406 MINERALOGICAL DESCRIPTION OF THE ISLAND OF BANKA. 
ore were still found adhering, and irregular fragments and crystals 
of pure quartz of various shades of colour. 
In proceeding from the district of the Lower to the Upper-furnace 
one perceives, on the road, the vestiges of many of the old mines ; 
they form a contrast, though by no means a pleasant one, with the 
abundant vegetation of the Island : the places of the small mines pre¬ 
sent a naked uneven surface, covered with the remains of the former 
works, to which the shining particles of quartz mixed with the sand 
impart a peculiar aridity: the place of the large mines is known by 
extensive chasms alternating with irregular hillocks. It requires 
however, but a short time in Banka, to cover the whole with fresh 
vegetation, and in a few years the spots where the mines were work¬ 
ed are converted again into forests. 
The mine of Simgei-Tdngo , is the most important of those of the 
Upper-furnace ; it employs more workmen than any other single mine 
on the Island, and produces, in one season, more metal. The stra¬ 
tification of the excavation is very regular: it consists, under the soil* 
of alternate layers of sand and clay of various colours, between which 
the Black-clay occurs in extensive irregular masses. The lowest 
stratum, containing the ore, had been lately carried out, and was col¬ 
lected in a large heap preparatory to the process of washing. 
I collected at this heap a great variety of the stones which had 
composed the stratum of which I shall only mention the chief, as the 
other varieties will be successively pointed out in the description of 
the mines. 
J. Quartz, regularly crystallized but opaque. 
2. Felspar in irregular rhomboidal fragments, mostly with flat 
sides arid sharp angles, pure, or mixed with minute particles of quartz. 
3. Felspar and quartz alternating in nearly regular strata, or 
disposed so as to produce a marbled (variegated) surface: often in 
fragments of considerable size. 
4. Pure quartz, massive. 
5. A lamellated stone consisting of minute crystals of quartz, 
united to a friable mass with regular surfaces. 
6. Quartz and felspar mixed nearly in equal proportion, the 
