Yellow crystals of the rare vanadium mineral sherwoodite from Polar Mesa, Grand County, Utah, United States of America. Ex.Dr.Hartel collection. — Photo: David Hospital · CC BY-SA 4.0
Sherwoodite
Sherwoodite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ca₄.₅AlV⁴⁺₂V⁵⁺₁₂O₄₀·28H₂O.
It crystallizes in the tetragonal crystal system (space group I4_1/amd).
Key properties: Mohs hardness 2; specific gravity 2.8; Pale blue streak; Vitreous to earthy luster; optically uniaxial.
IMA symbol Swd, grandfathered status — known before the IMA’s founding, named in 1958.
An oxidation product of lower valent vanadium minerals, on fracture surfaces and replacing fossil wood in Colorado Plateau-type U–V deposits; likely widely distributed.
It is found associated with Selenium, metatyuyamunite, melanovanadite (Colorado Plateau, USA); pascoite, pyrite, copper, gypsum, patrónite, melanovanadite (Minasragra, Peru).
The mineral was named to honor Alexander M. Sherwood (1888–?), American analytical chemist, U.S. Geological Survey.