Stone - Introduction

What is stone?

Stones( also seen as rocks), by definition are solid natural combination of minerals which forms the earth's crust. They are formed through different natural processes, depending on their type. Stones can be classified into sedimentary rock, metamorphic rock and igneous rock. Each of them varies in hardness, composition of minerals and formation process. 

1) sedimentary rock


How are they formed? 
Little fragments and sediments were eroded and redeposited by few thousand and even up to million years of wind and water. They settle below water, being compressed and cemented layer by layer, by the weight of water and themselves. Upon hardening, they form sedimentary rocks.


Nature: Soft and fairly porous






Examples of 
sedimentary rock: sandston, limestone, shale, conglomerate, gypsum.

2)metamorphic rock 

How are they formed?  

These rocks were once igneous or sedimentary rocks. Under extreme heat and pressure under earth, they changed in mineral forming metamorphic rock 

Nature: Hard and non-porous

Examples of metamorphic rock: schist, gneiss , marble , slate.

3) igneous rock

How are they formed?  

They are in molten state underground, called magma. After eruption of volcano, the magma comes to the surface as lava and upon cooling, it turns into igneous rock.

Nature:Hard and non-porous

Examples of igneous rock: granite, scoria, pumice, obsidian

The use of rock by humans dates back to prehistoric era such as the stone age and neolithic. Even though the stone age had ended long time ago, yet stone in architecture still remain till today.  

Stones are used in architecture because of their high durability, hence for protection purposes and stone buildings are built to last. They can be made into different sizes, shape,  colours and texture for different purposes such as roofing, flooring, walling, etc. Such stones that is being fabricated are called dimension stones. A classic example of a stone building is the pyramids in Giza.