DISTRIBUTION OF MINERALS IN SARAWAK. 15 



intrusive rocks of igneous origin, so abundant in the district. 

 Associated with this clay, and mostly of more recent date are 

 superficial deposits of puddingstone, river-gravels, &c. 



The intrusive igneous rocks appear indiscriminately all over 

 Upper Sarawak as mountains and hills, and very commonly 

 in the form of dykes, which, with some few reefs of siliceous 

 veinstone, seam the country in great numbers between the more 

 elevated masses. They consist for the most part of varieties of 

 porphyrite, very decomposable, and more seldom of basalt. The 

 volcanic action which caused their eruption would seem to have 

 been in operation at a period subsequent to the formation of all 

 the stratified sedimentary rocks of the district, and antecedent 

 to only the most recent of superficial deposits. It is in im- 

 mediate connection with these rocks that we find the deposits 

 of antimony, arsenic, and cinnabar ; and as there is reason to 

 believe that they occupy fissures caused by the eruption of the 

 volcanic rocks, and that their deposition took place after the 

 cessation of volcanic action, we arrive at a remarkably recent 

 date for the formation of the mineral lodes at Upper Sarawak. 



Such in outline are the geological features of Upper Sarawak. 

 Other formations and many other varieties of rocks, are to be 

 met with in the Territory, but it is not necessary to particularise 

 these, as they are not connected with the mineral deposits of 

 the country, so far as we know, and are therefore foreign to the 

 subject of these notes. 



The minerals and mineral ores of Sarawak, in relation to their 

 local distribution, may be summarized as follows, the names of 

 those which have only been observed in traces being italicized. 



District of Sarawak Proper (including Lundu and Samara- 

 han), — Gold, Antinony, Arsenic, Argentiferous- Arsenic, Cinna- 

 bar, Cobalt, Nickel, Manganese, Copper, Iron Diamond, Aqua- 

 marine,, Coal. 



District of Sadong. — Gold, Coal, Diamond, Iron, Cinnabar. 

 District of Batang Lupar. — Gold, Coal, Iron, Antimony. 

 District of Rejang. — Coal, Iron, Arsenic, Antimony, Nickel, Gold. 

 District of Mukah and Bintulu. — -Coal, Antimony. 



In the districts of Saribas, Kalakah and Oyah, I have no re- 

 liable information of the occurrence of useful minerals. A num- 

 ber of the above mentioned species are known to have bee a 

 detected in other parts of N. W. and W. Borneo beyond the 

 limits of the Sarawak territory, viz., Gold, Antimony, Arsenic, 

 Copper, Cinnabar, Iron, Diamond, and Coal, some in work- 



