:Locality: Kovdor Phlogopite Mine, Kovdor Massif, Northern Region, Russian Federation Size: 2.3 × 2.1 × 1.5 cm Description: Golyshevite crystals in matrix, some of them showing a pseudohexagonal section, with the typical yellowish-brown zircon-like colour. Under loupe you can observe faces. Golyshevite is an extremelly rare species, with Type Locality in this mine, nowadays closed and restored. — Photo: Joan Rosell , from rosellminerals.com · CC BY-SA 4.0
Golyshevite
A rare carbonate-bearing eudialyte-group mineral with cyclic silicate rings in its structure.
Intro adapted from Wikipedia (CC BY-SA).
Golyshevite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₁₀Ca₉Zr₃Fe₂SiNb(Si₃O₉)₂(Si₉O₂₇)₂(OH)₃(CO₃)·H₂O.
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Eudialyte structural group.
Key properties: Mohs hardness 5.5; specific gravity 2.89; White streak; Vitreous luster; optically uniaxial.
IMA symbol Gsv, IMA status: approved, named in 2004.
Found in a calcium-rich peralkaline pegmatite.
It is found associated with Cancrinite, aegirine-augite, hedenbergite, orthoclase, pectolite, thomsonite-Ca, tacharanite, calcite.
The mineral was named to honor сгуstallographer Vladimir Mikhailovich Golyshev (1943-2000), Mordvinian State University, Saransk, Russia.