14 DISTRIBUTION OF MINERALS IN SARAWAK 



Briefly described then, this district consists of an ancient 

 compact blue Limestone (Paleozoic ?) on which is superimposed 

 unconformably a thick series of sandstones, conglomerates, and 

 clay-shales, constituting the most extensive series of beds in 

 this part of Borneo ; and on these last lie strata of clay-shales, 

 alluvial clay, river gravels, &c, of very recent origin. Piercing 

 the limestone and sandstone, we find granite and a variety of 

 igneous and trappean rocks — basalt, porphyrite, greenstones, 

 &c, these latter being developed in great abundance in the 

 Antimony districts, where they are in immediate contact with 

 the limestone. The latter formation, in which the lodes of 

 Antimony are seen in sititj is locally rich in fossil organic re- 

 mains, but I am unable to say whether they have been examined 

 by a competent paleontologist with a view to approximate the 

 age of the rock • the planes of stratification can seldom be made 

 out with any approach to certainty, but where they are evident 

 they show that the originally horizontal beds have been up-tilted 

 almost on end and much denuded ; and there is abundant proof 

 that a very considerable interval in time elapsed between the 

 close of the limestone formation, and the commencement of the 

 succeeding sandstone series. 



The sandstone shales have also undergone much disturbance 

 all over this portion of Borneo, although, like the limestone, 

 sometimes retaining their horizontality. They are generally 

 impregnated with per-oxide of iron, and as is so often the case 

 with such rocks, seem quite barren of fossils, except in the 

 coal-measures. It is in this formation that the cinnabar de- 

 posits of the country occur. 



Both limestone and sandstone have been enormously denuded, 

 the latter rising in isolated tabular mountains, or short peaky 

 trends, with an altitude above the sea varying from 1,500 feet 

 and separated by undulating valleys, in which the limestone 

 appears, sometimes in low hilly traets varying from 200 to 1,200 

 feet in elevation, sometimes in solitary crags, but invariably 

 with long lines of old sea-cliffs and bald scarps. When accident 

 removes the veil of dark green jungle from their faces, they 

 present to view surfaces fretted by a thousand deep rifts, and 

 fissured and jointed in every imaginable direction. 



In the intervening lowlands we have uniformly a deposit of 

 dark yellow felspathic clay, apparently unstratified, and varying 

 in depth from a few feet to 80 feet or more, which is derived 

 from the degradation, and, I think, decomposition in situ, of the 

 clayey sandstones, clay shales, and, especially, the felspathic 



