BLACK SANDS OF PARACALE. 251 
Other practises are described by Crosse,!? Treatment of Ore 
Slime; Lindlay,** Notes on the Treatment of Mill Concentrate; 
and others. 
GENERAL COMMERCIAL CONCLUSIONS. 
The assays of the black sands have shown that a great loss 
of gold is taking place. The concentrates from the cleanup 
have a value which would pay for their cost of shipment many 
times over. Even after the most careful cleaning by the dredge, 
these concentrates frequently assay better than 100 pesos per 
ton. 
A greater saving of the black sands can be made by more 
frequent cleanups. This also would result in a greater saving of 
the fine gold. Owing to the present arrangement of the tables, 
it is imposible to make a complete cleanup ,without shutting down 
the dredge. Some of the California dredges * have used a sys- 
_ tem by which the gravel is diverted to some of the tables, thus 
permitting a cleanup while in operation. 
The present dredge does not utilize the full table area, and 
there is the possibility that another style of riffle would prove 
more effective in saving not only a large amount of the sands, 
but more of the fine gold as well. Powell '* has recommended the 
carabou riffle as being very efficient. 
Brazenall ** has advocated the use of the Hancock jig to treat 
the dredge tailings of fine mesh. However, since the date of his 
writing, the Richards pulsator jig 1” has been placed upon the 
market and is in successful operation in many mills. The ad- 
vantages of the Richards jig are: (1) Extremely small size, (2) 
very small power required, (3) small weight, and (4) small 
amount of water used. The possibilities of this jig, probably in 
combination with Wilfley tables, should be investigated. 
Richards 1® has described a dredge having the following pro- 
cess: (1) Sereen, (2) 30 coco-matting tables, (3) Wilfley tables, 
(4) amalgamation plates, (5) amalgamation cleanup barrel, (6) 
classifier, (7) amalgamation plates and traps, and (8) Wilfley 
* Journ. Chem. Met. & Min. Soc. So. Af. (1909), 10, 172. 
*Tbid. (1911), 12, 2 and 228. 
* Aubury, Bull. California State Min. Bur. (1910), No. 57, 79. 
* Eng. & Min. Journ. (1903), 83, 251. 
* Eng. & Min. Journ. (1907), 83, 918. 
“ Shepard, Eng. & Min. Journ. (1909), 87, 545. 
** Richards, Ore-dressing. New York (1906), 4, 1655. 
