W at anabe— Babingtonite from Japan. 159 



Art. XV. — On the Babingtonite from the Contact Meta- 

 morphic Deposits of the YakuJci Mine, Province Iivaki, 

 Japan; by Manjiro Watanabe. 



Mode of occurrence. 



The Yakuki mine is located near the eastern margin of 

 the Abukuma mountainland, 1 in the Province of Iwaki, in 

 northeastern Japan. It has been worked for chalcopyr- 

 ite in the skarn 2 masses, which were formed in the contact 

 aureole between granodiorite and the Paleozoic clay slate 

 and limestone. The minerals, constituting the ore 

 deposits, are chiefly hedenbergite and garnet with some 

 chalcopyrite. Magnetite and sphalerite are also found 

 in notable amounts in some portions. The babingtonite, 

 to be described, occurs in veins and irregular aggregates, 

 mainly in the hedenbergite masses in the western part of 

 the mine. In some specimens, these masses of babington- 

 ite, cut by garnet, are brecciated into small fragments. 

 Some of these fragments are surrounded by thin layers 

 of babingtonite, on which minute crystals of garnet are 

 planted. Thus, it is clearly seen that these two minerals 

 were repeatedly deposited one after the other. 



These fragments in the brecciated zone are usually 

 cemented by quartz or calcite. In the latter case, the 

 crystals of babingtonite, planted on the fragments, are 

 easily isolated by dissolving the carbonate in acid. 



In other cases, the babingtonite appears in minute vein- 

 lets, which cut the hedenbergite, magnetite and ilvaite. 3 

 Such veinlets often thin out in one direction. The wider 

 portion is filled with garnet, and the narrower portion is 

 made of garnet and babingtonite, the former mineral 

 appearing implanted on the walls. In still narrower 

 parts, babingtonite occurs with quartz, and the veinlet 

 terminates as a pure aggregate of quartz. 



1 B. Koto: The Archean formation of the Abukuma Plateau, Jour. Coll. 

 Sci. Imp. Univ. Tokyo, vol. 5, Pt. 3, 1893. 



2 This term was originally a Scandinavian miner 's word, which means rub- 

 bish. However, it was applied by V. M. Goldschmidt to a certain type of 

 contact metamorphic rock, which consists essentially of coarse-grained aggre- 

 gates of pyroxene and garnet, and is now widely used with this meaning. 



3 This mineral is found in very small amount, and is not accurately deter- 

 mined. It is black in color, and is generally opaque, but transmits light in 

 very thin portions, where the pleochroism is marked. It is easily attacked 

 by hydrochloric acid. It is most probably ilvaite. 



Am. Jour. Sci.— Fifth Series, Vol. IV, No. 20.— August, 1922. 

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