pluginite

Pluginite is a rare silicate mineral described from Plugin Ridge, Nevada. The name derives from the locality and suggests its characteristic layered habit. The composition is variable within an iron-magnesium-aluminum silicate system, with iron, magnesium, silicon and aluminum as major constituents.

Pluginite crystallizes in the tetragonal system and forms prismatic to tabular crystals. It typically presents a vitreous luster and a color range from olive green to brown. The hardness is about 5.5 to 6 on the Mohs scale; it has a pale gray streak and an uneven fracture. Cleavage is imperfect in two directions.

Geologic occurrence: Pluginite occurs in late-stage pegmatites and hydrothermal veins within metamorphic and igneous terranes. It is commonly associated with quartz, feldspar, biotite, and other iron-magnesium silicates. Formation is linked to high-temperature, low-to-medium pressure conditions during accessory mineral crystallization.

Taxonomy and research: It is considered a layered silicate mineral related to sheet silicates by its sheet-like arrangement of octahedral and tetrahedral sheets. Due to rarity, it has little commercial use; specimens are sought by collectors and are primarily of interest for crystallography and to understanding silicate layering in magmatic systems.