Components, rocks, soil

Gays are an essential component of soils, to which we owe our survival, and they are also the raw materials for some of mankind s most ancient and essential artefacts pottery, bricks, tiles, etc. Clays are formed by the weathering and decomposition of igneous rocks and occur typically as very fine panicles e.g. kaolinite is formed as hexagonal plates of edge. 1-3 p m by the weathering of alkaline feldspar... 

The inorganic component of soil is dominated by four elements O, Si, Al, and Fe (Jackson, 1964). Together with Mg, Ca, Na, and K they constitute 99% of the soil mineral matter (see Table 8-2). Minerals in soil are divided into primary and secondary minerals. Primary minerals, which occur in igneous, metamorphic, and sedimentary rocks, are inherited by soil... 

The feldspars are aluminosilicates in which up to half the Si44 ions have been replaced by Al3+ ions. They are the most abundant silicate materials on Earth and are a major component of granite, a compressed mixture of mica, quartz, and feldspar (Fig. 14.45). When some of the cations between the crystal layers are washed away as these rocks weather, the structure crumbles to clay, one of the main inorganic components of soil. A typical feldspar has the formula KAlSi3Og. Its weathering by carbon dioxide and water can be described by the equation... 

Arsenic is a metalloid, but it is generally included in work on metals in food. It is rarely found as the free element in the natural environment, but more commonly as a component of sulphur-containing ores in which it occurs as metal arsenides. Arsenic is present in rocks, soils, water and living organisms in concentrations in the parts per million (mg/kg) range. 

In general, soil is an unconsolidated combination of inorganic and organic materials. The inorganic components of soil are principally the products of rocks and minerals that have been gradually broken down by weather, chemical action, and other natural processes. Soil particles, also known as soil separates, are divided into three main size groups sand, silt, and clay minerals [14]. 

The components of soils and rocks have different size, shape, and quality. The particle size of organic components usually is in the colloid range (<500 nm) mineral components have different dispersity. The first classification system of soils on the basis of particle size was done by Atterberg (1905). Practically, this classification has been used until now, though some countries have their own classifications, considering their widespread soil types. The size of soil particles will also determine how the soil fraction is named (e.g., clay, sand, silt, rock, etc.). Table 1.6 provides these names along with the standard diameter of the particles for the international classification system. 

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