alumiiniksis
Alumiiniksis is a term found in some Estonian-language mineralogy and geology texts used to refer to alumin silicate minerals with the general formula Al2SiO5. The group comprises three well-known polymorphs: andalusite, kyanite, and sillimanite. These minerals form under metamorphic conditions and are valued for their distinctive crystal structures and high thermal stability. The different polymorphs occupy different stability fields: andalusite typically forms at lower temperatures and pressures, sillimanite at higher temperatures, and kyanite under relatively high pressures. The trio reflects how slight changes in pressure and temperature during metamorphism influence mineral structure.
Structure and properties characteristically involve a framework of silicon and aluminum in tetrahedral coordination, with distinct
Occurrence and formation commonly involve regional and contact metamorphism of pelitic and aluminous precursor rocks. They
See also: aluminosilicates, andalusite, kyanite, sillimanite. Note that the term alumiiniksis is not universally standardized in