The process is itself one of
smelting on a small scale. As might be expected, however, the assay
produce and the smelting produce are not the same, there being a smaller
loss of copper in the smelting. The method has worked very well, but
when applied to the purchase of low class ores (from which the whole of
the copper is extracted by wet methods) it is unsatisfactory. The
following table, which embodies the results of several years' experience
with copper assays, shows the loss of copper on ores of varying produce.
The figures in the fourth column show how rapidly the proportion of
copper lost increases as the percentage of copper in the ore falls below
30 per cent. For material with more than 30 per cent. the proportion
lost is in inverse proportion to the copper present.
LOSS OF COPPER.
-----------------+------------+-----------+------------------
Copper present. | Dry Assay. | Margin. | Loss on 100
| | | Parts of Copper.
-----------------+------------+-----------+------------------
Per cent. | Per cent. | Per cent. |
100 | 98 | 2.0 | 2.0
95 | 92-1/2 | 2.5 | 2.6
90 | 87-3/8 | 2.6 | 2.9
85 | 82-3/8 | 2.
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