Arakiite
A rare zinc-manganese mineral that is simultaneously an arsenate and an arsenite — an unusual pairing in mineralogy.
Intro adapted from Wikipedia (CC BY-SA).
Arakiite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula ZnMn²⁺₁₂Fe³⁺₂(As³⁺O₃)(As⁵⁺O₄)₂(OH)₂₃.
It crystallizes in the monoclinic crystal system (space group Cc). It is a member of the Hematolite structural group.
Key properties: Mohs hardness 3–4; specific gravity 3.41; Pale brown streak; Resinous to submetallic luster; optically biaxial.
IMA symbol Ark, IMA status: approved, named in 1998.
From a museum specimen described as representing “ore-bearing matrix”.
It is found associated with Calcite, magnussonite, specular hematite.
The mineral was named to honor Dr. Takaharu Araki (1929-2004), Department of Geophysical Sciences, University of Chicago, Illinois, USA, for his numerous crystal-structure determinations.