The American Cyclopædia (1879)/Bog Ore

BOG ORE, Meadow Ore, or Limonite (Gr. λειμών, meadow), a variety of iron ore, which collects in low places, being washed down in a soluble form in the waters which flow over rocks or sands containing oxide of iron, and precipitated in a solid form as the waters evaporate. It is deposited in the bottoms of ponds as well as swamps, and is found in beds now dry, above the level at which it must originally have been collected, or else these are the product of springs which have now disappeared. The roots of trees appear to have an influence in reducing the peroxide of iron in the sands they come in contact with to the protoxide, by the action of some organic acid. By this action the ore is rendered soluble, and is liable to be precipitated by change to an insoluble salt, induced by the influence of the air or other causes. As the waters run among deposits of vegetable matters, and this change slowly takes place, the oxide of iron replaces the woody fibre, retaining in its more solid material the exact form of the branches of trees, of the small twigs, and even of the leaves, with their delicate reticulations. Deposits of bright red peroxide of iron, made up entirely of masses of these forms, which are true ferruginous petrifactions, are worked as iron ore. Extensive beds exist at Salisbury and Kent, Conn.; also in the neighboring towns of Beekman, Fishkill, Dover, and Amenia, N. Y.; at Richmond and Lenox, Mass.; at Bennington, Monkton, Putney, and Ripton, Vt.; and at numerous other localities in the United States. The bog ore deposits of Monmouth co., N. J., contain them, among other varieties of the ore. In Piscataquis co., Me., a very remarkable and productive bed of these petrifactions has furnished the supplies of ore to the Katahdin iron works. In the ponds of Plymouth co., Mass., bog ores were found so abundantly, that in the early part of this century 10 small blast furnaces were kept in operation by them. As the supplies became exhausted, more ores of the same class were for a time brought from Egg Harbor, N. J. From the bottoms of the ponds the ore was raised into boats, as oysters are gathered, with long tongs. It was found in lumps of various sizes, some weighing even 500 lbs.; but usually it occurs in small, irregular-shaped pieces, or in the form of shot. When taken from swamps, the workmen were careful to cover the cavities with loose earth, leaves, bushes, &c., calculating upon another growth in 10 or 15 years; but their expectations were sometimes realized in seven years. Ehrenberg has detected in the ochreous matters that form bog iron ore immense numbers of organic bodies, which indeed make up the substance of the ochre. They consist of slender articulated plates or threads, partly silicious and partly ferruginous, of what he considered an animalcule, but which are now commonly regarded by naturalists as belonging to the vegetable kingdom, and are referred to diatomaceæ and desmidieæ. Bog ore contains phosphorus, arsenic, and other impurities, which greatly impair its qualities for producing strong iron. The pig metal obtained from it, called cold short, is so brittle that it breaks to pieces by falling upon the hard ground; but the foreign matters which weaken it also give to the melted cast iron great fluidity, which causes it to be in demand for the manufacture of fine castings, the metal flowing into the minutest cavities of the mould, and retaining the sharp outlines desired. The iron made from the bog ores of Snowhill, on the eastern shore of Maryland, notwithstanding its great brittleness, brings a high price at the great stove founderies of Albany and Troy, to be mixed with other qualities of metal for producing the best material for their excellent castings. Bog ores are very easily converted into iron, and when they can be procured to mix with other kinds of ore, they produce a very beneficial effect, both in the running of the furnace and in the quality of the iron. For these reasons, as also for the cheapness with which they are obtained, it is an object to have them at hand, though they seldom yield more than 30 to 35 per cent. of cast iron.