What makes igneous rocks good building materials

Igneous rocks are good for building material because they are hard, strong and give a good finishing eg. Their strength and hardness can also be a drawback since it makes them harder to cut.

Sedimentary rocks are easier to cut while still being strong enough and they are also widely available. Because they form within the Earth, cooling occurs slowly. Such slow cooling allows time for large crystals to form, therefore, intrusive or plutonic igneous rocks have relatively large mineral crystals that are easy to see.

Granite is the most common intrusive igneous rock Figure 4. Notice the black and white portions. Each color represents a different mineral in the rock.

You can easily see the mineral crystals that make up this plutonic igneous rock. Igneous rocks are called extrusive or volcanic when they form above the surface. They solidify after molten material pours out onto the surface through an opening such as a volcano Figure 4. Extrusive or volcanic igneous rocks cool much more rapidly and therefore have smaller crystals.

Since the rapid cooling time does not allow time for large crystals to form, minerals are not easy to see within the rock. Some volcanic igneous rocks cool so rapidly that crystals do not develop at all. These form a glass, such as obsidian.

This is a hard igneous rock made up of clearly visible crystals of various minerals. A dark-coloured, fine-grained rock. Basalt is one of the main rocks to form the oceanic crust the part of the Earth's surface under the Ocean. It is having fine to coarse grains. Alternative dark and white bands are common. Light grey, pink, purple, greenish-grey and dark grey coloured varieties are available.

These stones are not preferred because of deleterious constituents present in it. They may be used in minor constructions. However hard varieties may be used for buildings.

The specific gravity varies from 2. 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. This is a metamorphic rock. It can take a good polish. It is available in different pleasing colours like white and pink. Its specific gravity is 2. It is used for facing and ornamental works.

It is used for columns, flooring, steps etc. We have rock polishing tools that are all you need. It is a metamorphic rock which can be split easily and available in black colour. It is used for damp-proofing flooring and roofing. These are metamorphic rocks. They are composed of quartz, mica and clay minerals. The structure is fine-grained. They split along the planes of original bedding easily. The colour varies from dark grey, greenish-grey, purple-grey to black.

The specific gravity is 2. They are used as roofing tiles, slabs, pavements etc. 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. Quartzites are metamorphic rocks. The structure is fine to coarse-grained and often granular and branded. They are available in different colours like white, grey, yellowish.

Quartz is the chief constituent with feldspar and mica in small quantities. They are used as building blocks and slabs. 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. Generally, most of the building stones have a high strength to resist the load coming on it. Therefore it is not of prime concern when it comes to checking the quality of stones. But when the stones are to be used in large structures, it becomes necessary to check the compressive strength of stones.

Building stones should be capable of resisting the adverse effects of natural forces like wind, rain and heat.