Porous masses and crusts of glassy grey mansfieldite from the type locality associated to sky blue unknown crystals. — Photo: David Hospital · CC BY-SA 4.0
Mansfieldite
An aluminium arsenate of the variscite group, named for USGS geologist George Mansfield.
Intro adapted from Wikipedia (CC BY-SA).
Mansfieldite is an IMA-recognized mineral species in the arsenate class, with the chemical formula Al(AsO₄)·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Pbca).
Key properties: Mohs hardness 3.5; specific gravity 3.03; Vitreous luster; optically biaxial.
IMA symbol Mfd, grandfathered status — known before the IMA’s founding, named in 1948.
A hydrothermal product in altered and mineralized andesitic pyroclastic rocks (Hobart Butte, Oregon, USA).
It is found associated with Kaolinite, quartz, scorodite, realgar, stibnite (Hobart Butte, Oregon, USA).
The mineral was named to honor Dr. George Rogers Mansfield (1875–1947), U.S. Geological Survey.