Nenadkevichite

(Na,Ca)(Nb,Ti)Si₂O₇·2H₂OStrunz classification9.CE.30aCrystal systemOrthorhombicCrystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)Space groupPbamIdentificationColorRose-pink, very light pink, light yellow, brown; dark brown due to inclusionsCleavagePoor/indistinctFractureIrregular/unevenTenacityBrittleMohs scale hardness5LusterVitreous, dullStreakWhite, very light rose-pinkDiaphaneityTransparent, translucent, opaqueSpecific gravity2.78 – 2.885 g/cm³

Nenadkevichite is a rare silicate mineral containing niobium with the chemical 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.

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.

References

• Webmineral data
• Mindat with location data