Purple crystal aggregates of the rare mineral mountkeithite from the TL in Mount Keith (Mount Keith, Wiluna Shire, Western Australia, Australia). Only few localities known worldwide. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Mountkeithite
Mountkeithite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (Mg₁₋ₓFe³⁺ₓ)(SO₄)ₓ/₂(OH)₂·nH₂O (x 3x/2).
It crystallizes in the hexagonal crystal system. It is a member of the Woodwardite, Hydrotalcite structural group.
Key properties: specific gravity 2.12; Pearly luster; optically uniaxial.
IMA symbol Mke, IMA status: approved, named in 1980.
Rare in a vein in serpentinite in a disseminated nickel sulfide deposit, formed by low-temperature alteration of stichtite by sulfate-rich solutions.
It is found associated with Stichtite, morenosite, hexahydrite, pyroaurite, pyrite, magnetite, magnesite.
The name refers to the Mount Keith deposit, Australia, in which it occurs.