Dark grey metallic crystals of the extremely rare Nb mineral edgarite (FeNb2S6) from the type and only known locality worldwide in Russia: Kaskasnyunchorr Mountain, Khibiny Massif, Murmansk Oblast, Russian Federation. Niobium is a very rare chemical element in sulphides ! In fact it is the only single sulphide with Nb! Ex Vandenbroucke Museum collection specimen, from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Edgarite
Edgarite is an IMA-recognized mineral species in the sulfide class, with the chemical formula FeNb₃S₆.
It crystallizes in the hexagonal crystal system (space group P6_322).
Key properties: specific gravity 4.98.
IMA symbol Edg, IMA status: approved, named in 1995.
Found in a feldspar-rich fenitized xenolith in a differentiated alkalic massif.
It is found associated with Ti-V-rich pyrrhotite, Ti-V-rich marcasite, alabandite, monazite-(Ce), phlogopite.
In honor of Dr. Alan D. Edgar (1935–1998), Professor of Petrology, University of Western Ontario, London, Canada, for his work on alkaline rocks.