OCCURRENCE OP COPPER ORE. 237 



hydrated carbonate of copper, is comparatively rich in metal, as the 

 copper in pure samples exceeds 57^ per cent. 



4. Results of Assays. — A small sample shewing faint stains, from 

 the face of the outcrop, yielded in metallic copper only 0-21 per cent. 

 Another sample, also from the face of the outcrop, but containing small 

 specks of earthy malachite, jaelded 0'73 per cent. A sample taken 

 from about twelve feet from the edge of the outcrop, and weighing 

 nearly five pounds, gave 986 per cent. Two other samples gave 

 respectively 4-63 and 6-15 per cent. Finally, a small sample from the 

 same place, containing numerous strings of copper glance, yielded no 

 less than 22-16 per cent. A piece of rock of about half a pound 

 weight, picked up on the shore about a mile from the excavation which 

 furnished the above samples, gave 4.58 per cent, metallic copper. 

 Discarding the very rich and the very poor specimens, as exceptional 

 examples, the results of these assays indicate an average yield of rather 

 more than 6 per cent. But with the exception of the sample found 

 upon the shore — and this may have been rolled .there by the set of the 

 tide, or dropped by some one passing the spot — these samples, it must 

 be remembered, were obtained from a single spot of very limited extent, 

 and hence they may not indicate in any way the true yield of the entire 

 bed. 



If the ore, allowing for loss, average 5 per cent, metal, each cubic 

 fathom will contain about 2,020 lbs. of copper, and will weigh about 

 eighteen English tons. Taking the mean thickness of the bed at only 

 six feet, and assuming it to extend eastward, with the same yield of 

 metal, to a distance of ten fathoms only, each mile in length will com- 

 prise 8,800 cubic fathoms of copper-holding rock, and will carry 7,890 

 tons of metal, worth, at the present low price of copper, about £580,000. 

 In reference to this calculation, however, it must be observed that 

 although the bed will probably be found to extend eastwards to a much 

 greater distance than ten fathoms, its richness may not be constant 

 throughout that distance ; nor may the assumed yield be found to hold 

 good, from fathom to fathom, along the entire length of the bed. On 

 the other hand, the small strings of copper glance, as seen in the sam- 

 ples hitherto obtained, may thicken and form a network of ramifying 

 veins, running in a general north and south direction — and in that 

 (i,ase, the returns would be greatly in excess of the above estimate. It 

 will thus be seen that in the present undeveloped state of the deposit, 

 no definite conclusion can be arrived at respecting its true value. 



