Stones

A building stone is a piece of rock quarried and worked into a required size and shape for a particular purpose. A building stone may be defined as a sound rock that can be safely used in some situation in the construction as a massive dressed or undressed unit. Granites and marbles used in the form of finely dressed blocks or slabs or columns in monumental and costly buildings, are good building stones. Similarly, sandstones and limestone used in forts, retaining walls and boundary walls and also as blocks in stone houses and bungalows are typical building stones. Slates used in many areas as roofing material for ordinary constructions and in pavements also fall in the category of building stones. The stones are used in the construction of buildings from the ancient times and most of the ancient temples, forts and mosques were built with stones as the major material. At present, they are largely used as the basic material for the manufacturing of the other construction materials like concrete, bricks etc.

Stone masonry is an engineering art that is preserved in many historical buildings in all parts of the world. This skill is still used, though on a lesser scale (because of the advent of concrete) in the construction of common residential houses and palatial buildings in many places. The Taj Mahal at Agra, the Red Fort in Delhi and temples of Lord Jagannath puri are some of the best known stone marvels of India. Following are the various uses to which stones are employed.

1) Structural elements: The stones are used for foundations, walls, columns, lintels, roofs, floor, damp proof courses etc.

2) Facing: The stones are adopted to give massive appearance to the structure. The walls are of bricks and facing is done in stones of desired shades. This is known as the composite masonry.

3) Paving: The stones are used to cover floor of buildings of various types such as residential, commercial, industrial etc. They are also adopted to form paving of roads, footpaths etc.

4) Basic Material: The stones are disintegrated and converted to form a basic material for cement concrete, moorum/murrum of roads, calcareous cements, artificial stones, hollow blocks etc.

5) Miscellaneous uses: In addition to the above uses the stones are also used as:

i) Ballast for railways
ii) Blocks in construction of bridges, piers, abutments, retaining walls, light houses, dams etc.

iii) Flux in blast furnaces

Type of Stones

1) Granite

It is a deep seated igneous rock, which is hard, durable and available in various colours. It has a high value of crushing strength and is capable of bearing high weathering. Granite is used for bridge components, retaining walls, stone columns, road metal and ballast for railways, foundation, stone work and for coarse aggregates in concrete. These stones can also be cut into slabs and polished to be used as floor slabs and stone facing slabs. Granite is found in the states of India like Maharashtra, Rajasthan, Uttar Pradesh, Madhya Pradesh, Punjab, Assam, Tamil Nadu, Karnataka and Kerala.

The minerals of granite are quartz, feldspar and mica. It has a specific gravity 2.63 to 2.75. They also have light or dark grey, pink or reddish colour. They have a crushing strength of 1000 to 1400 kg/m². It is very strong heavy, hard durable. It contains silica of about 60 to 80%.

2) Sandstone

This stone is form of sedimentary rock formed by the action of mechanical sediments. It has a sandy structure which is low in strength and easy to dress. They are used for ornamental works, paving and as road metal. It is available in the states of India like Madhya Pradesh, Rajasthan, Uttar Pradesh, Himachal Pradesh and Tamil Nadu. Sandstone is composed of sand grains, cemented together by calcium or magnesium carbonate or silicic acid, alumina and also oxide of iron. It also has a specific gravity 2.25. They have white, grey, brown or red in colour. It has a crushing strength of 400 to 800 kg/m². These are strong under pressure, but it is flaky when it contains mica. They are easily workable and also resists the weathering in a better way.

3) Limestone

It is a sedimentary rock formed by remnants of seaweeds and living organisms consolidated and cemented together. It contains a high percentage of calcium carbonate. Limestone is used for flooring, roofing, pavements and as a base material for cement. It is found in the states of India like Maharashtra, Andhra Pradesh, Punjab, Himachal Pradesh and Tamil Nadu. These are carbonate of lime intermixed with other minerals and impurities such as silica, magnesium carbonate, aluminium and iron. It has yellow, brown, grey or violet colour. It has a specific gravity 2.56. They have crushing strength 300 to 500 kg/m². These are soft and absorbent and so they do not resist the weathering action properly.

4) Slate

These are also composed of silica and alumina. These are usually grey-black or dark blue in colour. It has a specific gravity of 2.8. It has crushing strength 700 to 2100 kg/m². It is a metamorphic rock which can be split easily. It is used for damp-proofing, flooring and roofing.

5) Basalt and Trap

They are originated from igneous rocks in the absence of pressure by the rapid cooling of the magma. They have the same uses as granite. Deccan trap is a popular stone of this group in South India.

6) Gneiss

It can be recognized by its elongated platy minerals usually mixed with mica and used in the same way as granite. They can be used for flooring, pavement and not for major purposes because of its weakness. It is found in the states of India like Karnataka, Andhra Pradesh, Tamil Nadu and Gujarat.

7) Marble

It is a metamorphic rock which can be easily cut and carved into different shapes. It is used for ornamental purposes, stone facing slabs, flooring, facing works etc. It is found in the states of India like Rajasthan, Gujarat and Andhra Pradesh.

8) Quartzite

It is a metamorphic rock which is hard, brittle, crystalline and durable. It is difficult to work with and used in the same way as granite but not recommended for ornamental works as it is brittle.

9) Laterite

It is decomposed from igneous rocks; occur in soft and hard varieties. It contains a high percentage of iron oxide and can be easily cut into blocks. The soft variety is used for walls after curing while the hard blocks are used for paving the pathways.