Hewettite Locality: Gold Quarry Mine (Maggie claims), Maggie Creek District, Eureka County , Nevada , USA ( Locality at mindat.org ) Size: 6.1 x 5.9 x 2.7 cm. Hewettite is a rare calcium vanadate hydrate. This fine specimen from the Gold Quarry Mine of Nevada is richly covered with radial, divergent sprays of lustrous, brassy to chocolate-brown hewettite needles. The largest spray is 9 mm across and the blocky, brecciated limestone matrix is nicely accented with drusy, yellow carbonate-fluorapatite. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Hewettite
Hewettite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CaV⁵⁺₆O₁₆·9H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Hewettite structural group.
Key properties: specific gravity 2.51–2.61; Silky to adamantine luster; optically biaxial.
IMA symbol Hew, grandfathered status — known before the IMA’s founding, named in 1914.
Occurs as an alteration product of patronite (Minasragra, Peru); an alteration product of less-oxidized vanadium minerals in Colorado Plateau-type U–V deposits.
It is found associated with Metahewettite, corvusite, montroseite, rauvite, steigerite, fervanite, navajoite, carnotite, tyuyamunite (Colorado Plateau deposits, USA).
The name refers to Donnel Foster Hewett (1881–1971), geologist with the U.S. Geological Survey, who described the mineralogy of Minasragra, Peru.