BLACK SANDS OF PARACALE. QA5 
cyanidation and a high extraction can be obtained without amal- 
gamation when sufficient time is given to dissolve the gold. 
TABLE XXVII.—Cyanidation tests. Lot No. 1." 
(Ore was tube-milled ; 98 per cent passed 150-mesh.) 
Assay |mxtrac-| Assa 
| Fi - y |Extrac- . Con- 
ji Assay ee tion by |of tails| tion by| Total |Strength eeu) sumption 
No, | Weight) of heads|.- jig,.| amal- | after | cyani- | extrac-| of KCN |~;:,,, | of KON | Time. 
= per ton. eas gama- |cyani-| dation! tion. | solution. to ore.| P&E ton 
*| tion. |dation.| alone. re- | of ore. 
per ton. 
Grams.| Pesos. | Pesos. | Per ct.| Pesos.) Per ct.| Per ct.| Per ct. Pounds. |Hours. 
1 120 | 299.50] 120.70 59.8} 3.80 96.8 98.8 0.29 Seat 1.0 48 
2]. 120] 299.50) 120.70 59.8 | 3.00 97.4 99.1 0.29 3:1 2.0 96 
3 120 | 299.50 Gyn |e oes 60. 40 79.9 79.9 0.28 3:1 3.0 24 
4 120 | 299.50 (6)5 Gites eS 6.20 98.0 98.0 0. 23 321 10.4 96 
= Jn these tests, the ore was agitated in a bottle and about 2 kilograms (4 pounds) of lime 
per ton of ore were added. 
> Cyanided direct. 
As shown by tests 1 and 2 of Table XXVII, the highest ex- 
traction is obtained by cyanidation when preceded by amalga- 
mation. Where this is done, a total extraction of 98.8 per cent 
is obtained in forty-eight hours. By doubling the time of agi- 
tation, the extraction is increased only 0.3 per cent. The low 
cyanide consumption is particularly to be noted, and it is evident 
that the ore contains few or no minerals injurious to cyanide 
solutions. 
As shown by tests 3 and 4 of the same table, an extraction of 
98 per cent can be obtained without previous amalgamation, 
the essential requirement being time, for in twenty-four hours 
the extraction was only 79.9 per cent, whereas in ninety-six hours 
the extraction increased to 98 per cent. It is to be noted that 
the consumption of cyanide is larger in tests 3 and 4 where 
amalgamation was not used, and this to some extent is due to 
the greater amount of gold actually dissolved. 
The presence of a large amount of coarse gold in lot 1 has 
been repeatedly mentioned and it would naturally be expected 
that cyanidation would be very ineffective on such gold. It is 
undoubtedly necessary either to remove this gold by amalga- 
mation or to break it up by fine grinding. The gold evidently is 
in such form as to be broken up by erdinary tube-milling, for, 
upon screening the tube-milled product through 100-mesh, no 
pellets were found and only a few flakes were revealed on the 
150-mesh screen. This brittle feature of the gold applies to 
118321——3 
> 
