| Nenadkevichite | |
| Category: | Cyclosilicate |
| Strunz: | 9.CE.30a |
| System: | Orthorhombic |
| Class: | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Symmetry: | Pbam |
| Color: | Rose-pink, very light pink, light yellow, brown; dark brown due to inclusions |
| Cleavage: | Poor/indistinct |
| Fracture: | Irregular/uneven |
| Tenacity: | Brittle |
| Mohs: | 5 |
| Luster: | Vitreous, dull |
| Streak: | White, very light rose-pink |
| Diaphaneity: | Transparent, translucent, opaque |
| Gravity: | 2.78 – 2.885 g/cm3 |
Nenadkevichite is a rare silicate mineral containing niobium with the chemical formula . 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.
It was first reported in 1955 from a nepheline syenite pegmatite in the Kola Peninsula. In addition it has been reported from Mont Saint-Hilaire, Canada; the Ilimaussaq complex, Greenland; Windhoek District, Namibia; and Zheltye Vody, Ukraine. It was named after Konstantin Avtonomovich Nenadkevich (1880–1963), Russian mineralogist and geochemist.