Akdalaite

In the structure there are oxygen planes with ABACA sequence (Yamaguchi et al., 1964). In the ab initio model proposed by Demichelis et al. (2008) there are 8 Al atoms located in the octahedral cavities and 2 Al atoms in the tetrahedral ones; two types of irregular AlO6 edge-sharing octahedra; AlO4 vertices-sharing tetrahedra. There are 2 sheets of first-type (a) octahedra, and two sheets with second-type (b) octahedra and tetrahedra (c). Recently (2019) proved to be the Al analogue of ferrihydrite.

History

Activities related to discovery and approval of the group members

Structural context

Akdalaite
Crystal System hexagonalCrystal Class dihexagonal pyramidalSpace Group P63mc
a5.575—12.87 (7.0582)
b5.575—12.87 (7.8804)
c8.761—14.97 (10.0409)
alpha90
beta90
gamma90—120 (114)
volume235.816—2147.319 (669.406)

Based on 5 measurements

Chemical context

Stoichiometric formulas

Akdalaite
mindat.org
  • March 13, 2023Al10O14(OH)2Formerly given as 5Al2O3.H2O.
IMA
  • March 13, 2023Al10O14(OH)2
mineralogy.rocks
  • Aug. 30, 2022(Al2O3)5·H2O

Elements recorded on EPMA

5
Al
5
H
5
O
1
Be
1
F
1
Fe
1
Mg
1
Zn

Physical properties

ColorColor entities, recognized using a custom trained NER model
    • pale greenish yellow
    Color noteOriginal color note from the source
    White, pale greenish yellow in thin section
    StreakStreak entities, recognized using a custom trained NER model
      Streak noteOriginal streak note from the source
      White
      Lustre
      Vitreous
      Fracture
      Irregular/Uneven
      Transparency
      Translucent
      Tenacity
      brittle
      Hardness
      7—7.5
      Calculated density
      3.673