Nenadkevichite with ancylite crystals on the side
|Color||Rose-pink, very light pink, light yellow, brown; dark brown due to inclusions|
|Mohs scale hardness||5|
|Streak||White, very light rose-pink|
|Diaphaneity||Transparent, translucent, opaque|
|Specific gravity||2.78 - 2.885 g/cm3|
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.
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.
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