244A FANNING AND EDDINGFIELD. 
small for practical consideration. A Huntington mill will prob- 
ably do no better on such a concentrate, and in all probability its 
work will be nearer the result indicated by numbers 1 and 2 
rather than 3 and 4. 
The tests indicate that the treatment of the concentrates by 
amalgamation is unsatisfactory unless the product is tube-milled. 
When this is done a fair extraction may be expected. 
CYANIDATION TESTS. 
The attention of metallurgists has been directed within recent 
years to the cyanidation of mill concentrates, and several plants 
are now in operation, such as the Goldfield Consolidated and Alas- 
ka-Treadwell mills, where the success of this phase of cyanide 
treatment has been fully demonstrated. It has generally been 
found that the essential features of such treatment are fine 
grinding, agitation, and considerable time, although there is a 
wide range of variation depending upon the nature of the ore. 
We have investigated the possibility of cyaniding the concen- 
trates from the dredge, and it is possible that these tests are the 
first which have been published on this treatment applied to 
such a product. In consideration of the number of dredges 
which are saving black sands in their cleanups, it would be well 
if this method of treatment were given a thorough investigation 
in other parts of the world. The results obtained were so 
highly successful as to lead to the belief that many dredges, now 
throwing away large quantities of low grade concentrates, could 
cyanide these with considerable profit. 
Cyanidation tests on lot No. 1.—A preliminary cyanide test 
was made on an original sample of lot 1, and it was found that 
25 per cent of the gold could be recovered in twenty-four hours 
using agitation with 0.26 per cent potassium cyanide (KCN) 
solution and a ratio of solution to ore of 1:1. The consumption of 
cyanide was 450 grams (1 pound) per ton of ore. This test in- 
dicated that ordinary leaching is of little benefit, a fact con- 
firmed by the coarseness of the free gold and the impenetrability 
of the mineral crystals. 
A sample of lot 1 was then tube-milled for six hours, and the 
screen test showed 98 per cent passing 150-mesh. The product 
was then divided into 2 sections, one for amalgamation and 
subsequent cyanide treatment, the other for direct cyanide treat- 
ment. As shown by the following tables, the total extraction 
is exceedingly high where amalgamation is used previous to 
