PIEDMONTITE-SCHIST IN JAPAN. 



The extinction-direction is, of course, parallel and at right angles 

 to the longer sides of sections in the zone of M and T, and the in- 

 tensity of the colours also depends upon the section in this zone. 

 The polarization-colours are magnificent, ranging from an intense 

 violet to an indigo-blue tinge, and this becomes more pronounced 

 if we insert a quartz-plate in the tube of the microscope. 



The piedmontite is generally pure : neither liquid-enclosures, 

 gas-enclosures, nor microlithic interpositions being found in large 

 quantities. Minute crystals represent the ideal purity of the 

 mineral. 



This mineral has been isolated from other constituents of the 

 schist from Otakisan, Awa province, by means of Thoulet's solution. 

 The result of the chemical analysis, kindly undertaken by Mr. J. 

 Takayama, of the Geological Survey of Japan, is as follows : — 



Si0 2 36-16 



A1 2 0 3 22-52 



Fe o 0 3 9-33 



Mn 2 0 3 6-43 



CaO 22-05 



MgO 0-40 



K 2 0 trace 



Na 2 0 0-44 



H 2 0 3-20 



100-53 



H : Ca : : 1 : 2-2 Ca : £ : Si : : 1-25 : 1 : 1-92 



(b) Comparison with other Occurrences. — On comparing the result 

 stated above with analyses of Swedish and Alpine epidotes * our 

 mineral shows in some particulars a marked difference in the per- 

 centage-composition from both of them ; there is nevertheless a 

 general resemblance in all, and the Japanese epidote supplies a 

 hitherto missing link between that of Jacobsberg, in Sweden, and 

 that of St. Marcel, in Piedmont. Mr. Takayama states that he is 

 as yet unable to decide whether the manganese in the Japanese 

 epidote exists as sesquioxide or as monoxide, or as both. Igelstrom 

 suggests that the Swedish mineral contains manganese as the 

 monoxide, while others are of opinion that in the Alpine epidote 

 the manganese exists only in the condition of sesquioxide, Some 

 mineralogists therefore hesitate whether they should be regarded as 

 the same mineral variety f. The writer before expressing himself 

 decisively on this point awaits the results of a more complete 

 examination. 



Being of a very beautiful rose-red colour, highly pleochroic and 

 acicular in habit, piedmontite is frequently confounded with tour- 

 maline, and as such it was at first regarded by us. Dr. E. JSTaumannJ 



* Hauimelsberg, 1 Mineralckemie,' 2te Auflage, p. 595. 

 t Naumann ; Zirkel, ' Elemente der Mineralogie,' 12te Auflage, p. 577. 

 \ 'Ueber den Bau und die Entstehung der japanisehen Inseln,' Berlin 

 1885, p. 10. 



Q.J.G.S. No. 171. 2 k 



