Abstract
Edingtonite from the bedded manganese ore deposit of the Shiromaru mine, Tokyo, is found as a subordinate constituent of a thin fissure dominantly filled with celsian. It cuts a low grade manganese ore composed of braunite, hematite, cymrite, celsian and albite. The microprobe analysis gave: Si02 35.82, Al2O3 20.26, BaO 30.36, and the calculated H2O 14.35, total 100.79%. The empirical formula is: Ba1.00Al2.OOSi3.00O10•4H2O (basis:O=10 in the anhydrous part). X-ray powder pattern is indexed on an orthorhombic cell with a=9.542, b=9.654, c=6.514 Â. It is the later product than celsian in the fissure, where the aggregate of compositionally varied grains (Cn92Or8 to Cn79Or21) occupies the wall side portions, probably reserving the original texture. The close co-existence of feldspars and zeolites characterized by the same cations such as Na, Ca and K has not been known. But in case of Ba, the co-existence of these two tectosilicates has been hereby confirmed probably as the first example. It is worth alluding to that both of them have the four-membered ring composed of (Si, Al)O4 as the basic units of the tectosilicate frame-work.
