710 MIN ERA LOGICAL DESCRIPTION OF THE ISLAND OF BANKA. 
consisted of alternate bands of sand of different colours: there was 
something* singular in the appearance of these strata, which exhibi¬ 
ted strikingly the agitation of water at the period of stratification. 
No Breccias were observed in the environs, nor had any remained 
at the aqueducts after the washing of the ore. 
The contents of the last stratum of the pit lately worked were 
still accumulated and .afforded me an opportunity of examining the 
substances separately and of collecting explanatory specimens. There 
was a striking peculiarity in every thing found at this mine; the 
operation of a powerful cause which is evident in the arrange¬ 
ment of the superior strata shews itself here in the effect produced 
on the separate fragments composing the last layer which contains 
the ore of tin. These substances are almost purely siliceous, com¬ 
posed of quartz, felspar, mica and schorl: among which are found 
occasionally masses of clay, hut they appear to have been subjected 
to a power, which in many cases has completely dissolved their uni¬ 
on or the adhesion of their particles : most of them are so loose in 
their texture that they cannot be handled, but separate and crumble 
to pieces when one endeavours to take them up ; others still retain 
some adhesion, hut the fracture shews a greater readiness to separa¬ 
tion then is generally observed in the stones remaining at the aque¬ 
ducts. In a few the external surface has remained partially entire, 
these are completely rounded by attrition. The regularly striated 
surface which appears on some of the fragments is highly character¬ 
istic of their original constitution, the particles^ of quartz have re¬ 
mained and shew themselves on the strife while the felspar separates 
as a white powder. In some fragments the crystallization of the 
particles of quartz is very regular and these approach the nature of 
rock-crystal: others again consist of minute slender crystals, which 
break when the least force is applied, presenting a fracture covered 
with numerous needle-shaped points; many of the fragments pos¬ 
sessing more solidity, have rounded angles, and their surface marked 
with numerous intersecting lines shews them to belong to those si¬ 
liceous rocks which have already been noticed as occurring in ex¬ 
tensive veins in different parts of the island. 
The white friable substance, found at the termination of the stra¬ 
tum, was copiously dispersed through the heap, and to this the par¬ 
ticles of tin-ore mostly adhered. 
The situation of this mine is about two miles from the eastern 
shore of the island and one from the northern extremity of the 
