712 MINERALOGICAL DESCRIPTION OF THE ISLAND OF BANKA. 
In one of the mines in which the workmen were at this time em¬ 
ployed, the ore is found but a few feet below the surface. Under 
the soil I remarked a layer of white clay containing siliceous parti¬ 
cles. It often separated in large masses which had greatly the ap¬ 
pearance of the granite of the neighbouring hills in a state of com¬ 
plete decomposition ; particle of mica and schorl were distinctly per¬ 
ceived in it. Among the stones at the aqueducts were some silice¬ 
ous fragments of considerable size, several of these resembled the 
stones found at Wunhin, but they had generally more consistence. 
The fragments of felspar had mostly rounded angles, some were 
botryotdal and the colour of all was white or yellow. Fragments 
of Breccia were very sparingly distributed. 
The last mine which I examined at Robo was near the eastern 
boundary of the island ; the ore is here found within half a mile from 
the ocean. The stratum commences immediately under the soil and 
extends on an average to a depth of ten feet; it consists of sand of a 
dirty yellow and grey colour, through which the ore is thinly dis¬ 
tributed t it is not perceptible to the bare eye. 
This stratum contained comparatively few large fragments, and 
those which I found were mostly anomolous in their nature. The 
siliceous fragments w r ere generally of a deep blue colour, a few were 
white, and some regular rock-crystals also occurred, besides these 
I found: 
]. A fine grained sandstone intersected with regular lines. 
2. A coarses grained sand-stone. 
3. Small fragments of amygdaloids in th|n plates different both 
in colour and consistence from the common breccias. 
4. A pecies of slate, differing from common slate only by a 
greater degree of hardness : its fracture, colour and streak are the 
same. I have not found this species of stone in its original situa¬ 
tion or in fixed veins, and I cannot therefore trace it to its origin. 
This was the only mine in which I found it. The place where the 
kind of sand-stone here mentioned exists in extensive veins and 
rocks will be pointed out in the sequel. All the substances occurring 
at this mine exhibit the appearance of having been carried hither 
from a considerable distance. 
On the course fr<&m Sungie-Mt to Mardwang I passed between 
two separate promontories of the mountain Bettung, stretching se¬ 
veral miles to the north. This hill continues the primitive ridge 
from the district of Belinyu (and Lumut) south of the low alluvial 
