COMMON BUILDING STONES AND THEIR USES

Various type of stone can be used in buildings depending on the type for masonry, flooring, roofing and paving roads as well as aggregates for concrete. We should have enough knowledge of Geology to identify rocks from their appearance and   texture. Some of the common stones found in India and their uses are as follows :-

1. Gravel :-

It is mixture of rounded water worn pebbles of any kind of stone with sand. It is usually available in river beds. The size of the pebble varies from minute grains to 8 cm in diameter. It is suitable for surfacing road and is also used in concrete.

2. Basalt :-

Basalt is an igneous rock that is formed from molten rock that has solidified under pressure. It has a uniform grey colour and is very hard and compact. Its most common use is as an aggregate but polished basalt is also used for flooring, monuments and other stone objects.

3. Granite :-

Granite is an igneous rock composed of quartz, mica and feldspar. It is common and widely occurring and is nearly always massive, hard and tough which makes it suitable for applications that will require wear resistance. It can range in colour from light grey to black, pink, blue and green, according to the mineral content.

Its colours, toughness and low porosity make it a popular choice for kitchen worktops, as it is attractive and resists heat and spillages of food and drink. Internally it is also used for tiles, fireplaces, staircases, where the weight is not a problem, bar tops and table tops. It also lends itself well to use outdoors for water features, monuments and paving.

4. Limestone :-

Limestone consists of calcium carbonate formed at the bottom of shallow lakes and seas that has been compacted over time. The primary source of calcite in limestones is marine organisms although other sources do occur. The presence of these organisms means that the stone often has fossil inclusions that form an attractive feature when the stone is polished or honed. It can be categorised as either soft or hard limestone. Various colours can be found as a result of the presence of different minerals in the limestone.

Limestone lends itself to use as floor tiles throughout a building and bathroom wall tiles, shower trays, cladding and vanity tops. In addition, fireplaces and staircases are often manufactured in limestone to striking effect.

5. Marble :-

Marble is a metamorphic rock that is predominantly composed of calcite or dolomite crystals. It is characterised by its crystal-like texture which is formed by limestone being changed by a combination of heat and pressure. It is both hard and compact.

It has been used as a building material for centuries and is suitable for many applications. It is most often used in bathrooms, spas and so on as wall and floor tiles as well as cladding, baths, work surfaces, basins and shower trays

6. Sandstone :-

Sandstone is composed of quartz particles that have eroded from other rocks, commonly granite, and cohered together with natural cement minerals in ground water before being compacted. The stone’s colour depends on the colour of the sand but tends to warm reds, yellows and oranges. It is often used for building and paving materials and other outdoor uses.

7. Chalk :-

It is pure, white limestone. It is soft and can be easily powdered. It is largely used for the manufacture of Portland cement. It is also used for marking and as a colouring matter. It is unsuitable for building purposes.

8. Shingles :-

These are large water-worn pebbles found in river beds. Broken shingles are used in concrete and as road metal when no better stuff is available at reasonable cost.

9. Quartzite :-

It is composed of silica and is dense, hard and glassy in structure. Some of the varieties are considered as the hardest and strongest type of building stones. It is strong and durable and used as road metal or railway ballast or in concrete.

10. Laterite :-

 It can occur in hard and soft varieties. The  soft variety is used for walls after curing while the hard variety is used for paving the pathways. They can also be formed as sedimentary rocks when it is called secondary laterites.

Gneiss :-

Gneiss is a common and widely distributed type of metamorphic rock. Gneiss is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Orthogneiss is gneiss derived from igneous rock (such as granite). Paragneiss is gneiss derived from sedimentary rock (such as sandstone). Gneiss forms at higher temperatures and pressures than schist. Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct foliation.