Boron-oxygen compounds have considerable mineralogical and industrial importance. Many examples of isolated boron oxoanions containing one to six borons occur in mineral and synthetic berates. However, isolated boron oxoanions having more than six borons are rare, and there are no previous examples having nine borons. Described is the synthesis and structural characterization of crystalline guanidinium and imidazolium berates, [C(NH2)(3)][B9O12(OH)(6)] and [C3H5N2](3)-[B9O12(OH)(6)], containing the first examples of the isolated nonaborate anion [B9O12(OH)(6)](3-).