Woodallite
Woodallite is an IMA-recognized mineral species in the halide class, with the chemical formula Mg₆Cr₂(OH)₁₆Cl₂·4H₂O.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Hydrotalcite structural group.
Key properties: Mohs hardness 1.5–2; specific gravity 2.062; Pale pink to white streak; Resinous to waxy luster; optically uniaxial.
IMA symbol Wod, IMA status: approved, named in 2000.
Found in a low-grade, disseminated nickel sulfide deposit in lizardite+brucite-altered dunite formed by hydrothermal alteration of primary magmatic chromite by Cl-rich solutions at temperatures < 320oC.
It is found associated with Chromite, lizardite, brucite, iowaite, pentlandite, magnetite, tochilinite.
The mineral was named to honor Australian geologist Roy Woodall (b. 1930) who was instrumental in the initiation and development of the nickel and alumina industries in Western Australia.