Tetragonal; habit prismatic.
G = 4·4-4·8; H = 41⁄2-5. Brown to black.
Various localities in Scandinavia.
Thorogummite.
UO₃,3ThO₂,3SiO₂,6H₂O? An altered [Mackintoshite] (q.v.)? ThO₂ = 41·4; E₂O₃ = 6·7%.
Usually massive; sometimes in crystals resembling Zircon.
G = 4·43-4·54. H = 4-41⁄2. Dull brown; opaque.
Llano Co., Texas.
Thortveitite.
E₂O₃,2SiO₂, with Fe´´´, Al, Mn´´´ traces; E = chiefly Sc. Yttr = 54·5%.