COLLECTIONS IN ECONOMIC GEOLOGY AND METALLURGY. 8? 



sides of the mortar, the exit of the crushed material being aided by a 

 stream of water. There will always be some copper in the ore too l;u}j;e 

 to pass the screen, and every 8 hours the stamp is stopped and the cop- 

 per is taken out of the mortar. It is known as " mortar heads." 



It has not been found practical to size the crushed ore by the ordi- 

 nary means, and it is only partially accomplished by hydraulic separa- 

 tors, which are simply long double V shaped troughs in which the ore 

 falls against an ascending current of water. At suitable distances 

 there are holes in the bottom of the inner trough allowing the particles 

 of ore that have settled at different distances in the trough to pass into 

 compartments in the space between the two troughs from whence it is 

 drawn to feed the jigs. The first compartment will contain the coarsest 

 and heaviest of the crushed material, and the second compartment the 

 next coarsest and heaviest, and so on. The rock being quite regular in 

 its shape each compartment will contain grains of about equal size, but 

 the copper, being very irregular in size and shape, varying from spheri- 

 cal or cubical to very flat and thin, will vary much in the size of the 

 grains in any one compartment. The settlings from each compartment 

 are delivered to its own set of jigs by a stream of water. 



The jigs mostly used are known as Collom plunger jigs from the fact 

 that the material on the sieve is kept agitated by a plunger which is 

 alternately forced rapidly down by a rocker striking the end of the pis- 

 ton and is slowly raised by a spring. These jigs yield four classes of 

 products. First, ragging, particles of rock containing a little copper; 

 second, heads, nearly pure copper ; third, hutchwork, a mixture of cop- 

 per and rock material that has passed through the bed of heads on the 

 sieve; fourth, tails. 



The ragging is either returned to the stamps or else treated in special 

 apparatus. The coarse heads are sent to the smelting works, but the 

 finer heads contain considerable rock material and are treated in keeves 

 and buddies. The hutchwork is sent to jigs with finer sieves, the coarse 

 tails are rejigged and the final tails dumped into the lake, while the 

 finer tails are treated in the tail house. 



The slimes that do not settle in the hydraulic separator go to settling 

 boxes, and the settlings from these go through a complicated treatment 

 on slime tables and in keeves and buddies, the final products being 

 finely divided copper containing considerable foreign matter. 



The Osceola stamjj mill. — This mill is situated on the north shore of 

 Portage Lake, affording the necessary supply of water, and a conven- 

 ient dumping ground for refuse material. It is provided with four Ball 

 steam stamps, fifty-four Collom jigs, live Evans slime tables, togetlier 

 with all the necessary adjuncts for carrying on the work successfully. 

 The jig floor is divided into three divisions, each containing a stamp 

 and set of washing apparatus. The fourth stamp is held in reserve, 

 and is arranged to deliver thostanq>ed rock to either one of the three 

 divisions. Each division contains three hydraulic separators, each one 



