Minerals Present in Soil
Common minerals present in the soil are as follows:
- Hematite: It is a common iron oxide compound with the formula Fe2O3 and is widely found in rocks and soils. It is red to blackish-red in color. On absorbing water it swells up to form hydrated iron oxide. Clay-sized hematite crystals occur as a secondary mineral formed by weathering processes in soil, and along with other iron oxides it is responsible for the red color of many tropical, highly weathered soils.
- Limonite: Hydrated ferric oxide is called Limonite. It is yellow to brown in color. It is an important coloring and cementing agent in soil. Limonite is a residual soil produced by the decomposition of magnesium silicate (olivine) rocks in tropical environments. During weathering process most of the original rock is leached away leaving only its iron content, which is precipitated out in the form of iron sesqui-oxides to create a soft and highly porous soil.
- Goethite: Limonite when adsorbs water is called goethite. It is one of the most thermodynamically stable iron oxide. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment.
- Gibbsite: It is the most common aluminum compound found in soil. It is found in highly weathered soil. It is a major mineral in soils of the tropics and subtropics where it may be the dominant mineral in the clay fraction.
- Carbonate Group: Magnesium hydroxide and calcium hydroxide combine with carbon dioxide to form carbonates. Carbonates buffer soil pH and are an indication of the relative abundance of bases. The most common types are calcite (CaCO3) and dolomite [CaMg(CO3)2]. Less common soil carbonates include sodium carbonate (Na2CO3) and siderite (FeCO3).
- Calcite: It is generally white or colorless. It is a major constituent of sedimentary rocks and consists of calcium carbonate. Calcite is present primarily in arid and semi-arid regions, where the source was either limestone parent rock or calcareous air-borne dust, although in some climates the soil calcite is the result of coral and shells. Calcareous soils typically have a pH above 7.5.
- Dolomite: It is the chief source of magnesium in the soil. Dolomite, a type of limestone which provides valuable nutrients to plants and helps change the pH of the soil by raising it to match the plants’ needs. It is also known as dolomitic lime/limestone. It provides more nutrients than straight lime.
- Siderite: It is an important mineral found in water-logged soil. It is produced by the alteration of other iron-bearing minerals. Its chemical formula is FeCO3. This iron carbonate mineral is commonly found in sediments and soils. It has been used as iron ore and for steel production.
- Sulphate group: It is formed by the combination of Sulphur and Oxygen ions. It further reacts with calcium ions to form calcium sulphate.
- Gypsum: It is found in sedimentary rocks and desert soils. It is water-soluble and leaches easily. It is chemically calcium sulfate. It plays a beneficial role in breaking up compact soil, especially clay soil. It is useful in changing the soil structure of excessively heavy soils.
Mineral Riches in the Soil
Soil minerals are naturally occurring, inorganic substances found in soil, such as sand, clay, and various metal oxides. Minerals in the soil are essential for plant growth and soil fertility. The outermost layer of the earth, known as crust, is covered with a mixture of organic and inorganic material called soil.
Soil serves as a medium for the growth of plants as it is rich in minerals and useful living organisms. The mineral composition of the soil is about 45-50%, organic matter constitutes about 1-5% of it whereas the remaining space is filled with air and water. Soil minerals examples include quartz, feldspar, mica, iron oxides, and calcium carbonate. In this article, we will cover minerals in the soil, their types, uses, and more.
Table of Content
- What is Soil?
- Soil Minerals
- How Minerals Form in Soil?
- Soil Minerals Types
- Minerals Present in Soil
- Soil Minerals and Their Uses
- Conclusion – Soil Minerals
- FAQs on Soil Minerals
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