What is "aspedamite"

Aspedamite is a very rare mineral, one of two natural heteropolyniobates. Its chemical formula (one of the possible formulas) is complex and shows the presence of essential vacancies: [](FeFe)Nb(ThNbFeTiO)(HO)(OH). Its structure (isometric, space group Im3) is the same as of the second known heteropolyniobate - menezesite. Aspedamite is somewhat similar to another mineral from Norway, peterandresenite, which is a hexaniobate.