550 J. G. H. GODFREY ON THE GEOLOGY OP JAPAN. 



as variegated and grey copper-ore, black oxide of copper, and native 

 copper, are only seldom met with*. A great number of mines are 

 worked for copper, and amongst these the most important are situ- 

 ated in the northern part of Nippon (prov. Eikuehu) and in the 

 island of Shikoku (prov. Iyo and Tosa). At the first locality the 

 lodes usually bear from E. or N.E. to W. or 8.W. Their dip is 

 mostly vertical, and their width varies from a few inches to about 

 3 feet, and may be considered 1 foot on the average ; copper- 

 and iron-pyrites, galena, blende, quartz, clay, and fragments of the 

 containing rock make up the veinstuff. At the Osarizawa mine the 

 containing rock is usually a fine-grained rhyolite, sometimes, also, 

 a metamorphosed clay-slate, and the lodes have a tendency to thin 

 out in the latter. In the Ani district the copper-pyrites is often 

 associated with considerable quantities of galena, and chiefly so in 

 lodes approaching in their bearing to the meridian. The lodes pass 

 here undisturbed through a decomposed rhyolite into the adjoining 

 clay-slate. 



In the neighbourhood of the Besshi mine (prov. Iyo), clay- 

 slate, mica-schist, gneiss, serpentine, and occasionally quartzite 

 are found interbedded, and have a bearing of N.W. to S.E. with a 

 dip of about 50° to the W.E. The lode consisting almost entirely 

 of a mixture of massive iron- and copper-pyrites, and quartz in small 

 quantities, occurs interstratified with the country rock. This lode, 

 varying in thickness from 1 to 10 feet (averaging about 5 feet), 

 has been proved to extend for a length of about 2400 feet and to a 

 depth of about 1400 feet below the outcrop. 



A similarly composed copper-lode occurs at the Tanokuchi mine 

 in the province of Tosa, at the junction of clay-slate and diorite. 

 The lode is from 2 to 3 feet wide, bears E. to W., and dips to the 

 "N. at an angle varying from 40° to 70°. 



Besides the above-mentioned localities, copper-ores are found also 

 in the provinces of Uzen, Hida, Echigo, Echizen, Nagato, andXaga, 

 but the lodes are there much less productive. Out of a total esti- 

 mated production of 3000 tons of copper per annum in Japan, the 

 four first-mentioned mines produce about one half, and the second 

 half is made up by nearly 200 mines distributed over the last-men- 

 tioned provinces. 



(c) Silver. — The silver-ores most frequently found in Japan are 

 silver-glance and antimonial silver (proustite) ; ruby silver (pyrargy- 

 rite), metallic silver, and an alloy of silver and gold (in about equal 

 parts of each) are of rarer occurrence. Usually these ores are associated 

 with other sulphuretted ores, such as copper- and iron-pyrites, galena, 

 and blende. The most common gangue is quartz. Nearly all the 

 silver-lodes have rhyolite as the containing rock ; in exceptional 

 cases only they are found in the older metamorphic group of rocks. 

 The most important silver-mines are situated in the provinces of 

 Sado, Ugo, Eikuehu, Harima, and Hida. 



On the western side of the island of Sado occur three well-defined 

 quartz-lodes, which have been mined during several centuries up to 

 * Eed oxide of copper has not yet been found in Japan. 



