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Mr. Weaver on the 
pally of black ore, but at greater depths passed into copper pyrites, 
with iron pyrites. The bed of solid ore has varied from one to 
three fathoms in breadth, but thin parallel layers of ore are inter- 
stratified with the adjacent clay slate also to a certain distance. No 
quartz or spars of any kind attend these beds. The more pro- 
ductive parts of the bed have in several instances yielded from ten to 
fifteen tons of merchantable ore from the cubic fathom, the average 
produce of which has varied from five to seven per cent, of copper. 
In some parts of its course, this bed did not produce copper ore till 
nearly at the depth of forty fathoms from the surface, the upper part 
consisting principally of a brown indurated oxide of iron, in which I 
have sought in vain by repeated experiments for the auriferous silver, 
that had occurred in a similar oxide in the upper mine. The bed in 
Tigrony has yielded only iron pyrites. 
§ 111. Beds of iron pyrites, from a few feet to some fathoms 
in thickness, have appeared also in the firm clay slate and quartzy 
clay slate ; as in the deep levels in Tigrony and Cronebane. And 
thin layers and slight threads of copper pyrites and iron pyrites are 
very frequent. Galena and blende have also been met with under 
similar circumstances, but much more rarely; as well as casually 
disseminated in small portions in the beds of copper pyrites, and 
iron pyrites. 
% 112. Several contemporaneous veins of quartz bearing rich 
copper pyrites, accompanied sometimes even by earthy azure copper 
ore, and not unfrequently by chlorite, and whose average produce 
is ten to twelve per cent, of copper, also occur, and more particularly 
in the quartzy clay slate. These veins mostly range and dip with 
the clay slate, ramifying in their extremities through the rock; 
or sometimes coalescing again, they form a considerable body, even 
twelve feet wide of vein, and four or five feet wide of solid ore : but 
