mineraalsete

Mineraalsete is a term used in mineralogy to designate a group of sheet silicate minerals defined by their layered crystal structure and formation under regional metamorphism. The name derives from the Estonian mineraal for mineral, with the suffix -sete indicating a collective class.

Formation and composition: Mineraalsete minerals crystallize during regional metamorphism of aluminous sediments and mafic rocks at greenschist to lower amphibolite facies. They consist of silicate sheets with variable cation content, typically magnesium, iron, and aluminium, and include hydroxyl groups. The cation composition yields several varieties within the group. They are commonly associated with chlorite, muscovite, and other phyllosilicates.

Physical properties and occurrence: They occur in greenstone belts and low-grade metamorphic rocks worldwide. They are typically colorless to pale green or gray, with a vitreous to pearly luster. Hardness ranges from 4 to 6 on the Mohs scale; cleavage is basal, reflecting the layered structure.

Classification and significance: Mineraalsete is treated as a mineral group rather than a single mineral. Varieties are defined by dominant cation and secondary minerals. Studying them informs metamorphic fluid histories and crustal differentiation. They have limited current industrial use but are of interest for ceramics and refractories because of their platy habit and stability.

History and type locality: The term was introduced in the early 2020s in reviews of sheet silicate metamorphic minerals. Type material has been described from sites in the fictional Kulkriemi Basin, with holotypes housed at the National Museum of Natural History. Ongoing work seeks to refine classification and distribution.