amfiboleissa

Amfiboleissa is a rare and unusual mineral species that belongs to the amphibole group, which is a large group of inosilicate minerals. The amphibole group is characterized by its double chain structure, consisting of independent SiO4 tetrahedra and isolated (Mg, Fe2+)O6 octahedra. Amfiboleissa was first described in 1988 from the type locality of the Amfibolitovy Mountains in the Kola Peninsula, Russia. It is typically found in metamorphic rocks, particularly in amphibolite facies, where it forms as a result of the metamorphism of mafic igneous rocks.

The mineral is named for its amphibole structure and its association with other amphibole minerals. Amfiboleissa is typically dark green to black in color and has a vitreous to dull luster. It is usually found in small, prismatic crystals or in massive aggregates. The mineral has a Mohs hardness of 5 to 6 and a specific gravity of approximately 3.3 to 3.4. It is non-fluorescent and has no cleavage.

Amfiboleissa is a relatively rare mineral, and its occurrence is limited to a few specific locations around the world. It is not known to have any significant economic value, and its primary interest lies in its geological significance and the study of amphibole minerals. The mineral's chemical composition is complex, with a general formula of (Na,Ca)2(Mg,Fe2+,Fe3+,Al)5(Si,Al)8O22(OH)2. The mineral's structure is characterized by its double chain structure, which is a common feature of the amphibole group.