Mansfieldite

Mansfieldite
General
Category	Mineral
Formula (repeating unit)	AlAsO4·2H2O
IMA symbol	Mfd[1]
Strunz classification	08.CD.10
Dana classification	40.04.01.04
Crystal system	Orthorhombic
Crystal class	Orthorhombic-Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pbca
Unit cell	876.8 ų
Identification
Formula mass	201.93 gm
Color	White, light gray
Crystal habit	Spherical, encrustations
Cleavage	Indistinct on {201} and on {001} and {100} in traces
Fracture	Sub-conchoidal
Mohs scale hardness	3.5–4
Luster	Vitreous
Streak	White
Diaphaneity	Transparent, transculent
Specific gravity	3.03
Density	3.03
Optical properties	Biaxial (+)
Refractive index	nα = 1.622 – 1.631 nβ = 1.624 – 1.649 nγ = 1.642 – 1.663
Birefringence	0.020 – 0.032
2V angle	Measured 30°–68°, calculated 38°–82°
Dispersion	None
Common impurities	Cobalt

Mansfieldite is an uncommon mineral that was named after an American geologist, George Rogers Mansfield. It has been considered a valid species since 1948. It is a member of the variscite group. Mansfieldite creates a series with scorodite, and it is the aluminium analogue of said gem. Mansfieldite is colorless in transmitted light.^[2] It is mostly made out of oxygen (47.54%). Other components include arsenic (37.1%), aluminium (13.36%) and hydrogen (2%).^[3] Mansfieldite crystals form due to hydrothermal origin in altered and mineralized andesitic pyroclastic rocks. Due to its size, mansfieldite is hard to see even under a microscope. The pink variation of the mineral is due to cobalt impurities, otherwise it is white to light gray. It can be found in the US, Mexico, France, Algeria, England, Australia, Germany, Algeria and Kazakhstan.^[4]