Ferrotschermakite

Ferrotschermakite is the iron-rich endmember or variety of tschermakite, a mineral in the scapolite group of tectosilicates. It represents a ferric/ferrous substitution series in which iron substitutes for aluminum and sodium within the scapolite framework, giving a composition richer in iron than other tschermakita endmembers.

The mineral forms through high-temperature metamorphic or hydrothermal processes in calc-silicate rock environments, and it commonly occurs with other scapolite minerals such as marialite and meionite, as well as calcite, dolomite, quartz, and accessory minerals like diopside or titanite. Ferrotschermakite can appear as prismatic to tabular crystals and is typically observed in medium to coarse-grained rocks.

Physical properties of ferrotschermakite include a pale to brownish color, with a vitreous to resinous luster. It has a Mohs hardness around 5.5 to 6 and a specific gravity in the general scapolite range (approximately 2.6 to 2.8). The mineral crystallizes in a tetragonal system, with optical properties that reflect its anisotropic nature, though detailed optical data are often reported in specialized mineral references.

Name and etymology trace to the mineralogist Tschermak, with the prefix ferro indicating iron enrichment relative to the iron-poor tschermakite varieties. Ferrotschermakite is studied within the broader context of scapolite-group minerals and their solid-solution relationships, helping to illuminate mineral stability and compositional variations in metamorphic and hydrothermal settings.