Akdalaite is a very rare mineral found in Kazakhstan and has the formula 5Al2O3·H2O. It was formerly believed to be 5Al2O3·H2O It is, therefore, the same as tohdite an artificially produced phase. Studies on the crystal structure and spectra indicate that this is an aluminum oxide hydroxide.
Akdalaite as well as hogbomite, kyanite, Zn-bearing staurolite, Mg-chlorite, gahnite, hercynite, quartz, apatite, and zircon, are present as submicrometer-size minerals associated with rutile aggregates occurring as inclusions in garnet porphyroblasts of whiteschist from the Kulet Kol region, Kokchetav Massif, northern Kazakhstan.
Physical Properties
- Cleavage: None
- Color:
- Density: 3.68
- Diaphaneity: Translucent
- Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
- Habit: Tabular – Form dimensions are thin in one direction.
- Hardness: 7 – Quartz
- Luster: Vitreous (Glassy)
- Streak: white.
Chemical Properties
- Formula: 5Al2O3H2O
- IMA Formula: (Al2O3)5H2O
- Elements listed: Al, H, O – search for minerals with similar chemistry.
The akdalaite type specimen, stored in the museum of the All-Russian Institute of Mineral Resources (VIMS) in Moscow, had also been re-examined; it has crystallographic parameters similar to tohdite. It is therefore concluded that crystallographic data of the akdalaite type specimen derived from powder X-ray experiments are in error and that akdalaite is the natural counterpart of tohdite.
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