TIN. 141 



These mines and their associated smelters form the most success- 

 ful mineral enterprise in Yunnan at the present time. 



According to Leclere, the deposits are found at altitudes of 

 2,000 to 2,700 metres above sea-level in the mountains between 

 Meng-tzu, Lin-an Fu and the Red River. The deposits are not 

 entirely alluvial ; they are obviously vein deposits. The cassi- 

 terite is always enclosed in a red clay, sometimes found in fissures 

 of the limestone, at other times in the soil near them. The mineral 

 is derived from the denudation of the upper portions of ancient 

 lodes. As exploitation goes deeper, foreign metals appear and 

 finally predominate, at first as oxides and later as sulphides. The 

 deposits owe their origin to the tourmaline pegmatites which are 

 injected through the lower strata up to the Lower Trias limestones. 

 It is, however, worth noting that even in the upper deposits occur- 

 ring in the midst of porphyries, analysis shows the presence of 

 considerable amounts of tan. 



At the time of Rocher's visit in 1872, silver, copper, zinc and 

 iron were being worked as well as tin, but all the others have long 

 since ceased to be produced, perhaps owing to the increased cost 

 of fuel. 



When Mr. W. F. Collins visited the region about 30,000 men 

 were engaged in the mining, concentration and smelting of the 

 ore; this was all reduced locally, and the metal exported to 

 Hong Kong via Ton-king, and thence, after refining, the greater 

 part passed to Europe. The deposits then worked were all of 

 alluvial origin, and the mines, some 150 in number were scattered 

 over an area about 25 miles long by 20 miles broad. The ore, 

 usually of sand-grain size, was found in highly ferruginous bedded 

 deposits. The underground ores generally contained a little mag- 

 netite and as much as 55 per cent, of hematite together with small 

 percentages of lead. The deeper alluvial deposits were worked 

 from inclined tunnels through the upper layers. Mr. Collins des- 

 cribed the local methods of mining, dressing and concentration in 

 detail. 



Deprat believes it is unlikely that other tinstone deposits will 

 be found in Eastern Yunnan outside the Red River region, as the 

 geological formations are not favourable. I hold similar, views 

 regarding those parts of Western and Central Yunnan that I have 

 traversed. 



