Types of Rock

It is very important for an engineer, a contractor and may be an architect to become conversant thoroughly with different types of building materials, their properties and their uses for different purposes. The correct uses of materials result in better structural strength, functional efficiency and esthetic appearance.
Building stones are obtained from rocks occurring in nature.
So, as a part of a series of different types of building materials, their properties and purposes of their uses, today I’m going to share the types of rock.
Rocks can be classified in following ways-

1.      Geological classification
2.      Physical classification
3.      Chemical classification

Igneous rock

1. Geological classification: As per geological classification rock types are-

1a. Igneous rocks: When hot magma from the earth’s lithosphere is cooled and solidified then Igneous rock is formed.
Example–Granite, Basalt and Dolerite etc.

1b. Sedimentary rocks: This type of rocks are formed when organic matter, sediments or chemical precipitates are somehow compacted together and solidified.
Example–Gravel, Sand Stone, Limestone, gypsum and lignite etc.

1c. Metamorphic rocks: when Igneous and Sedimentary rocks are changed in character due to pressure and temperature then metamorphic rocks formed. These rocks are found deep within earth.
Example–Quartzite, schist, slate, marble etc.

Metamorphic rock

2. Physical classification: This type of classification is based on general structure of rocks. According to this classification the rocks are classified into three types–

2a. Stratified rocks: These rocks possess planes of stratification or cleavage and can be easily split up along the planes. This type of rocks show a layered structure in their natural environment.
Example-Gravel, Sand Stone, Limestone, Gypsum etc.

2b. Unstratified rocks: The structure of this type of rocks may be crystalline or granular. This type of rocks don’t show any sign of strata.
Example-granite and marble.

2c. Foliated Rocks: Foliated rock is a metamorphic rock that has layers. In other word, when a metamorphic rock’s texture is somehow arranged in planes that is called foliated rocks.
Example-metamorphic rocks.

3. Chemical classification: This class of rocks are also three types-

3a. Siliceous rocks: Silica predominates in this rocks. These kind of rocks are hard and durable.
Example-Granite, quartzite etc.

3b. Argillaceous rocks: Clay predominates in this rock.
Example-Slates, Laterites etc.

3c. calcareous rocks: In this type of rocks, calcium carbonate predominates. Durability of this type of rocks depends upon the constituents present in surrounding atmosphere.
Example-Lime stone, Marble etc.

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