HEMATITE, native sesqnioxide of iron, Fe.O., a mineral widely distributed, and con stituting a valuable ore of iron. It crystallizes in the rhombohedral system, and also occurs in massive form, sometimes forming beds of great thickness. It has a hardness of from 5.5 to 6.5, and a specific gravity ranging from 4.9 to 5.3. It is usually dark gray or black in color, the earthy varieties being red. It has a metallic lustre, and is sometimes slightly magnetic, oc casionally even showing magnetic polarity. Hematite occurs in the rocks of every age. The extensive masses that occur in metamorphic rocks are believed to have been deposited, originally, in marshes, undergoing metamorpho sis at the same time as the rocks with which they are now associated. By many it is be lieved that the great beds in the Lake Superior region were laid down in .the sea as iron car bonate or silicate, and later weathered to hema tite, after the region became land. Fibrous and columnar forms of the mineral, brownish-red or black in color, are also known, and to these the name °red hematite' is sometimes applied. In crystalline and metamorphic rocks a variety known as °specular iron' is met with, which is distinguished by the presence of crystals having a splendid lustre. Hematite occurs in vast
quantities in various parts of the United States, notably in upper Michigan, in the Marquette district, and in the Menominee and Gogebic ranges, in northern Wisconsin; and in Saint Louis County, Minn., in the famous Mesapi Range. Iron Mountain, Missouri, is a hill about 200 feet high, the surface of which consists of loose blocks of hematite, many of which weigh as much as 10 or 20 tons. In 1914, hema tite yielded 91 per cent of the iron ore pro duced in the United States. The name "hema tite is from a Greek word signifying °blood,* and was given to the mineral by the ancients from its fancied resemblance to coagulated blood. Hematite is sometimes called "blood stone' at the present time, though that name is more properly applied to a green variety of quartz, which contains small spots of red jasper.
An allied mineral, consisting of hydrated ses quioxide of iron and known to mineralogists as limonite, is often popularly called Thrown hematite.' See IRON ORES.