| Arsenic | Antimony | Bismuth | Iron | ||
|---|---|---|---|---|---|
| 1. | Electrolytic conductivity copper, | 0·016 | trace | nil | 0·042 |
| 2. | Lake copper, | nil | trace | nil | 0·0077 |
| 3. | Best select copper, | 0·025 | trace | 0·011 | 0·10 |
| 4. | Tough pitch copper, | 0·320 | trace | 0·010 | 0·010 |
| 0·0211 | 0·630 | 0·0044 | .. | ||
| 5. | Copper fire-box plate | ||||
| (ran 500,000 miles, Met. Ry.), | 0·3726 | 0·0346 | 0·0360 | 0·0069 | |
Intermediate Products— | |||||
| Refined converter copper, | 0·0211 | 0·0630 | 0·0044 | .. | |
| 0·0290 | 0·0254 | 0·0035 | trace | ||
| Cathode copper, | 0·00034 | 0·0008 | 0·0003 | .. | |
| Black copper, | trace | .. | .. | .. | |
| 0·052 | 0·2380 | 0·0035 | 0·17 | ||
| Cement copper (Spanish), | 2·95 | 0·50 | 0·95 | 7·00 | |
| 1·32 | 0·02 | .. | 7·6 | ||
| Blister copper, | 0·108 | 0·157 | 0·055 | 0·4 | |
| Chili bar, | 0·100 | trace | nil | 0·009 | |
| Nickel | Tin | Oxygen | Sulphur | ||
|---|---|---|---|---|---|
| 1. | Electrolytic conductivity copper, | 0·006 | .. | 0·008 | nil |
| 2. | Lake copper, | 0·0146 | nil | 0·070 | .. |
| 3. | Best select copper, | 0·061 | .. | 0·143 | .. |
| 4. | Tough pitch copper, | 0·060 | .. | 0·120 | .. |
| .. | .. | 0·284 | .. | ||
| 5. | Copper fire-box plate | ||||
| (ran 500,000 miles, Met. Ry.), | 0·3039 | .. | 0·0181 | 0·0064 | |
Intermediate Products— | |||||
| Refined converter copper, | .. | .. | 0·284 | .. | |
| .. | .. | 0·12 | 0·01 | ||
| Cathode copper, | .. | .. | 0·005 | .. | |
| Black copper, | 2·04 | 0·07 | .. | 0·80 | |
| .. | .. | .. | 0·796 | ||
| Cement copper (Spanish), | .. | .. | 16·00 | 5·10 | |
| .. | .. | .. | 0·48 | ||
| Blister copper, | 0·0–0·2 | 0·0–0·5 | .. | 0·112 | |
| Chili bar, | .. | .. | .. | 0·909 | |
(2) Sulphide ores supply the bulk of the world’s copper, constituting upwards of 80 per cent. of the total.
(3) The oxidised ores are found in most copper districts, though usually to only a limited extent. They are often gossan deposits produced by weathering or by decomposition of sulphides, hence are generally found nearer the surface, changing to sulphide with depth. The supply of copper from oxidised ores, which was at one time very large, is decreasing rapidly, and the greater proportion of the copper now obtained from them comes from the more recently developed deposits, of which those at Tanganyika afford an example.
More than 200 minerals which contain copper are known, but most of them are unimportant from the smelting point of view. The characteristics of the more noteworthy may be fully studied from text-books of economic mineralogy.
Copper Ores—Native Copper.—Occurs extensively in the Lake Superior district of Michigan, in Precambrian rocks, sparingly in New Mexico and China, but seldom anywhere else in workable quantities by itself. Copper barilla or copper sand, an impure native metal from Chili, was formerly of importance. Native copper constitutes about 20 per cent. of the North American supply. It yields metal of exceptional purity, and the brands of Lake copper reach a very high standard, both as regards electrical and mechanical properties. A still purer variety is the native metal from Yunnan, China.
The Lake Superior copper occurs in three formations:—
(a) Vein deposits, from which the enormous masses of copper are taken out.
(b) Copper-bearing ash beds, of amygdaloidal diabase. Chief mine, Quincy.
(c) Beds of conglomerate in which the cementing material consists partly of copper. This last class of deposits yields three-quarters of the Lake copper supply. Their average copper content is 2·9 per cent. The chief mines are the Calumet and Hecla, the Tamarack and the Atlantic, all situated on one ore chute measuring 3 miles in length, and worked to a depth of 4,000 feet.