Certain ore deposits (usually massive but irregular) which are situated mainly in Arizona constitute the third important general class. These deposits produce about one-quarter of the total United States output. Bisbee, Jerome and Globe (Arizona), and Kennecott (Alaska), are the main localities. Owing to the irregular nature of the deposits and the distance from the surface at which the ore is found, large developed reserves cannot be blocked out in advance. Such reserves are assumed to be five years. Apart from the three classes of deposits described above are many smaller deposits, of which the most distinct class are the pyritic bodies, notably those of Tennessee and California. Such deposits are often profitable even when of low grade, because the sulphur as well as the copper is recovered. Reserves in such deposits are large: equal, say, to ten years’ life. Deposits of this class are important in Spain, Norway and in part in Japan. Mines producing copper as a by-product should also be grouped here. From the above outline the table below has been compiled: TABLE 41.--DEVELOPED RESERVES OF UNITED STATES COPPER MINES ------------------------------------+----------+--------+----------- |Percentage| | | of | | | total |Years of|Extension General group | output | life | [118] ------------------------------------+----------+--------+----------- The “porphyries” | 35 | 26 | 9.10 Deep mines | 30 | 5 | 1.50 Rich ore bodies (Arizona and Alaska)| 25 | 5 | 1.25 Pyritic ore bodies | 5 | 10 | 0.50 Others | 5 | 2 | 0.10 +----------+--------+----------- Average | 100 | 12.4 | 12.45 ------------------------------------+----------+--------+----------- [118] “Extension” is the Percentage of Total Output multiplied by the Years of Life, giving the relative importance of each group. The known ore reserves serve as a basis for the assumption that the production of copper in the United States will continue at the present figures for at least ten years. CANADA Canadian copper-producing properties are entirely controlled by American and British capital in about equal proportion, changes involving construction of new refineries and a shift in selling control being assumed to be already effective. Up to the present time the natural development has been for Canada to depend largely on the United States for refining facilities. It is likely that in the future local or English control in this field will be closer than heretofore, although the Canadian copper industry will always be closely identified with that of the United States.