As in the earlier post, it is mentioned, that the usage of rocks as building stone is totally dependent on their strength and durability. Some of the properties which make the rocks eligible for usage as a building material are their strength, permeability, durability, and resistance to heat. Keeping in view these properties geologist chose some of the rocks, which can be used for construction successfully. Among these rock, the most common are as follow;
Granites are used for construction purposes on account of their high crushing strength, low porosity, and pleasing pink or grey colours. They are capable of taking good polish. Granites are commonly used for massive masonries, and for architectural and ornamental work. The granites occur abundantly in regions occupied by the Archaean rocks.
(2). Basalt and Dolerite:
The Basalts and Dolerites are fine-grained igneous rocks of basic composition. These rocks serve as excellent road material because of their high crushing strength and durability. Although the basalts are easily workable and a durable stone, they are not used commonly as building stone due to their dull and unpleasant colour.
(3). Sandstones and Quartzites:
Well cemented sandstones generally have all the characters of good building stones. In Pakistan, the sandstones of the Balochistan Plateau are transported all through the country to meet the need of construction material. In villages, small buildings are made with sandstone and mud mortar. The sandstones are used both for masonry and for flagstones. On the other hand, Quartzite does not form good building stone because they are extremely hard in nature, and their this nature renders difficulty to the work.
(4). Limestone and Marble:
Limestone is a sedimentary rock made up of Calcium Carbonate, while marble is a metamorphic form of limestone. Because of their homogeneous texture, easy workability and pleasing colours, limestone and marble form good building and ornamental stones. The limestone are not only used as building stones, they are also used in making lime and cement.
Shale is a commonly found sedimentary rock, which can be used as a raw material for making many types of brick, tile, pipe, pottery, and other manufactured products. Brick and tile are some of the most extensively used and highly desired materials for building homes, walls, streets, and commercial structures. When shales are subjected to heat and pressure of metamorphism alter into a hard, fissile, metamorphic rock known as slate. With continued increase in metamorphic grade the sequence is phyllite, then schist and finally gneiss.
The slate is a metamorphic rock, which can be broken easily into thin smooth slabs. It is used chiefly for roofing and paving in buildings.