The crystal structure of vivianite contains Fe2* ions in isolated Fef,* octahedra and in pated fet"* octahedra. Mcissbauer spectral measurements of vivianites mechanically ground in air demonstrate that Fe3*/Fel* increases with rising Fe3* concentration, suggesting that there is a greater probability of oxidizing remaining Fef,* ions than the second Fe2s* ion of an existing n!3*-fe."* pair. A m...

Although a 'chlorite' is usually simple to recognize in thin section because of its characteristic colour, form, and often very low or anomalous interference colours, the identification of the various species is more difficult and requires both chemical and X-ray work for accurate determination. Roy and others have demonstrated that chlorites are polymorphous and occur in two structural groups,...

Abstract. Zinkgruvanite, ideally Ba4Mn42+Fe23+(Si2O7)2(SO4)2O2(OH)2, is a new member of the ericssonite group, found in Ba-rich drill core samples from sphalerite- and galena- diopside-rich metatuffite succession Zinkgruvan mine, Örebro County, Sweden. Zinkgruvanite associated with massive baryte, barytocalcite, diopside minor witherite, cerchiaraite-Al, sulfide minerals. It occurs as subhedral...

The prograde, high pressure, transition from antigorite serpentinite to enstatite-olivine rock occurs along a tectonically undisturbed pro®le at Cerro del Almirez, SE Spain. The reactant assemblage is antigorite + olivine with tremolite rimming precursor diopside. The product assemblage of tremolite + chlorite + enstatite + olivine has a spinifex-like texture with arborescent or radiating olivi...