MINERALOGICAL DESCRIPTION OF THE ISLAND OF BANKA. 713 
tract which transmits the large river of Layang : one arm of this 
ridge, the mountain Puwak above mentioned, extends eastward form¬ 
ing Tanjong Raya, its continuation to the south I followed and met 
at different points. Leaving the northern hills the road proceeds 
close to the east side of the mountain Bettung for several miles and 
then diverges towards the mines of Robo-kli . 
Large rocks of granite cover the separate hills, as well as the 
sides of the large mountain ; here the piles are uncommonly large, 
precipitous or widely rounded resembling both in fracture nnd com¬ 
ponents parts those found on the tract from Klabbet to Mamp&ng : 
the only obvious difference I remarked was less regularity in the dis¬ 
tribution of the felspar. These granite rocks extend to the neigh¬ 
bourhood of Robo-kli. 
The strata of the mines of this district, which from the remains 
on the surface appear to have been very extensive, are undoubtedly 
in conjunction with those which I examined on the road to Robo. 
Many of tjie explanatory specimens I collected were of the same 
kind. The rock, consisting of regular crystals united by a cement 
of clay, was very abundant, also pure rock crystals, and the earthy 
substance found in the strata which resembles granite, in a state of 
decomposition. These I met with in the exhausted mines. Here 
the Red-Iron-stone was also copiously found and particularly that 
variety which I have called Breccia or Amygdaloid. Large quan¬ 
tities have been brought up by the miners, some appear to have 
been found in immediate conjunction, others have doubtless been 
situated very near the primitive rocks. Several of the fragments 
which I collected here are of a mixed nature, they consist partly of 
the crystallized siliceous rock above described and of particles of 
Red-Iron-stone either entire or in a state of decomposition. One 
of my specimens is highly characteristic and show r s also in this part 
of the Island the conjunction of the primitive rocks with the Red- 
Iron-stone or Breccias. In various parts of the further track to 
Marawang I found loose fragments of this stone on a surface of 
sand. 
Those mines of Robo-kli which are at present worked, are of 
tuated above a mile to the east of the road on which the stockade is- 
the miners is constructed. On my way thither I passed several large 
granite rocks. The strata, following the soil, consisted of clay, clay 
and sand mixed, or sand distributed through fragments of Red-Iron 
stone. Some of the clay which remained from the last works was 
