MINERALOGICAL DESCRIPTION OF THE ISLAND OF BANKA. 7^7 
above been noticed. They were generally very ponderous and indi¬ 
cated the presence ot much Iron. 
The mountain Gunong M&ngkul is very distinctly observed from 
the naked spots of this mine, it is a long extended ridge following 
the general direction of the island, and intersected by several deep 
vallies, the further south-east extremity is called Gunong Ladi. It 
consists of granite, rocks of which are also found in the surrouning 
tracts. In the fragments which I examined the quartz and felspar 
are equally distributed the latter often has a reddish tinge ; the mi¬ 
ca is more abundant than in many other granites of Baqka. 
In a direction south-west of the mines of Bakung the country is 
slightly variegated by inconsiderable elevations; many tracts are low 
and appear to be occasionally inundated, numerous rivulets pass 
through them. Vegetation is very abundant and the soil a deep 
black mould, occasionally some loose Red-Iron-stones are observed 
on the road. 
As I approached Tirak I passed several mines none of which 
were worked at this time; near the stockade I found numerous 
remains of former mines, and as their examination terminated my 
mineralogical remarks in this part of the island, the most southern 
that I visited, I shall carefully enumerate the substances I observed 
and collected, in order to shew, as far as my observations extended, 
their generality on Banka. 
1. A fragment of granite apparently taken from the strata of 
the mines : the felspar is in a state of incipient decomposition, the 
whole mass shews a disposition to separate, the surface being burst 
in many places: most of the mica has crumbled away, and only ve¬ 
ry minute particles are observed scattered on the surface. 
2. A fragment consisting of crystals of quartz semi-transparent, 
the intervening felspar appearing on the fracture as a white friable 
powder. 
3. Variegated siliceous masses consisting of quartz and felspar 
nearly equally distributed. 
4. Rhomboidal fragments consisting almost of pure felspar. 
5. Sandstone of a fine grain with acute angles and regular sides. 
6. Red-Iron-stone very ponderous, the fracture exhibiting nu¬ 
merous nodules inclosed by thin laminae, often double and concen¬ 
tric, containing earthy particles: the insterstices between the no¬ 
dules are filled up by a dark coloured substance possessing a partial 
lustre. 
