.Brown hematite, or brown iron ore, is a hydrated peroxide of iron, and has the same composition as red hematite, except that it contains about 14 per cent of water. It is generally found massive, more rarely crystalline, and a variety occurring in small rounded modules is called pea iron ore. When mixed with earth or clay, it forms the pigments yellow ocher and brown umber. Brown hematite is now an important ore in Great Britain, about 2,000,000 tons being annually raised. It occurs in different .geological formations, chiefly in Devonshire, the forest of Dean, South Wales, and in the co. of Antrim in Ireland; also in an earthy form in Northamptonshire. It is the ore chiefly smelted in France and Germany.
Bog iron ore is a variety of brown hematite, usually containing phosphorus, which occurs in marshy districts of recent formation.
Carbonate of iron, when found in a comparatively pure and crystallized state, is known as spathic, spatitose, or Tarry iron ore; but when impure and earthy, as clay ironstone and blackband ironstone. Spathic ore was little worked in England previous to 1851, soon after which it was discovered in Somersetshire. It forms mountain masses in various parts of Prussia and Austria, and is now much in demand to yield the spiegelcisen required in the Bessemer process. In its purest form it contains 48 per cent of iron; and in color it varies from white to buff or dark brown, some specimens of it taking a beau tiful polish, and looking like marble. The clay and blackband ironstones are essentially mixtures of carbonate of iron with clay, blackband having also a considerable proportion of cooly or bituminous matter. These dull earthy-looking ores occur abundantly iu Great Britain, and form, after coal, the greatest of her mineral treasures. Fully one third of all the ore mined in the country is obtained from the coal-measures, where for tunately both the fuel and the limestone, indispensable for the reduction of the iron, are also found. The ore occurs as balls or nodules in the shales, or in continuous beds. Some of these seams are full of fossil shells, and the ore is then called " musselband" ironstone.
• Formerly, the three great iron districts of Britain were South Staffordshire, South Wales, and Central Scotland, each producing nearly equal quantities, and together yielding about of the total produce of the country. Now, however, the bouth Staffordshire field is becoming exhausted, its produce being only about a fourth of what it was, while that of the South Wales and Scottish districts has increased, and is now yielding annually, the former a million and a quarter, and the latter more than three million tons of ore. North Staffordshire, Shropshire, Derbyshire, and the West Hiding
of Yorkshire, are the principal remaining districts yielding ores from the carboniferous beds. The iron from the West Riding ore is the best in Britain as regards quality.
There is yet another great iron district, yielding an ore belonging to a more recent formation than the carboniferous—munely, the Bus. This deposit, which scarcely more than 30 years ago was unknown, is now producing iron to the enormous amount of 1,375,000 tons per annum. It is the ironstone of the Cleveland hills, in the n.e. of York shire, which, from its resemblance to common sandstone, passed unnoticed till 1847. About that time, isolated blocks of it, found on the sea-coast, were discovered to con tain about 30 per cent of iron. On further examination of the district these were proved to be detached pieces of a massive bed, no less than 15 ft. thick, which could be traced for many miles along the sides of the hills. Some idea of the value of this vast deposit of iron ore will be found in the fact, that the ironstone seams of the coal-meas ures seldom exceed 20, and are worked as low as 8 incites in thickness. Another mass of ironstone of great thickness, also belonging to the lies beds, was more recently discov ered in North Lincolnshire. In oolite, too, beds of 'brown iron ore have been discovered in several counties, but chiefly in Nortlnunptonshire, where it has been worked with so much spirit, that about a million tons of ore per annum are now raised.
To those remarkable discoveries may be added that by Mr. Rogers of Abercarn, who first detected, some years ago, the value of the spathic ore in the Devonian rocks of Somersetshire, now largely worked. 'We may state, too, that hematite has recently been mined to some extent in the Shetland islands. About 420,000 tons of what is called " burnt ore" are now yearly obtained in Great Britain from the residue of iron pyrites (sulphide of iron) which has been burned to yield its sulphur for the manufacture of sulphuric acid. Fully 1,000,000 tons of iron ore. are now annually imported.