Schiavinatoite

Schiavinatoite is a very rare borate mineral, and the niobium endmember of a solid solution formed with béhierite.
Schiavinatoite is classified as monoborate. It contains tetrahedral borate anion instead of planar BO₃ group, which is more common among minerals. Schiavinatoite is one of the most simple niobium minerals. Both minerals possess zircon-type structure and occur in pegmatites. Schiavinatoite and nioboholtite are minerals with essential niobium and boron.

Occurrence and association

Schiavinatoite was detected in miaroles of a pegmatite at Antsongombato, Madagascar. It coexists with an apatite-group mineral, béhierite, danburite, elbaite–liddicoatite, feldspar, pollucite, quartz, rhodizite, and spodumene.

Crystal structure

The main facts about schiavinatoite's structure:

isostructural with zircon
niobium coordination number of 8
tetrahedrally-coordinated boron
chains of edge-sharing BO₄ and NbO₈ polyhedra, parallel to
edge-sharing dodecahedra link the chains