Olive brown single crystal group of the extremely rare Sn-Nb-Ta mineral foordite in a completely analyzed specimen by SEM/EDS, from Kubitaka, Punia, Maniema, DR Congo. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Foordite
Foordite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Sn²⁺Nb₂O₆.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 6; specific gravity 6.734; Yellowish white streak; Vitreous to adamantine luster; optically biaxial.
IMA symbol Foo, IMA status: approved, named in 1984.
A very rare mineral, in an alluvial pebble originating from a highly differentiated granite pegmatite, formed under reducing conditions deficient in Fe, Mn, Na, Ca, and F (Lutsiro, Rwanda).
It is found associated with Ferrocolumbite, cassiterite, stannoan plumbomicrolite, ixiolite (Lutsiro, Rwanda).
The mineral was named to honor Dr. Eugene Edward Foord (1946–1998), American mineralogist with the U.S. Geological Survey, Denver, Colorado, USA, student of granite pegmatites.