Iron Ores

Character of Pig-iron. —Ores suitable for “gun-metal” should be reduced in the smelting-furnace, with charcoal and the warm blast, varying from 125° to 300° Fahr., depending upon the ore used. Iron thus made, or pig-iron, should be soft, yielding easily to the file and chisel; the appearance of the fracture should be uniform, with a brilliant aspect, dark gray color, and medium-sized crystals. Character of Gun-metal. —When remelted and cast into cannon, it should approach that degree of hardne which resists the file and chisel, but not so hard as to be bored and turned with much difficulty. Its color should be a bright, lively gray; crystals small, with acute angles, and sharp to the touch; structure uniform, close, and compact. Magnetite. — Octahedral Iron Ore. —Color iron-black. Streak black. Brittle. The black streak and magnetic properties distinguish this species from the following: Specular Iron Ore. — Hematite. —Often ma ive granular; sometimes lamellar or micaceous. Also pulverulent and earthy. Color, dark steel-gray or iron-black, and often when crystallized having a highly splendid lustre; streak-powder cherry-red or reddish-brown. The metallic varieties pa into an earthy ore of a red color, having none of the external characters of the crystals, but perfectly corresponding to them when they are pulverized, the powder they yield being of a deep red color, and earthy or without lustre. Sometimes slightly attracted by the magnet. Limonite. — Brown Iron Ore. —Usually ma ive, and often with a smooth botryoidal or stalactitic surface, having a compact fibrous structure within. Also earthy. Color, dark brown to ochre-yellow; streak, yellowish-brown to dull yellow. Lustre, sometimes sub-metallic; often dull and earthy; on a surface of fracture frequently silky. Spathic Iron. — Carbonate of Iron. — Chalybite. —Usually ma ive, with a foliated structure, somewhat curving. Sometimes in globular concretions or implanted globules. Color, light grayish to brown; often dark brownish-red, or nearly black on exposure. Streak, uncolored. Lustre, pearly to vitreous; translucent to nearly opaque.