930 FANNING AND EDDINGFIELD. 
MAGNETIC SEPARATION. 
The magnetic treatment of the middlings, as performed in 
the panning tests, just described, showed the marked association 
of the gold with the nonmagnetic material. It seemed apparent 
that if the original product were treated magnetically we could 
obtain a nonmagnetic product containing a large percentage of 
the gold. Accordingly a sample of lot 2 was magnetically 
treated and gave the following results: 
TABLE XIII.— Magnetic separation test. Lot No. 2." 
| . . Assay | Gold distribution 
Product. Weight. | Weight. per ton. jin 1 ton of original. 
| Grams. | Per cent.| Pesos. Pesos. Pe cent. 
Original ==. = 2.622.225. oe = 3,69) |2-222---2 102.70 102. 70 
Nonmagnetic______-----__--_-- 2, 100 68.3 170. 40 99. 50 
Magnetic 2-27-08 3522. eee 1,495 41.7 7.50 3.20 
97.21 
2.79 
The separations were made by means of a small electro-magnet moved 
by hand over the ore spread in a thin layer on a sheet of paper. This 
method does not actually represent the work of machines such as the 
Wetherhill and Ding, but it gives an approximate idea of the weights and 
values of the products. The magnet has a core 20 centimeters long with 
a diameter of 2.5 centimeters, and is wound with about 1,000 turns of No. 
19 copper wire, B. and S. gauge. A current of 1.5 amperes and 107.5 
volts was used in all tests. After picking up the magnetic material, the 
magnet was moved to a second sheet of paper where the product was drop- 
ped, spread out, and the magnetic minerals again picked up. The necessity 
of this second treatment lies in the tendency of the gold to be picked up 
with the magnetite in the first treatment. When sized products were used, 
this tendency practically disappeared, although with moist samples it still 
would be a serious consideration. 
8 Ratio of nonmagnetic to magnetic—1.7 to 1. 
If 100 tons of concentrates worth 102.70 pesos per ton were 
treated magnetically, we could obtain 58.3 tons of nonmagnetic 
product worth 170.40 pesos per ton and representing an extrac- 
tion of 97.21 per cent. 
In order to study the association of the gold with the non- 
magnetic material, a sample of lot 1 was screened through a 
series of meshes, and each screen product was separately amal- 
gamated and then magnetically treated. This clearly shows (1) 
amalgamable free gold on each mesh, (2) gold associated with 
the nonmagnetic portion, and (3) gold associated with the 
magnetic portion. The results are given in Table XIV. 
