706 31INERAL0GICAL DESCRIPTION OP THE ISLAND OF BANKA. 
In a valley in a different direction from the stockade, which trans¬ 
mits a small branch discharging’ itself into the large river, these ap¬ 
pearances were still more evident and instructive. The descent 
about 30 feet, is very steep : at the bottom, near the banks of the 
rivulet, I found an extensive vein of Red-Iron-stone. Its surface 
is very uneven and covered with excavation and cellulosities by the 
occasional operation of the water to which it is exposed. The ad¬ 
hesion of its particles is not strong; it is spungy and absorbs the 
water, but acquires more consistence by drying. The fracture re¬ 
sembles that of an earthy mass ; if force is applied the rock breaks 
into irregular fragments, and presents a variegated substance, cellu- 
lous or spongy, consisting of particles of an ochreous nature and col¬ 
our from dark brown to yellow. Black spots possessing nearly a 
metallic lustre are likewise perceptible. 
A peculiarity of this Red-Iron-stone is its being very copiously 
Interspersed with minute particles very lustrous, somewhat resem¬ 
bling mica, but exhibiting an appearance more truly metallic, as 
small folise or squares. 
The side of the hill on this descent presents the strata of which it 
is composed very distinctly. I noticed the following : 
1. Soil. 
2. Sand mixed with fragments of coarse quartz. 
3. Clay with large fragment of quartz and felspar, resembling 
those that are found at the aqueducts of the mines. The most care¬ 
ful comparison with those that were taken up at the mines of both 
peninsulas above described, several months after they were collected, 
shows no difference in their nature or appearance. 
The siliceous portions are pure quartz, or a variegated mixture of 
quartz and felspar, their fracture and mode of separation agrees 
with that of the objects already described ; some fragments consist of 
minute particles of quartz regularly crystallized bedded in felspar 
which is decomposed and appears as a white powder. The separat¬ 
ed particles of the [jure felspar are rhombs, prisms See. 
Those layers in which the clay was more abundant, both in this 
valley and on the ascent of the hill above mentioned, equally agree 
with those observed at the mines; the clay is mostly of a white co¬ 
lour, and contains minute siliceous particles of the nature of the 
larger ones. 
The compact Red-Iron-stone was found in detached fragments 
not only near the banks of the river, as mentioned above, but in va- 
