230 K. JiMBo : 



ordinary vicinal faces on ±R and are conjectured to be due to 

 etching. 



Chalcedony and agate are chiefly found in the provinces 

 Kaga, Etchij, Izumo, &c. Dark-green to green compact quartz 

 is found in the provinces of Izumo, Echigo, &c. All these oc- 

 currences of quartz varieties have been described by Otsuka, 

 Hiki, &c. 



Pseudomorphs of quartz after calcite in co P. oP were found 

 at OsAWA near Nikkö in Shimotsuke Province ; those after sharp- 

 pointed rhombohedra of calcite were found in Ming Province. 

 Top-shaped chalcedonies from the provinces of Uzen, Echigo, &c., 

 seem to be pseudomorphs after broken pieces of some spherical 

 mineral-aggregate with radial-fibrous structure and consist of two 

 flat cones united at bases. They have a diameter of about 1 to 

 1.5 cm. The apex of the cones is provided either with a rounded 

 prominence or a depression. For the pseudomorphs of quartz 

 after barite, see under Barite. 



34. Tridymite. 



In the stone-quarry of Göroyama close by the town of 

 Nagano in Shinano Province and in that of Shimazaki on tlie 

 west of Kumamoto in Higo Province, there exist andésite expo- 

 sures with loose enclosures and seggregations. In these rocks 

 tridymite is abundantly found as irregular scales and tabular 

 crystals. Associated with it are found a few breislakite (?) 

 needles in some of the specimens from these localities. At 

 Göroyama, Yamasaki has observed a very pretty trichroic 

 cordierite crystal of very minute size. Tridymite from Shimazaki 

 is usually more transparent than that from Göroyama, although 

 the characteristic optical anomaly, as well as twinning crystal- 



