Ammonioborite: New Borate Polyion and Its Structure

Science  29 Jan 1971:
Vol. 171, Issue 3969, pp. 377-379
DOI: 10.1126/science.171.3969.377


The mineral ammonioborite is monoclinic with unit cell dimensions (in angstroms): a = 25.27, b = 9.65, and c = 11.56; β = 94°17', and the space group is C 2/c. Analysis of the crystal structure revealed the crystallo-chemical formula (NH4)3B15O20(OH)8·4H2O, with four such formula units in the unit cell. The basic structural unit is the double ring consisting of one BO4 tetrahedron and four BO3 triangles: in ammonioborite three of these units are connected to give trimeric ions [B15O20(OH)8]3-.