GEOLOGY AKD MINERAL EESOUECES OF SIKHIM. 63 



The following generalisations arrived at by Mr. 'Mallet with 

 regard to the copper ores of the Darjeeling district generally hold 

 true for Sikhim also : — 



(1) "All the known copper-bearing localities are in the Daling 

 beds. Some are, it is true, situated in the transition rocks between 

 the Dalings and the gneiss, but none in the genuine gneiss itself. 



(2) "The ore in all is copper pyrites, often accompanied by 

 mundic. Sulphate, carbonate, and oxide of copper are frequent as 

 results of alteration of the pyrites, but they occur merely in traces. 



(3) "The ore occurs di.^seminated through the slates and schists 

 themselves, and not in true lodes."* 



Witii regard to the first generalisation, it may be noted that 

 copper ores have been found at several places noted below, in the 

 gneiss itself, though usually within a short distance of its junction 

 with the Dalings. The gneiss ores, however, do not appear to be 

 so rich as those in the Dalings, and have never been worked. With 

 regard to the third generalisation, the ore in one case at least, that 

 of Pachikhani, appears to occur in true lodes. 



Within the Dalings, the richest ores (those of Pachikhani and 

 Rathokhani, for instance) occur amongst greenish, rather soft, slaty 

 shales. The gangue in this case consists of the shale, much hardened 

 by infiltrated quartz, or of quartz alone. 



The method of copper-mining adopted in Sikhim is very similar 

 to that generally pursued in India in most native operations, and has 

 been fully described by Mr. Mallet in his geological account of Dar- 

 jeeling. His description, t with some additions, is, however, repeated 

 here for easy reference. 



The Sikhim mines greatly resemble magnified rabbit-holes: 

 meandering passages are excavated with little or no system beyond 

 following, as far as possible, the direction of the richest lodes ; and 

 although some precaution is taken to support the roof in the more 

 shaky places by timber props, the number of galleries fallen in or 

 abandoned show how inefficiently this is done. The shafts are 

 always driven vertically in from the face of a cliff or declivity, as no 

 attempt at systematic pumping is ever made. Should the shaft become 

 flooded or too damp to permit of the water being kept down by 

 gravitation or simple bailing, it has to be abandoned. Poor shafts 

 are immediately deserted if richer ore is found near, long before the 

 former, under a better system, would be worked out. 



The passages vary according to the height and thickness of the 

 lode, and average about three to four feet in height and width ; but 



• Memoirs, Vol. XI, pt. 1, p. 72. | t Op. cif., p. 69. 



