Copper in the United States, exclusive of Alaska and Hawaii

The copper districts in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map. In compiling the map, the estimated total quantity of copper present before mining was used to assign districts to size categories, and both production and reserves are included without distinction as to the status of exploitation. Four categories have been distinguished: deposits that contain 50+ to 1,000 tons; 1,000 to 50,000 tons; 50,000 to 1 million tons; and over 1 million tons of copper respectively. In many of the smaller deposits copper occurs with other metals, as gold, silver; lead, or zinc, that may be quantitatively and economically more important than the contained copper. Thus, for example, a deposit that contains large values in gold or zinc may contain only a small amount of copper and is shown on this map as a small copper deposit.

Five principal morphologic types of deposits have been distinguished on the map by letter symbols. These are disseminated, replacement, vein, massive sulfide, and native copper deposits (see Explanation). They are not strictly genetic types, however, for the disseminated deposits, the massive sulfide deposits, and many of the vein deposits were formed largely or entirely by replacement processes.

The symbols show either individual mines or the approximate centers of districts. Some of the more prominent districts are identified by name on the map, and all with over 1,000 tons of copper are numbered to correspond to the Locality Index. As mining district names do not always correspond to locality names, and a name established through common usage may not be the legal name of the mining district, several names are given in the index for some localities. The index is arranged alphabetically by States. Both published and unpublished data were used, and at least one reference is given for each locality if reports on it have been published.