Yellow, acicular aggregates of haynesite on claystone from the type locality, Repete Mine in Utah, USA. (field of view: 2.9 mm) — Photo: BLFrank · CC BY-SA 4.0
Haynesite
Haynesite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (UO₂)₃(Se⁴⁺O₃)₂(OH)₂·5H₂O.
It crystallizes in the orthorhombic crystal system.
Key properties: Mohs hardness 1.5–2; specific gravity 4.1; Vitreous luster; optically biaxial.
IMA symbol Hay, IMA status: approved, named in 1990.
Rare in an oxidized uranium deposit in mudstones and sandstones.
It is found associated with Andersonite, boltwoodite, ferroselite, gypsum, barite, calcite.
The mineral was named to honor Patrick Eugene Haynes (1953-), American geologist, mineral collector and dealer, who found the first specimens.