The chromic iron ores produced in the former Austrian Empire have come mainly from the central part of Bosnia, but the chromite mines in Upper Styria and those on the Roumanian border have also furnished an appreciable output, the ore being low-grade. The deposits of Bosnia are in serpentine. The ore is of good quality and has been mined for use as a furnace lining. On and near the left bank of the Danube River in the Banat, Hungary, there is an extensive area of serpentine containing chromite in bunches. The deposits have been worked to a slight extent.
North America.
—In Canada chromite-bearing areas of considerable extent are found in the southern part of the Province of Quebec, where nearly all the productive chromite mines of Canada are situated. The ore occurs in serpentine in irregular masses and pockets without definite form, that range in size up to 75 feet along the longer axis, rarely reaching 100 feet. The amount of high-grade ore in the Quebec chromite deposits is not large, but low-grade ore bodies which under normal market conditions can not be mined at a profit are numerous and of large size. The low-grade ores range in content of chromic oxide from less than 20 per cent. to 35 or 40 per cent. Nearly all the Canadian ore mined has been exported to the United States. From 1910 to 1914 the output of chrome ore from the Quebec mines was insignificant, owing to the cost of mining low-grade ores and the lack of a market for them. When the price of chromite rose late in 1914, American firms began active developments in the field, and subsequently two concentrators were built by the Mutual Chemical Co. The output of Canadian chromite, both of crude ore and concentrates, during the war period was noteworthy, the production rising from 121 long tons in 1914, to 47,035 long tons in 1916 and 43,725 long tons in 1917.
The principal American firms interested in the development of the Canadian chromite deposits during the past few years have been the Mutual Chemical Co., the Harbison-Walker Refractories Co., the Electrometallurgical Co., and the Quebec Asbestos & Chrome Co. The last-named company purchased one of the concentrators built by the Mutual Chemical Co., and has furnished a considerable output both of crude ore and concentrates. Canadian firms have also produced considerable ore.
With the close of the war and the drop in the price of chromite, the Canadian mines have been largely abandoned. It is possible, however, that some American firms that mine ore for use in their own plants may continue work on a small scale.
When the United States was the world’s principal chromite-producing country, the output came from the eastern United States and principally from Maryland. The Wood chrome mine and neighboring deposits in Baltimore and Harford counties furnished most of the production. Smaller amounts were mined in North Carolina and Pennsylvania.
The principal chromite deposits of the United States, and those that have furnished nearly all the ore produced in recent years, are in California and Oregon. Recently deposits of some extent have been found in Montana, but these have not reached the producing stage. The chromite deposits of California are for the most part grouped into four principal districts, the Klamath Mountains region of northwestern California and southwestern Oregon; the Coast Range of west central California; the Sierra Nevada range throughout a considerable part of its length; and the San Luis Obispo district of southwestern California.
The chrome ores of California and Oregon form lenses or irregular bodies in serpentine and related rocks. Many of the ore bodies are found in comparatively fresh peridotite and dunite, and the intimate relation between the chromite and the associated pyroxene or olivine is well shown. In places, also, chromite masses are found in the mantle of residual material derived from the alteration of serpentine and other rocks. Most of the chrome ores of the Pacific Coast are of low-grade, few running more than 45 per cent. chromic oxide. Concentrating plants have been built to beneficiate the ore from bodies large enough to warrant such expenditure. At some plants the grade of ore was thus raised to more than 52 per cent. Locally small bodies of high-grade ore have been found.
The chromite mines of the eastern United States were first worked about 1827 and continued to be operated for about forty years. The California deposits began to be developed about 1870, but never furnished a large output until the war raised the price of chromite to unprecedented figures and ore could be produced at a profit in spite of high costs and high freight rates to consuming centers. The chromite mines of the United States have always been worked and controlled by American capital. In California the ore has been mined mainly by private individuals working small scattered deposits. A few large firms, such as the California Chrome Co., the Adams & Maltby Co., L. H. Butcher Co., and the Union Chrome Co., worked on a larger scale during the war period.
Deposits of chromite have been known in Alaska for a number of years, but not until the war brought high prices was it possible to mine them at a profit. The deposits of present importance are near the southwestern end of the Kenai Peninsula. About 1,000 tons of ore containing 46 to 49 per cent. chromic oxide was mined in 1917.