Grunerite from Garnet-Ankerite-Siderite Magnetite Assemblage from Huliyar, Tumkur District, Karnataka

Grunerite is a characteristic mineral of metamorphosed iron-rich siliceous sediments. Though it occurs commonly in the oxide, silicate and carbonate facies of banded iron formations, its association with ankerite, garnett siderite and magnetite appears to be somewhat rare. Detailed petrographic, optical ana chemical studies together with X-ray diffraction pattern of the separated amphibole from the ankerite-siderite-garnet assemblage from Huliyar indicate that the amphibole belongs to the grunerite end member [82% Fe₇Si₈O₂₂(OH₂)] of the cummingtonite-grunerite series.