White rooseveltite associated to bismoclite and to yellow microcrystals of the very rare mineral zaïrite, from one of the very few known localities worldwide (Tazna, Cerro Tazna, Atocha-Quechisla, Nor Chichas Province, Potosi Department, Bolivia). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Rooseveltite
Rooseveltite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Bi(AsO₄).
It crystallizes in the monoclinic crystal system (space group P2_1/n). It is a member of the Monazite structural group.
Key properties: Mohs hardness 4–4.5; specific gravity 6.86–7.01; Adamantine luster; optically biaxial.
IMA symbol Roo, grandfathered status — known before the IMA’s founding, named in 1946.
Vey rare in cassiterite veinlets in rhyolite-dacite lava flows (Santiaguillo, Bolivia); in the oxidized zone of a breccia pipe (San Francisco de los Andes, Argentina).
It is found associated with Cassiterite (Santiaguillo, Bolivia); preisingerite, bismutite, mixite, zavaritskite, wulfenite (Moldava, Czech Republic); conichalcite, mixite (Uzbekistan).
The mineral was named to honor Franklin Delano Roosevelt (1882-1945), 32nd President of the USA.