Some coals will coke and others will not; nothing but a trial can settle this matter in each individual case. Good coking coal is very valuable.
Cobalt. Cobalt ores are always found in veins with other metals. Pure cobalt is extremely rare. Cobalt colors are used for porcelain painting, glass-staining, etc.
Chromium. All chrome is obtained from chromite, which contains 68 per cent. of chrome sesqui-oxide, the remainder being iron protoxide. Hardness, 5.5; gravity, 4.4; luster, sub-metallic; opaque. Steel-gray to almost black. Harsh. Brittle. Cleavage, imperfect. Fracture, uneven. Texture, massive to granular. Chromite in gravel looks like shot. Serpentine often contains it, when it is apt to resemble a fine-grained magnetite. It is used chiefly in iron and steel alloys, and in making armor plate. It is also used in dyeing fabrics and in paint manufacture. But little chrome ore is produced in the United States. The importation in 1899 was 15,793 tons, value $18.03 per ton.
| Chromite, FeOCr2O3 | 47-68 |
This ore is merchantable at $22 to $25 per ton.
Domestic ore ranges from $10 to $12 a ton, while the pure imported ores are worth $21 a ton. The yearly consumption in the United States is about 16,000 tons, and the American production 100 tons. This ore is useful as a lining for furnaces, and the demand promises to become important. Newfoundland is said to contain large deposits.
Copper. Native copper occurs in the Lake Superior region, but the demands of commerce are supplied from chalcopyrite or copper pyrites, and tetrahedrite or gray copper ore. Many different ores of copper may exist in the same vein. On the surface an iron cap of gossan reveals the deposit; immediately below may be black oxide of copper with some malachite, lower down red oxide, and below the water-line copper sulphides. The following are the principal copper ores:
| Sp. Gravity. | Hardness. | P. C. Cu. | |
| Native copper | 8.8 | 2.8 | 100 |
| Chalcopyrite | 4.2 | 3.7 | 35 |
| Enargite | 4.4 | 3.0 | 48 |
| Tetrahedite | 5.0 | 3.5 to 4.5 | 35 |
| Chalcocite | 5.6 | 2.7 | 80 |
| Bornite | 5.0 | 3.0 | 55 |
| Melaconite | 6.2 | 2.0 to 3.0 | 80 |
| Cuprite | 6.0 | 3.6 | 89 |
| Chrysocolla | 2.2 | 3.0 | 45 |
The common ore is native copper, often associated with native silver, the two remaining, chemically, quite distinct. Some masses of copper occur that are too large to handle and must be cut by cold chisels, a method that costs more for labor than the value of the metal. The Lake Superior mines produce 140,000,000 pounds of copper a year, while those of Montana made the gigantic output of 228,000,000 pounds in 1896. The great Anaconda mine, of Butte, is the heaviest producer, yielding more than half the state's total.
During 1899 the New York copper market rate varied between 14.75 cents and 18.46 cents per pound. Copper is probably abundant in the shape of pyrites in many parts of Canada, especially in the Northwest, and prospectors in that region should search diligently for it. The Lake Superior mines are unique in being deposits of native copper.