MINERALOGICAL DESCRIPTION OF THE ISLAND OF BANKA, 7B3 
of the ocean at high tide deep and extensive layers of pure clay appear 
in view : they are mostly of a white colour elegantly variegated with 
red, resembling those above mentioned found at the river of Kam- 
p&k and in many other parts of the island. Some portions of the 
general mass are less pure and contain an admixture of minute sili¬ 
ceous particles. Loose fragments of Breccia are likewise strewed 
along the shore, but these appear to have been removed out of their 
natural situation. The usual road between the village of Penjalin 
Belo and R&ng&m passes obliquely over the alluvial range about half 
a mile from the shore : the substances which appear on the surface 
are amygdaloids in fixed veins, from which numerous fragments have 
been detached and strewed in all directions on the road. Their na¬ 
ture is highly diversified. Some are compact, and consist chiefly of 
the substance of the Red-Iron-stone, containing minute particles of 
quartz; in others the particles are large and loosely connected by 
an ochreous cement. 
After a gradual declivity the road enters the stratified district 
which contains the mines of R&ngam, These belong to the kind 
called Kolong or large mines. The stratification of the pit on which 
the workmen had lately been employed was similar to that of the 
mines in the northern district. It consisted of alternate layers of 
sand differently coloured by the intervening clay. The black sub¬ 
stance or clay which almost universally exists in masses in the stra¬ 
tified districts was very abundant, and the constitution of the stra¬ 
tum containing the ore, was explained by the substances remaining 
at the aqueducts. I noticed and collected the following: 
1. Imperfect granite (granitello of Saussure) consisting exclusive¬ 
ly of quartz and schorl; the latter collected in fasciculae made up of 
many needle shaped crystals : the stone is generally of a loose tex¬ 
ture and in a state of incipient decomposition. 
2. The same substance containing felspar which is decomposed 
and appears on the fracture as white clay. 
3. Perfect granite in a state of decomposition s resembling n 
clayey mass in which quartz and mica are imbedded, 
4. Irregular masses of pure quartz. 
5. Pure quartz crystallized. 
6. Vaiiegated mixture of quartz and felspar resembling the same 
substance found at the aqueducts of the mines of the northern divi¬ 
sion. 
7. Felspar in small masses rounded by attrition. 
