Volltext Seite (XML)
GENERAL PART. ORES AND METALLIFEROUS DEPOSITS. § 1. Under the general term ores are comprehended all minerals and mineral aggregates, which from their metallic con tents attract the attention of the miner. Metalliferous de posits are therefore for us all local accumulations of minerals or mineral aggregates, which correspond to this demand. The idea of the terms ores and metalliferous deposits, in mining parlance, cannot be well expressed in a more precise or scientific manner. There is not any particular class of minerals, or of rocks, corresponding to these terms. To them belong native metals, metallic oxides, metallic sulphides, and even metallic salts and their combinations; but on the other hand not all metalliferous species of the Mineral Kingdom, because many of these cannot, either from their nature, or the too small percentage of a metal they contain, proportionally to its worth, be worked with profit. No rock, for example, contain ing 5 per cent of oxide of iron can be considered as an ore; while on the other hand a vein of quartz, with but 1 per cent of gold, would be regarded as a very rich and valuable metallic deposit; so relative is the idea. It is even possible, and has already occurred, that a mineral, which for a long time was useless to the miner, and on this account was not considered as an ore, has, by means of new discoveries, been included in the category of ores. Blende, for example, when it did not contain valuable metals, could hardly have been considered formerly as an ore, though commonly defi ned as such; but since a method has been discovered of extract ing Zinc from it with profit, it may be ranked without doubt among the ores. Far more striking are the cases of Clay and l