STONE/ROCK - as a building material - Classification of rocks

 

STONE/ROCK 

Definition :

A stone is a piece of rock. It is a mass of hard, compacted mineral. The word is often used to mean a small piece of rock.The word "stone" also refers to natural rock as a material, especially a building material.

Classification of Rocks: 

Building stones are obtained from rocks occurring in nature and classified in three ways. 

1. Geological classification 

2. Physical classification 

3. Chemical classification 

I. Geological Classification:

According to this classification, the rocks are of the following types. 

a. Igneous rocks: Rocks that are formed by cooling of Magana (molten or pasty rocky material) are known as igneous rocks. Eg: Granite, Basalt and Dolerite etc. 

b. Sedimentary rocks: these rocks are formed by the deposition of production of weathering on the pre-existing rocks. Examples: gravel, sandstone, limestone, gypsum, lignite etc. 

c. Metamorphic rocks: These rocks are formed by the change in character of the pre-existing rocks. Igneous as well as sedimentary rocks are changed in character when they are subject to great heat and pressure. Known as metamorphism. Examples: Quartzite, Schist, Slate, Marble and Gneisses.

II. Physical Classification: 

This classification based on general structure of rocks. According to this, the rocks are classified into three types 

a. Stratified Rocks: These rocks posses planes of stratification or cleavage and such rocks can be easily split along these planes Ex: sedimentary rocks 

b. An stratified rocks: The structure may be crystalline granular or compact granular. Examples: Igneous rocks and Sedimentary rocks affected by movements of the earth. 

c. Foliated Rocks: These rocks have a tendency to split up in a definite direction only. Ex: Metamorphic rocks. 

III. Chemical Classification:

According to this classification rocks are classified into three types.

a. Siliceous rocks: In these rocks, silica is predominates. The rocks are hard; durable and not easily effected by weathering agencies. Ex: Granite, Quartzite, etc. 

b. Argillaceous Rocks: In these rocks, clay predominates. The rocks may be dense and compact or may be soft. Ex: slates, laterite etc. 

c. Calcareous rocks: In these rocks, calcium carbonate predominates. The durability to these rocks will depend upon the constituents present in surrounding atmosphere. Ex: Lime Stone, marble etc.

*Also read :  USES OF STONES/ ROCKS