186 



B. KOTO 



Appendix. 



Notß 1. — The normal sericite-schist, accompanying the pied- 

 montite-beai'ing rock, acquires now and then a coarse-lamellar 

 structure ; and in some case as that of Yanase near Yorii, a 

 cleaved surface of such a rock shows numerous green patches of a 

 fuchsite-]\ke appearance. These patches, after being taken off with 

 a knife-edge and mounted on the object-glass, seem, under the 

 microscope, to consist of sericite-lamella?, together with a large 



numl)er of bundles of 

 smaragd-green needles 

 (0.5 mm. in length), 

 ])eautifn]lv arranged in 

 a radial manner (see the 

 annexed figure). Studied more in detail, each needle is found to be 

 provided with a median ridge, and extinction of light takes place 

 parallel to, and at right angles with, that ridge. The pleochroism is 

 distinct, and the deepest shade of colour is observed, when the longest 

 extension of the needles is at right angles with the shorter diagonal 

 of the lower nicol. Crystal-individuals are usually broken at a regular 

 distance, and the traces of the planes of fracture meet with each other 

 at the median ridge, making an angle of about 90°; this is probably 

 due to the existence of a plane of cleavage or gliding upon one of 

 the brachydomes. By the addition of a few drops of hydrochloric 

 aoid, the green crystals are seen to dissolve readily with vivid effer- 

 vescence, and from this fict as well as from its form and optical 

 properties, the mineral may be said with certainty to belong to 

 nragoniU (Eisenblilthe). Cf. foot-note, page 93. 



