Minerals

     In the bowels of the earth are deposited a great variety of mine­rals that play a large part in the economic development of the world. They include fuel (coal, oil and natural gas), metallic ores, salts and building materials (clay, sand and limestone).
The distribution of minerals depends on the structure and compo­sition of the earth's surface.
Sedimentary Rocks. The outer crust of the earth is almost everywhere made up of sedimentary rocks. Sedimentary rocks are composed of alluvium and silt, deposited in layers on the beds of seas, lakes and rivers, or accumulated on land under the action of wind and water.

Fig. 26. A section of a coal-pit in the Ruhr:
1 — the coallift; 2 — the machine room; 3 — the cages in which the trol­leys and workmen go up and down; 4 — the horizontal underground pas­sages where the coal is extracted (the short vertical lines stand for timber supports against cave-ins); 5 — a trolley-train filled with coal; 6 — coal-beds shattered as a result of dis­placement around cracks; 7 — drainage pipes.

Such rocks include sand and clay, chalk and limestone. The last two consist of the remains of sea-creatures and of tiny shells.
Such minerals as salts on the beds of former seas and salt lakes, oil and coal, are also considered to be connected with sedimentary rocks.
Oil and Coal. On the beds of former seas the remains of sea-creatures and vegetations accumulated in great masses. Oil is the product of their decay.
In Europe oil is mainly found along the southern and eastern foothills of the Carpathians and in the region between the Volga and the Urals (the Ural-Volga region).
Many valuable products are processed from oil: benzine, kerosene, lubricating oil, synthetic rubber, etc.
Eastern Europe, in addition, is rich in natural gas, which is used as a fuel and in the pro­duction of fertilizers and other chemicals.

supplies of coal. The main coalfields are the Pechora Basin along the western slopes of the North Urals, the Donets Basin near the Donets Hills, the Upper Si1esian and Ruhr Basins at the foot of (he Central European ancient mountains and the Island of Great Britain, where there are also ancient mountains.
Coal is used as a fuel for plants and mills, power-stations and ships. From it, too, dyes, fertilizers, explosives and medi­cines are made. Of particular value are the kinds of coal from which coke is made. (Coke is the substance that remains after coal has been heated and cleared of ad­mixtures.) Coke is used in smelting ores, especially iron.
Igneous Rocks. Igneous rocks differ from sedimentary rocks. Igneous rocks originate from the cooling and hardening of molten matter from the earth's interior. Examples are granite and other hard rocks. Igneous rocks are usually deposited underneath sedimen­tary rocks. They are brought to the surface most frequently in ancient mountain districts where the upper layers have been removed. Ores are usually found in igneous rocks or close by.

worn away by time and carried to new places by wind and water, where they are deposited in combination with sedimentary rocks.
Iron Ore. Europe has ample supplies of iron. There are large de­posits of iron and other ores in the Ural Mountains. There are enormous deposits of iron ore in the East European, or Russian, Plain, especially in those places where igneous rocks are close to the surface. In this plain lies the Kursk Magnetic Anomaly with its huge deposits of magnetic iron ore. In this district the needle of the compass turns in the wrong direction («anomaly» means 'ab­normal'). South of the East European Plain is situated K r i v o i R o g, rich in iron ore and a great producer of that metal.
In Western Europe the chief deposits of iron ore are in the foothills of the. Scandinavian Mountains in the north and in the vicinity of the ancient mountains in the west (in France and other places).