* 
68 Rie De Al Jackson on tua i : 
The most common veinstone is Gaaiiies which oceurs in reg- 
ular symmetrical veins, the prehnite encrusting the sides of the. ~ 
fissures and closing in the middle of it by sul da wogenip botryoidal 
surfaces. At the surface these veins are rarely more than six’ 
r, the presence of which in decomposed veins is most read- 
co 
ily detected by spots of green carbonate of copper, derived from 
exposure of the metal to the air and water. These narrow and .~ 
rock, until at last the prehnite gives way to copper and its space 
is entirely occupied by it, a thick vein of solid copper filling the 
ssure, while the prehnite was either absorbed by the _ or the 
épuditian of the rock was such that it could not be form 
At the Cliff Mine of the Boston and Pittsburg Minis Gouna 
ny, the vein at the top of the cliff consisted of prehnite, contain- 
ing only minute scales of copper, and was only six inches wide, 
but it was found on descending that this vein widened, about two 
hundred feet lower down, to ‘eighteen inches, and lower still it 
had widened to two feet, and was charged with from five to thirty 
per cent. of metallic copper, and some particles of silver. The 
average yield of a large sample of the vein at the surface was 
found to be 5,°;th per cent. of copper, and it was estimated that 
the ore could be practically “ bucked” or picked up to 15 per cent. 
The width of the vein was estimated to be three feet at the 
base of the hill, where it was still concealed from view by the 
soil. On driving a level into the cliff and one at the base of the 
hill, the vein was proved to be much richer than at the surface, 
and on sinking a shaft to the depth of 226 feet below the base 
of the hill, it exposed sheets of copper varying in thickness from 
a few inches to three feet. These masses of copper filled the 
vein, and the prehnite and other zeolitic minerals disappeared. By 
earrying forward levels at the proper points, sixty feet below each 
other, and by stoping out the backs of the levels, large flattened 
ellipsoidal masses of copper were exposed, and removed by heavy 
blasts of gunpowder. ‘These masses were then cut up by mor- 
tising out channels through them by means of steel chisels, driven 
by a heavy sledge hammer. 
Some idea may be formed of the rapid increase in srs of 
this lode by comparing the poor prehnite vein at the top of the 
hill with the ponderous masses of pure copper ion are now cut 
up in the mine below. Oue mass of pure copper extracted while 
I was on the survey, weighed eighty tons, and other masses prob- 
ably of equal magnitude were in process of being uncovered. 
‘Taking into accouut the height of the cliff in which the vein 
is seen, and the depth of the shafts at its base, we have the vein 
proved 526 feet deep, and thus far it has been steadily enriching, 
and has surpassed the most sanguine expectations of all the miners 
and geologists who had examined it. 
