Nenadkevichite

Nenadkevichite
Nenadkevichite with ancylite crystals on the side
General
Category	Cyclosilicate
Formula (repeating unit)	(Na,Ca)(Nb,Ti)Si2O7·2H2O
Strunz classification	9.CE.30a
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pbam
Identification
Color	Rose-pink, very light pink, light yellow, brown; dark brown due to inclusions
Cleavage	Poor/indistinct
Fracture	Irregular/uneven
Tenacity	Brittle
Mohs scale hardness	5
Luster	Vitreous, dull
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 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