CHROMITE, or CHROMIC IRON, the only important ore of the metal chromium and the source of all of the chromium salts. Chemically considered it is a chromate of ferrous iron FeCr204, but it is usually classified by mineralogists among the oxides of the spinel group as a compound of iron protoxide, with chromium sesquioxide, having the formula FeO.Cr,O,. The metals are often in part re placed by magnesium, aluminum and ferric iron, as in the varieties magnochromite from Silesia and mitchellite from Webster, N. C. The composition of the mineral thus approaches the chromiferous variety of spinel, piootite. Chromite has a hardness of 5.5 and a specific gravity of 4.32 to 4.57. It is usually a granular massive, black, opaque, metallic mineral, much resembling magnetite. It has, however, a dark brown streak and is readily distinguished from all black minerals by fusing it with borax and salt of phosphorus, the bead thus obtained as suming an emerald-green color on cooling. It is further identified by its invariable occurrence in serpentine or olivine rocks. It is often disseminated in grains, or rarely in small octa hedral crystals, and thus upon the disintegrati^n of the rock the grains are washed into the streams and adjoining bottom-lands. Prior to 1884 it was extensively mined near Baltimore, also at Texas, Pa., and in California, North Carolina and Wyoming.
The production of chromite in the United States experienced a notable expansion in 1916, in the output of 47,035 long tons —more than 15 times the previous record output of 3,280 tons, mined in 1915. This was due primarily to the unprecedented demand for chrome steel for war purposes, but also in large measure to the scarcity of ocean tonnage from Africa and Oceania, which countries had heretofore been depended on as the chief sources of sup ply. However, in spite of this difficulty in trans
portation, the importation was 115,945 tons, a gain of 39,490 tons, or nearly 52 per cent.
The United States' production came prin cipally from California, which yielded 92 per cent of the country's total, the remaining 8 per .cent being nearly all from Oregon, with small additions from Maryland and Wyoming. Chro mite is found in deposits of serpentine, where the latter has been disintegrated by weather and erosion. The black grains and boulders of the chromite accumulate in the surface soil, and in concentrated masses, in connection with magnetite, in the black sands of the streams and beaches. In quality the California chro mite ranges up to 48 per cent of chromic oxide, and the Oregon mineral up to 56 per cent.
The importations of chromic iron ore into the United States in 1916 were as follows: From Rhodesia, 61,850 tons; from New Cale donia (French Oceania), 33,936 tons; from Canada, 12,220 tons; and from Greece, 7,000 tons. Asia Minor formerly supplied the United States with about 10,000 tons of diro mite annually, but since Turkey entered the European war that source has been cut off.
Under the stimulus of the war demand Canada's output of chromite has been very largely increased, and her exports of the ore to the United States in 1916 exceeded those of 1914 by more than 2,300 per cent. Consult California State Mining Bureau