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.

Nenadkevichite
Nenadkevichite with ancylite crystals on the side
General
CategoryCyclosilicate
Formula
(repeating unit)
(Na,Ca)(Nb,Ti)Si2O7·2H2O
Strunz classification9.CE.30a
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPbam
Identification
ColorRose-pink, very light pink, light yellow, brown; dark brown due to inclusions
CleavagePoor/indistinct
FractureIrregular/uneven
TenacityBrittle
Mohs scale hardness5
LusterVitreous, dull
StreakWhite, very light rose-pink
DiaphaneityTransparent, translucent, opaque
Specific gravity2.78 – 2.885 g/cm3

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

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