Akdalaite

Very rare mineral

5Al₂O₃·H₂OIMA symbolAkdIdentificationColorWhite, pale greenish yellow in thin sectionFractureIrregular/unevenMohs scale hardness7–7.5LusterVitreousStreakWhiteDiaphaneityTranslucentSpecific gravity3.68

Akdalaite (IMA symbol: Akd^[1]) is a very rare mineral found in Kazakhstan and has the formula 5Al₂O₃·H₂O.^[2] It was formerly believed to be 4Al₂O₃·H₂O. It is therefore the same as tohdite an artificially produced phase. Studies on the crystal structure and spectra indicate that this is an aluminium oxide hydroxide.^[3]

References

^ Warr, L.N. (2021). "IMA-CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ A New Occurrence and New Data on Akdalaite, a Retrograde Mineral from UHP Whiteschist, Kokchetav Massif, Northern Kazakhstan, Shyh-Lung Hwang, Pouyan Shen, Hao-Tsu Chu, Tzen-Fu Yui, International Geology Review, 48, 8, 2006, 754-764, doi:10.2747/0020-6814.48.8.754
^ Ab-initio quantum mechanical study of akdalaite (5Al2O3· H2O): structure and vibrational spectrum, Demichelis, R.; Noel, Y.; Zicovich-Wilson, C. M.; Roetti, C.; Valenzano, L.; Dovesi, R., Journal of Physics: Conference Series, Volume 117, Issue 1, pp. 012013 (2008)., doi:10.1088/1742-6596/117/1/012013