Nenadkevichite

Nenadkevichite is a rare silicate mineral containing niobium with formula: (Na,Ca)(Nb,Ti)Si₂O₇·2H₂O. It forms brown to yellow to rose colored orthorhombic dipyramidal crystals with a dull to earthy luster. It has a Mohs hardness of 5 and a specific gravity of 2.86.