|
TITE MINING AND MILLING PEACTICE.
|
115
|
||
|
|
|||
|
reservoir that furnishes the giant at the mine, by an 18-inch spiral riveted pipe-line, 2880 feet in length, under a head of 226 feet. The weight of the stamps is 450 pounds; drop 9 inches, 80 times per minute; discharge 2 inches; round punched screen, 120 holes to the square inch; length of plates (plain copper) 8 feet in two sections; ten of the stamps were fitted with silvered plates in 2-foot sections. Only the upper 4 feet of the plates in the mill are kept in shape; it is stated that no gold was saved on the lower ones. The tailings flow off through mercury traps. The overflow from both the outside and inside bins runs through a short line of riffled sluice boxes. At the time of our examination seven men were employed in the mill in two shifts, at 90 cents per day.
THE LOCKHART MINE, LUMPKIN COUNTY, GA.
The Lockhart mine is situated on the west bank of the Yahoola river near Dahlonega, Ga. It represents the working of ore-bodies of the Dahlonega type by underground mining.
The Dahlonega method of mining the saprolites was formerly employed here, and the old open cuts, now practically abandoned, are of considerable extent. This is the only mine in the Dahlonega district where underground work of any importance has been carried on. The ore-bodies consist of veins of the Dahlonega type (see description, pp. 22 and 23) where the quartz-filling has been more extensive, in places occupying the greater part of the fractured gneiss bands, which in a mining sense may be termed the vein, the boundaries of the gneiss bands forming continuous, smooth walls, and being the limit of the mineable ore. The normal strike of the schists at the Lockhart is northeast and the dip southeast; at one point, however, the schists bend around a mass of " brickbat," the strike being abruptly changed to the northwest and the dip to the northeast.
The principal work has been done on the Blackmore vein, where the country is a biotite hornblende-gneiss. The strike of this vein is 1ST.E. and the dip 30°-60° S.E. It varies in thickness from 3 to 6 feet. The orebody is opened by two adit-levels on the vein, 60 feet apart. The lower one, which enters the hillside at a depth of about 135 feet below the original outcrop, has a length of 400 feet, and the ore has been stoped out between it and the upper level for a distance of 100 feet from the face, which is the length of the ore-shoot so far as explored. This shoot has also been worked from the upper level to the surface. The pitch is steeply to the N.E. The ores from this shoot mill from $4 to $5 per ton. Besides this richer shoot the bottom level exposes ore throughout its entire length. This, however, decreases in quality as the mouth of the tunnel is approached, where it yields only $1. The system of work is underhand stoping, stulls being placed 6 feet apart to hold
|
|||
|
|
|||