24 DISTRIBUTION OF MINERAL IN SARAWAK 



ing and accumulation of ore from a kind of top-hole, which is 

 represented by the small vein. 



The veins are natural fissures in the limestone, having" their 

 walls usually clear and well defined, and the adjacent rock is 

 seldom metamoi phosed to any noticeable degree. In the Busan 

 hills the lodes have a general N. W and N. S. and strike and dip at 

 angles varyiug from 20° to 50°, the amount of dip not being a 

 constant in the same lode ; but in the Jambusan valley, about a 

 mile distant, a lode was found striking almost due E. and W. and 

 this was at a considerably lower level than the Busan veins, of 

 which a series of four or perhaps five distinct lodes is to be 

 observed cropping out in one spot, each above the other, with 

 short intervals. The lodes at Bidi are said to dip at a very 

 high inclination, but I have had no opportunity of examining 

 this locality. The working face ranges from six feet to a few 

 inches in depth, and the yield of any single vein is very in- 

 termittent. 



The adventitious minerals, found associated in the vein with the 

 sulphide, are gold and copper in the gangue, and gold, silver, native 

 arsenic and realgar in the ore. The last-mentioned sometimes 

 spots the sulphide of antimony with small pockets of orange-red 

 crystals, and the ore at Bidi is not unfrequently stained red from 

 the same source. The existence of quicksilver also in some form 

 or other is attested by the presence of globules of metallic mer- 

 cury in the flues of the reverberatory furnaces, where it has con- 

 densed after sublimation in the smelting chamber, and has been 

 deposited together with the white oxide of antimony. 



In seeking to decipher the geological sequence of events which 

 resulted in the produce of the system of antimony veins in upper 

 Sarawak, the observer is at once brought face to face with rival 

 theories of the production of mineral veins as a whole. There is 

 no evidence to indicate that the antimony lodes derive their me- 

 tallic contents by any process of segregation from the rock in 

 which they lie, although portion of the gangues may have been 

 locally so derived ; and the true interpretation of the phenomena 

 they present is therefore limited to the inquiry, whether the va- 

 rious minerals were injected in molten state into the including 

 fissures, or were deposited gradually and from solution, by the 

 passage of hot spings through the limestone rock. I do not 

 feel competent to give an opinion on a theoretical matter of this 

 kind, which, to be at all reliable, must be founded on a wide 

 knowledge of strictly chemical geology ; but I may here state 

 that M. Groger, a geologist and mining engineer employed by 



