708 MlNJiRALOGICAL DESCRIPTION OF THE ISLAND OF BANKA* 
The sides were externally in most cases flat or tabular, but the sur¬ 
face was grooved or pitted. Those fragments which were separated 
from the common pile had generally on oblique disposition. The ge¬ 
neral colour of the rocks externally was grey, but they were varie¬ 
gated with narrow streaks or lines, formed by a substance different 
from the common rock, and often crossing eacli other in a manner 
similar to those above described found in the river of Katnpak ; at 
these lines they separated into rhomboidal and pyramidal fragments, 
of great variety. The colour of the fracture was light blue or white, 
and lines of a different colour were observed on it as on the surface. 
The substance of the rocks was purely siliceous and exhibited not 
the least sensibility on the application of the strong acids. Frag¬ 
ments of the same kind of stone were brought to me by the natives 
from the declivities of the mountain Penyabong, possessing the same 
colour, fracture, disposition to separate &c., the similarity, in one 
respect, of the rocks in the river of Kampak has already been men¬ 
tioned, and similar rocks were afterwards found in the environs of 
Minto. This rock deserves some notice in the mineralogy of Ban¬ 
ka, its nature approaches to that of Hornblende ; but I shall not, at 
present, give it specific name ; is probably beio gs to the class of 
Primitive trap of Werner. Its fracture considerably resembles that 
of Basalt. 
This pile is placed in some degree intermediate between the se¬ 
condary district (or that consisting of Red-Iron-stone and of various 
strata) and the primitive ridges which traverse the eastern bounda- 
dary of the peninsula. From the mouth of the river of Layang to 
the mines of Katta the country is but little raised above the level of 
the ocean. Near the mines of Katta and further eastward the coun¬ 
try gradually rises: it is connected with the district containing the 
mines of Mapur and Dsheniang above mentioned, stretching thence 
in a southern direction to the extremity of the island. This tract 
comprises the mines of Sungie-liat, Marawang and Pangkal-pinang. 
Although the same substances found in the parts of the island al¬ 
ready described constantly occur again, there are peculiarities in 
the arrangement of the strata, and in the component parts, of which 
I shall endeavour to give an account in the continuation of the mi- 
neralogical details. 
The chief mines of the district of Sungie-liat, (besides those of 
Katta and Dsheniang already mentioned) are those of Lam pur, Ayer 
Dunn, Robo arid Robo-kli : the former two are situated westward, 
