Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER in. METHODS OF COPPER ASSAYING. The first step usually taken in the treatment of an ore of copper is to learn its value by determining the proportion of that metal that it contains. This process is called assaying, as distinguished from chemical analysis, which includes the further investigation as to the general composition of the ore. We shall confine our discussion in this place to assaying only. The assaying of any given parcel of ore is necessarily preceded by the process of sampling, by which we seek to obtain, within the compass of a few ounces, a correct representative of the entire quantity of ore, which may vary in amount from a few pounds to several thousand tons. As a rule, it will lessen the chance of serious error in very large transactions, to divide the lot into parcels of not over fifty tons each, and sample each of these lots by itself. The utmost care and vigilance in sampling and assaying should be required at every smelting-works, both in the interest of the works and in that of the ore-seller. Until quite recently, it has been customary to sample lots of ore by quartering them down, rejecting a certain proportional part at each successive operation, and reducing the size of the ore fragments as the quantity to operate on diminishes. This is a laborious and expensive method, and in the case of finely pulverized ores, may well be replaced by the use of the " split shovel," or one of the many automatic sampling machines that have been invented. But since the establishment of public sampling works at most of our great mining centers, where the correctness of the sample is guaranteed by the works, which distribute packages of each lot of ore to the agents of the various rival smelting companies, for them to assay and bid upon, the vast qu...