Iron Bearing Rocks

Iron ores are mostly oxides of iron with accompanying elements such as sulfur, phosphorus, manganese, silicon and earthy such as chain, clays and silica.

The elements which make up the earth have formed compounds with each other under the widest possible range of conditions, e.g. heat pressure, wind and water, oxygen, sulfur, phosphorus, silicon and carbon, for example have combined with metals to form ores. The brownish red-color of the soil is often a sign of the presence of iron compounds.

Ores are minerals (rocks). Metals are present in these ores in chemically combined form, mixed with lumpy waste rock (mullock). The ores are smelled if they contain useful metals in proportions with make it economically viable to extract them. In the case of iron, the minimum content considered economically viable is 25% and for copper around 0,6%.

Ores are classified according to the extractable metal in them, e.g. iron, copper, tin, lead, zinc and nickel ores.

Experiment 1: oxide ores contain iron combined with oxygen. If sheet steel or steel wool is heated, a black scale forms on the surface. This compound looks like magnetite.

Conclusion 1: iron and oxygen combined chemically to form iron oxide. Compound with oxygen are known as oxides.

Experiment 2: testing steel and iron ore for magnetic properties. Steel is attracted by a magnet, whereas brown hematite is not.

Conclusion 2: iron is not present in elementary form in ores. Ores contain chemical compounds of iron.

Experiment 3: the iron contained in hematite is chemically combined with oxygen and water. To begin with, bright steel wool is placed in two test tube forms in test tube after a few hours. The rust is similar of iron with atmosphere oxygen and water.

Experiment 4: the iron is sulfide ores is chemically combined with sulfur.

Iron powder and sulfur are mixed in the ratio 7.4 by weight. No reaction takes place, the iron be separated from the mixture with a magnet. If the mixture is heated, however, it suddenly glows brightly. After it has cooled, the mass has a different appearance and is no longer magnetic. It is similar to sulfurous iron ore.

Conclusion 4: iron and sulfur combine to from iron sulfide.

The principle elements with which iron has combined in the formation of ores are oxygen, sulfur and carbon. Iron ores which are smelled contain 25% to 70% iron. Important ores are magnetite (Fe3O4) with 50% to 75% iron, brown hematite (2 Fe2O3.3 H2O) with 50% to 75% iron, hematite (red iron ore, Fe2O3) with 30% to 50% iron and chlybitte (FeCO3) with 30% to 45% iron.

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