Phlogopite
Image: Didier Descouens (CC BY-SA 3.0)
Mineral NamePhlogopite
Chemical FormulaKMg₃(AlSi₃O₁₀)(F,OH)₂
Mohs Hardness2.5
Crystal Systemmonoclinic
Streak Colorwhite
Cleavageperfect basal on {001}
Fractureuneven to micaceous
Specific Gravity2.83
Colorsyellowish-brown, reddish-brown, golden-brown, green, white
Transparencytransparent to translucent
Type LocalitySan Vito quarry, San Vito, Ercolano, Monte Somma, Somma-Vesuvius Complex, Naples Province, Campania, Italy
Mineral GroupSilicates (Phyllosilicates, Mica Group)
Useselectrical insulation, filler in plastics and paints, collector's specimens
Associated Mineralscalcite, diopside, forsterite, spinel, apatite, magnetite
Raritycommon
Description
The image displays a dense aggregate of small, flaky phlogopite crystals, predominantly in shades of golden-brown to yellowish-brown. Many individual flakes exhibit a translucent quality and a distinct pearly luster, reflecting light with iridescent flashes.
Geological Context
Phlogopite is a common mica mineral found in magnesium-rich igneous rocks, such as kimberlites and lamprophyres, and in contact or regional metamorphic rocks, particularly those derived from dolomitic limestones or ultramafic rocks. Its presence in the Somma-Vesuvius Complex indicates formation in a volcanic or volcanically-influenced metamorphic environment.
