Spathic iron ore

Eisenstein, m. ironstone, iron ore. — spatiger —, spathic iron ore, siderite. 

Spat-eisen, n., -eisenstein, m. spathic iron ore, sparry iron, siderite. 

Side rite. FeCO-,. corresponding to 48.2 X P e. 51.86/ CO , sp gr 3.83 3.88. white to greenish-gray and brown, contains variable amounts of calcium, magnesium, and manganese, varies from dense, line-grained and compact to crystalline, sometimes referred to as spathic iron ore. or black-band ore. The carbonate ores are calcined... 

These consist essentially of ferrous carbonate, FeCOa, the purest form of which is spathic iron ore, which occurs both in the crystalline and the massive form. It is mined in Russia, Poland, the Balkans, Styria (Austria), Westphalia, and other parts of Germany. Its phosphorus content is low, but a considerable quantity of manganese is present. It is usually of a light brown colour and is possessed of a pearly lustre. 

Ferrous carbonate, FeC03, occurs in nature as spathic iron ore (see p. 20), which, however, is not pure, even m the crystalline form, as it contains several other isomorphous carbonates. When crystalline, the mineral is generally known as chalybite or siderite. The crystals belong to the hexagonal system, and are brown in colour. Upon exposure to moisture and air they are gradually converted into hydrated ferric oxide. When heated, they begin to decompose at about 400° C.4 in air. 

He recognised that the equality of angles is only approximate, and in the iso-morphous series of carbonates of calcium, magnesium, iron, and zinc he found a difference of as much as 2°, the same difference being foimd for barium and strontium sulphates. He mentions that Wollaston had already found small but measurable differences between the angles of calcite, dolomite and spathic iron ore. 

In a memoir on spathic iron ore (ferrous carbonate) read in June 1774, Bayen showed that the mineral on heating or dissolving in acids lost what the English call fixed air . He used Hales s apparatus, measuring the elastic fluid or gas (gaz) evolved, which he found was absorbed by fixed alkali (potassium carbonate) to form a crystalline salt (potassium bicarbonate). He concluded that the mineral is a compound of i part of fixed air or gas and 3 parts of metallic iron, but it is really a compound of i part of fixed air and i -6 of ferrous oxide. 

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