Nenadkevichite: Properties and Occurrences

Nenadkevichite is an orthorhombic hydrated silicate of sodium, calcium, niobium, and titanium, which occurs as pale yellow crystals. It is a rare silicate mineral containing niobium with the formula: (Na, Ca) (Nb, Ti)Si2O7·2H2O. It was named in honor of Konstantin Avtonomovich Nenadkevich who was a Russian mineralogist and geochemist for the A.E. Fersman Mineralogical Museum in Moscow, Russia.

General Information

  • Category: Cyclosilicate
  • Formula: (repeating unit) (Na, Ca) (Nb, Ti)Si2O7·2H2O
  • Crystal system: Orthorhombic
  • Crystal class: Dipyramidal (mmm)
  • Color: Rose-pink, very light pink, light yellow, brown; dark brown due to inclusions.

Properties

Nenadkevichite is a rare silicate mineral containing niobium. 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. The crystal structure, like the other members of the labuntsovite nenadkevichite group, contains columns formed by (Nb, Ti)-octahedra with shared trans-vertices.

  • 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

Occurrences

Nenadkevichite was first reported in 1955 from a nepheline syenite pegmatite in the Kola Peninsula. It is a rare mineral that occurs “between crystals of microcline in a nartolite-albite-rich pegmatite in nepheline syenite in a differentiated alkalic massif” at its Russian locality in the Lovozero massif, and “in pegmatites, cavities in igneous breccias, hornfels, and marble xenoliths in an intrusive alkalic gabbro-syenite complex at the Mont Saint-Hilaire locality in Canada.

In addition it has been reported from Mont Saint-Hilaire, Canada; the Ilimaussaq complex, Greenland; Windhoek District, Namibia; and Zheltye Vody, Ukraine. Other localities include Greenland and newer localities in China, the United States, and Namibia. It was named after Konstantin Avtonomovich Nenadkevich (1880–1963), Russian mineralogist and geochemist.Association: Microcline (Lovozero massif, Russia); microcline, aegirine, catapleiite, ancylite, epididymite, eudialyte, s¶erandite, pectolite, apophyllite, monteregianite, vesuvianite, many other species (Mont Saint-Hilaire, Canada).

Information Source: