Explanation of Plate VI. (Photomicrographs) 



Fi"-. 1. Chalcedony cnist of the ring-ore from the Daisen vein. Ordinary 

 h"'ht. Magnified 70 diameters. Note the radial and fil)rons structm-e of 

 chalcedony. 



Fig. 2. Ditto between crossed niçois, showing more clearly that chalcedony 

 consists of radiating fihers. C, chalcedony; Q, cinartz gi-ains of later 

 deposition. 



Fig. 3. Thinner crust of chalcedony in another specimen of ring-ore. 8, 

 sulphides, chiefly bornite in association with minute crystals of cassiterite 

 in the earhest crust of quartz ; C, chalcedony crust consisting of globular 

 chalcedony; Q, later crust of quartz. Ordinary light Magnified 50 

 diameters. 



