The writer has consulted a number of authorities on mining lines to ascertain just what sort of a position to give to the practice of ore dressing. Prof. Robert H. Richards, the head of the mining department in the Massachusetts Institute of Technology, and the inventor of machines which have made him famous among mining men, says, "Ore dressing is an essential part of mining. The whole object of ore dressing is to remove gangue before shipment and so save in freight and treatment charges." Mr. A. G. Charleton, the eminent English mining engineer and author of numerous books, in discussing this question, writes, "Personally, I am of the opinion that ore dressing should be included in mining." One has but to look through the catalogues of most of the American and foreign mining schools to find that little or no line is drawn between the courses in mining and metallurgy, and almost universally the dressing of a mine's product is taken up as an inseparable part of mining. In a very few exceptions, the courses of study are so planned as to draw an imaginary line between mining and metallurgy, and in these instances, ore dressing is placed with metallurgy only for convenience in the use and arrangement of college laboratories. But, since it is a common practice for mining companies to install plants right at the mines for the purpose of diminishing the bulk of ore shipped and to thus save in freight and custom treatment charges, mine superintendents and even the common miners have become accustomed to thinking of such plants as but units of the "mining" plants. At bituminous and anthracite mines whose products contain objectionable amounts of impurities, it is a common practice to subject the output to a Washing to remove the deleterious substances before shipment to the market.
Coal Washing Plant, Pana, Illinois.
In view, then, of these reasons, it is proper to decide that mining is a term broad enough to cover the operations of extracting coal and metallic ores from the ground and of preparing them for shipment or metallurgical treatment.
Coal is always coal, no matter in what thickness of deposit it is found. It may not be minable coal because in thin seams or because so intercalated with layers of slate or "bone," that the mine's mixture, or so-called "run of mine," is not salable. But with metallic ores, we run across an idea that is occupying the attention of many prominent geologists and mining men.
What is ore? This is a question to which there have been many attempted answers. There has been an evolution of ideas, with a corresponding gradation of definition. To set a uniform standard of thought upon this point, officers of the United States Geological Survey, a few years ago, proposed the following definition. It must be conceded that this definition, while embodying many splendid features, is not altogether exempt from criticism; but in the absence of anything better, we shall not be very far in error if we use it:
Ore is a natural aggregation of one or more minerals from which useful metal may be profitably extracted.
There is, then, no such thing as "pay ore" or "non-pay ore," expressions still quite common among miners and prospectors of the uneducated types. Prof. James F. Kemp, probably America's best-posted writer upon the subject, in an attempt to formulate one acceptable and unchangeable meaning for the word ore, says, "In its technical sense, an ore is a metalliferous mineral or an aggregate of such minerals, more or less mixed with gangue, and capable of being won and treated at a profit. The test of yielding the metal or metals at a profit seems to me, in the last analysis, the only feasible one to employ." This definition eliminates one of the weak points in the first definition, namely, that an ore must be an association of minerals: there are some common ores (as for example, magnetite) which are not associations, but single minerals.
We now reach certain fundamental concepts which must be accepted by the mining man who desires to be recognized as abreast of modern ideas. Following the publication of Kemp's definition of ore, there was much comment—as was anticipated—with the result that there has been noted a vacancy in scientific matters and it has been thought proper to permit another definition for purely scientific uses. This other definition of ore will cover the materials or aggregates of minerals from which gem stones and other valuable, but not metallic, substances are recovered.
Let us recapitulate. An ore must be an aggregate or association of natural minerals, or a single mineral, from which metal may be profitably recovered. Mines are excavations in the earth from which ore, coal or gems are taken. Mining is the art or practice of operating mines.