White vitreous crystal aggregates of the extremely rare Al mineral akdalaite from the TL (Solnechnoye Mine, Kara-Oba, Karazhal, Ulytau Region, Kazakhstan) and only one of 6 known localities worldwide. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Akdalaite
A very rare hydrated aluminium oxide from Kazakhstan, now considered the natural counterpart of the synthetic phase tohdite.
Intro adapted from Wikipedia (CC BY-SA).
Akdalaite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Al₁₀O₁₄(OH)₂.
It crystallizes in the hexagonal crystal system (space group P6_3mc). It is a member of the Nolanite structural group.
Key properties: Mohs hardness 7–7.5; specific gravity 3.68; Vitreous to porcelaneous luster; optically uniaxial.
IMA symbol Akd, IMA status: approved, named in 1969.
Found in veinlets cutting amesite-fluorite-muscovite rock and fluorite-magnetite-diopside- vesuvianite skarn.
It is found associated with Muscovite, fluorite, amesite, magnetite, diopside, vesuvianite, andradite.
The name refers to the Kazakh name, Akdala, for the vicinity of Kara-Oba, Kazakhstan.