Manganese-bearing Silicate Minerals from Metamorphosed Manganese Formations of India. I. Juddite

Supriya Roy
Department of Geological Sciences, Jadavpur University, Calcutta 32, India

Summary: The manganiferous amphibole juddite has been reported by a number of workers from metamorphosed manganese formations of India. The mineral is developed at the contact of pegmatite and gondite, and associated characteristically with blanfordite (manganoan aegirine-augite) and winchite (manganoan richterite-tremolite). The range of the refractive indices of the mineral and the orientation of the optic axial plane normal to (010) suggest the mineral to be of magnesioriebeckite composition. The 100 Mn2+:(Mn2++Mg+Fe2+) and 100 Fe3+:(Fe3++Alvi+Ti) ratios plotted in the glaucophane-magnesioriebeckite diagram show that eight out of nine analyses (eight new) are grouped under magnesioriebeckite composition range. It may thus be concluded that the juddites generally refer to (manganoan) magnesioriebeckite compositions. In some cases, however, the composition of juddite shows considerable departure from ideal magnesioriebeckite composition and the juddite and winchite (manganoan tremolite-richterite) show evidences of compositional transition, indicating partial miscibility. The juddites have been formed by the interaction of pegmatitic fluid on manganese ore, gondite, and other country rocks such as mica schists and diopside-forsterite marble.

Mineralogical Magazine; June 1970 v. 37; no. 290; p. 708-716; DOI: 10.1180/minmag.1970.037.290.09
© 1970, The Mineralogical Society
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