Greenish crystal aggregates of the very rare vanadium mineral hendersonite from one of the cotype localities: Mineral Joe #1 Mine, Paradox Valley, Uravan, Montrose County, Colorado, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Hendersonite
Hendersonite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ca₁.₃(V⁵⁺,V⁴⁺)₆O₁₆·6H₂O.
It is a member of the Hewettite structural group.
Key properties: Mohs hardness 2.5; specific gravity 2.77–2.79; Dark brownish green streak; Vitreous, pearly to subadamantine luster; optically biaxial.
IMA symbol Hdr, IMA status: approved, named in 1962.
Found in thin seams and veinlets through sandstone at the interface between partially oxidized and unoxidized ore in Colorado Plateau-type U–V deposits.
It is found associated with Paramontroseite, simplotite, melanovanadite, sherwoodite, corvusite, pyrite, marcasite (J.J. mine, Colorado, USA).
The mineral was named to honor Dr. Edward Porter Henderson (1898–1992), formerly Curator of Meteorites at the Smithsonian Institution, Washington, D.C., USA.