconite is best formulated as Na6[B4O5(OH)4)]3·8H2O. It is trigonal, R32, a = 11.1402 (11), c = 21.207 (3) Å, Z = 3, R = 0.020 for 512 Fo > 4σ (Fo) and 0.021 for all 529 data at 291(2) K.
© 2015 by Walter de Gruyter Berlin/Boston
