BLACK SANDS OF PARACALE. 2AT 
TABLE XXIX.—Direct cyanidation test. Lot No. 2. 
(Ore tube-milled. Heads assay 110 pesos per ton.) 
| Con- 
7 sump- 
MextyNos| sso" || Times libata ‘tion KCN 
of ore. 
Pesos. Hours. | Per cent.| Pounds. 
1 95. 10 1 13.6 0.06 | 
2 95. 10 2 13.6 0. 06 
3 89.00 5 19.1 0.10 |} 
4 78. 50 8.5 28.6 0. 40 
5 65. 20 24 40.8 2.40 
6 57. 40 30 47.6 2.30 
7 23.20 50 78.8 6.8 
8 29. 60 74 74.7 4.2 
9 23.20 96 78.8 4.8 
10 23.20 98 78.8 4.8 
® Calculated from solution assays. 
The screen test of the product is given as follows: 
TABLE XXX.—Screen test. Lot No. 2 after tube-milling. 
Product. Weight. | Weight. 
————ed 
. | Per cent. 
0.39 
0. 62 
1.95 
4.68 
92.38 | 
100. 00 
In these tests the ore was tube-milled for six hours, and as 
shown by the screen analysis of Table XXX, 92.38 per cent 
passes 150-mesh. A sample weighing 1,470 grams was agitated 
in a small Pachuca tank using compressed air. At the beginning, 
the solution had a strength of 0.24 per cent KCN, and after 
ninety-eight hours the strength was 0.16 per cent KCN. The 
pulp had a thickness of 3 parts of solution to 1 part of dry ore, 
and about 5 pounds of lime per ton of ore were added. Samples 
were taken by dipping, and the results of the tailings assays 
were checked by solution assay. It was noticed in taking these 
samples that the heavier minerals tended to concentrate near the 
bottom of the apparatus and so could not be caught in the 
sample. This produced not only imperfect sampling, but inef- 
ficient agitation as well. The assays of the tailings unmistak- 
ably revealed improper sampling, as after one hour the tailings 
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