410 MINERALOGICAL description of the island of banka. 
crystals of quartz in some places, intervening 
small masses of clay. 2 feet. 
4. Black-clay massive in irregular co-agula. 2 „ 
5. Fine sand, dispersed through particles of quartz and frag¬ 
ments of decomposed granite-rocks : here the ore commenced to be 
thinly disseminated through the stratum, the lowest portion of the 
layer which had been carried out from the last pit adjoining to the 
present work, had consisted of very large fragments of decomposed 
granite, through which the ore had been plentifully dispersed. The 
miners informed me that the vein of ore on which they had been 
employed for 3 years, and which occupied the lowest part of the val¬ 
ley, had several times intersected the course of the river which flows 
through it. 
Of the peculiarities of the stones which I found at the aqueducts 
of this mine 1 shall only enumerate the following. The crystals of 
quartz had mostly a tapering wedge-like form, they were opaque 
though apparently pure in their nature. The felspar separated in 
rhomboidal masses, and was of various shades of colour: some of 
the fragments were very beautiful. I remarked for the first time 
schorl in elegant needle form crystals adhering to the fragments of 
quartz : it was also often combined with quartz to an imperfect gra- 
nitello: the schorl in these cases was distributed through the quartz 
in nearly equal proportions, in small irregularly rhomboidal crystals ; 
the substance of this combination was very loose and friable. 
The amygdaloid , consisting of a mixture of Red-Iron-stone with 
particles of quartz and felspar, in various proportions, so common 
in the mines of the Upper and Lower-furnace and of Klabbet, was 
not found among the stones of the aqueducts of the mines of Sun- 
nie, or it existed to sparingly that it eluded my attentive search. 
The remarks which I made in my further course to the northern- 
coast of Banka, explained this circumstance. The mine of Sunnie, 
as above marked, is situated near the northern boundary of that 
portion of this peninsula, which I have called the district of the 
mines. Several hills, which form an irregular ridge, bound this dis¬ 
trict in the north. The chief of those is called by the natives Gu- 
