Vlasovite

Class: Silicates

A late phase in nepheline syenites, syenitic pegmatites, and along the contact zone of a differentiated alkalic massif (Lovozero Massif, Russia) (Anthony et al., 2001—2005). Faceted specimens are extremely rare.

Vlasovite — specimen 0006, photo © NMNHS

Original description: Тихоненкова, Р. П. Казакова, М. Е. [Tikhonenkova, R. P., Kazakova, M. E.], 1961. Власовит — новый силикат циркония из Ловозерского массива [Vlasovite — a new zirconium silicate from the Lovozero Massif] — Доклады Академии наук СССР [Doklady Akademii Nauk SSSR] 137 (4): 944—946 [view in ‘Library’].

Type locality: Vavnbed Mt, Lovozero Massif, Kola Peninsula, Murmansk Oblast, Northwestern Federal District, Russia.

Type material: Mining Institute, Saint Petersburg, Russia, 1037/1; Fersman Mineralogical Museum, Moscow, Russia, 83207, vis5052; École Nationale Supérieure des Mines de Paris, Paris, France (Anthony et al., 2001—2005).

Etymology: named after Kuzma Alekseevich Vlasov, Russian mineralogist and geochemist.

Distribution: Ascension Island; Canada: Sheffield Lake complex, Kipawa River, Quebec; Russia: Kola Peninsula; north of Lake Baikal, Siberia (Anthony et al., 2001—2005).

Chemistry

Na2ZrSi4O11

Essential elements: oxygen (O), sodium (Na), silicon (Si), zirconium (Zr).

Crystal data

Crystallography: monoclinic — prismatic. Crystal habit: in crystals, to 15 cm; more commonly as subrounded to irregularly shaped grains and aggregates of such grains. Twinning: twin plane {010}, uncommon (Anthony et al., 2001—2005).

Physical properties

Cleavage: on {010}, good; on {h0l}, poor (Anthony et al., 2001—2005). Fracture: uneven to conchoidal (Anthony et al., 2001—2005). Tenacity: brittle. Hardness: 6 (Anthony et al., 2001—2005). Density: 2.92—2.97 g/cm3 (Anthony et al., 2001—2005). Luminescence: altered portions fluoresce brownish yellow under SW UV (Anthony et al., 2001—2005).

Optical properties

Colour: colourless, pink, pale brown, silvery; in transmitted light, colourless (Anthony et al., 2001—2005). Diaphaneity: transparent (Anthony et al., 2001—2005). Lustre: vitreous. Refractive index: 1.605—1.625 — anisotropic [biaxial (-)] (Anthony et al., 2001—2005). Birefringence: 0.02. Dispersion: distinct (Anthony et al., 2001—2005). Pleochroism: none.

Material from ‘Repository’

1 specimen: 0006 — 0.22 ct, Canada, Quebec, Sheffield Lake.

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