Sample of the mineral Thoreaulite, held in the Harvard Museum of Natural History — Photo: Phoebe · CC BY-SA 4.0
Thoreaulite
Thoreaulite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Sn²⁺Ta₂O₆.
It crystallizes in the monoclinic crystal system (space group Cc).
Key properties: Mohs hardness 6; specific gravity 7.6–7.9; Brown to yellow, slightly greenish streak; Resinous to adamantine on the cleavage luster; optically biaxial.
IMA symbol Tre, grandfathered status — known before the IMA’s founding, named in 1933.
A very rare mineral formed in differentiated granite pegmatites deficient in O, Fe, Mn, Na, Ca, and F.
It is found associated with Cassiterite, lithiotantite, microlite, calciotantite, cesplumtantite (Manono pegmatite, Congo).
The mineral was named to honor Professor Jacques Thoreau (1886–1973), University of Liège, Liège, Belgium, authority on Congolese (Zairian) mineral occurrences.