Formula: BaMg3(Si2Al2O10)(OH)2
Phyllosilicate (sheet silicate), brittle mica group, barium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.30 measured, 3.33 calculated
Hardness: 2½ to 3
Streak: Yellow-white
Colour: Yellow-brown to colourless
Common impurities: Ti,Fe,Ca,Na,F,H2O

Metamorphic environments


At the Netra manganese project, Balaghat District, Jabalpur Division, Madhya Pradesh, India, barium-bearing micas occur in pockets in manganese oxide-rich rocks enclosed in metapelites. Indications are that metamorphism occurred at about 650oC temperature and 6 kbar pressure.
Micas have developed in manganese oxide-rich rocks where the latter have been invaded by late silicic pegmatite and carbonate veins. In these pockets, the manganese oxide-rich rocks contain braunite, hausmannite, bixbyite-(Mn), barium-bearing mica, K-feldspar, hematite, calcite, dolomite and quartz. Braunite is the most abundant phase, and bixbyite-(Mn) is enclosed in braunite. The micas are secondary in nature and are pseudomorphs after carbonates and K-feldspars. One of the micas approaches closely synthetic end-member kinoshitalite, and there is a complete solid solution between the phlogopite and kinoshitalite end-members (AM 74.200-202).

At the type locality, the Noda-Tamagawa mine, Noda, Kunohe-gun, Iwate Prefecture, Japan, kinoshitalite is found as small scales less than 1 mm across in hausmannite-tephroite ore from the 12th level; it is also found at the 6th level in association with celsian, quartz, spessartine, rhodonite, chalcopyrite and pyrrhotite (AM 60.486-487).

At the Semail Ophiolite, Oman, kinoshitalite was studied in a granulite facies manganese ore associated with calcium- and magnesium- bearing tephroite, hausmannite, calcite and manganese-bearing clinochlore, and in a second assemblage together with hausmannite, altered tephroite, manganese-bearing diopside and calcite. The metamorphic rocks occur enclosed in peridotites and were metamorphosed during ophiolite obduction (The overthrusting of oceanic crust onto the leading edges of continental plates) (AM 85.242-250).

At the Hutter Mine, James River-Roanoke River Mn-Fe-Ba Mining District, Pittsylvania county, Virginia, USA, kinoshitalite has been found in a metamorphosed manganese-bearing marble. The metamorphic grade is middle amphibolite facies, pressure 400 MPa and temperature 575oC. The kinoshitalite occurs in a single layered hand sample containing both skarn and marble layers. Kinoshitalite is scarce and fine-grained in manganese-bearing marble and coexists with kutnohorite, manganese-bearing calcite, fluorine-bearing alleghanyite, fluorine-bearing sonolite, aluminium-bearinng jacobsite and alabandite. Kinoshitalite is both more abundant and coarser-grained in skarn, where it coexists with kutnohorite, tephroite, fluorine-bearing manganhumite, spessartine, jacobsite and manganese-bearing magnetite.
The two likeliest source minerals for the barium in kinoshitalite found here are baryte and barytocalcite (AM 88.40-747).

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