Mineral Matter

Mineral matter is the predominant component of mineral soils. It constitutes about 45% of total soil composition. It is made up of a number of particles which vary in size, shape and chemical composition. These particles range from the microscopic colloidal clays to the coarse fraction of sand and gravel. In nature, mineral matter exists as a dispersed phase, implying that it can be separated into the individual particles that comprise it. Along with soil organic matter, it makes up the solid materials phase of the soil.

Generally, mineral matter is divided into sand, silt and clay, which are often considered as the main mineral particles. These are collectively called soil separates and they are often cemented or aggregated together to form peds and aggregates. All the constituents of mineral matter are products of weathering and as such, they share a common origin – the massive soil forming rocks. They are therefore mineral in nature.

The constituents of mineral matter are mostly divided into primary minerals and secondary minerals:

The primary minerals are the broken-down remains of massive rocks which retain much of the composition of the rocks from which they originated. Primary minerals are products of accelerated physical weathering and they are often bigger and of a coarser texture. Primary minerals make up gravel, sand and some of silt.

On the other hand, secondary minerals result from the weathering of less resistant minerals. Unlike the primary minerals, secondary minerals do not bear any resemblance to the original material, as they do not retain the structure, properties or composition of the original mineral. Secondary minerals are the products of chemical weathering and are often smaller and of a finer texture. Secondary minerals make up the clays and some of silt.

Some important functions of mineral matter in soils are:

        –     It forms a greater part of the body of mineral soils therefore; they contribute more to soil mass.

      –  It determines, through its composition, the soil texture and therefore, the soil texture class of a soil.

       –     It holds and supplies nutrients to the plants it supports.

    –   It also gives support to erected structures and other constructions on the earth’s surface.

     –    It strongly influences – through its composition – the use to which a particular soil is suited.

Further Studies in this theme:

Composition of the Soil

Organic Matter

Soil Air

Soil Water