Physical properties of rocks

1. Physical Properties of Rocks
Luqman Ahmed
Department of Earth Sciences
University of Sargodha, Sargodha,
Pakistan

2. Physical Properties of Rocks
Rock
• A Rock material is an aggregate of mineral particles
• Sedimentary, metamorphic, igneous rocks
Physical Properties
• The performance of rock, under a particular condition
depends upon physical and mechanical properties of rock
materials
• The physical properties may be known as index properties,
which describes the rock material and helps in classifying
them
Mechanical Properties
• The mechanical properties may be known as strength
properties and they will give an information about the
performance of rock materials, when subjected to a particular
loading system.

3. Physical Properties of Rocks
• Mineralogical composition, structure, and texture;
• Specific gravity G
• Unit weight/ Density
• Void ratio e
• Porosity n
• Moisture content w or m
• Degree of saturation, S
• Coefficient of Permeability K
• Electrical and Thermal Properties
• Swelling
• Anisotropy
• Durability

4. MINERALOGICAL COMPOSITION
Main Minerals in all three types of rocks
(Sedimentary, Metamorphic and igneous rocks)
• Quartz
• Feldspar
• Mica
• Homblende (Amphiboles)
• Pyroxene
• Olivine
• Calcite
• Kaolin, and
• Dolomite
Significance of Mineral Composition
• Physical Properties
• Mechanical Properties
• Hard rocks/ soft rocks

5. ROCK STRUCTURE & TEXTURE
The makeup of rocks from minerals and mineral aggregates.
Texture
Texture is determined by the dimensions, shape, and interrelationships of
the minerals.
 Grain size distribution
 Fine grained, medium grained, coarse grained
 Uniformly grained, well-graded, etc.
Porosity, Permeability, density, etc.
Structure
structure depends on the general features and spatial arrangement of the
larger
components of the rock
 Massive (No discontinuities), lamination, bedding, shearing, etc.

6. DENSITY, UNIT WEIGHT & SPECIFIC GRAVITY
Density
Mass per unit volume.
𝜌 =
𝑚
𝑉
 Units: g/cm3 , Kg/m3
 Dry Density,
 Bulk Density
 Standard Density
What density gives?

7. DENSITY, UNIT WEIGHT & SPECIFIC GRAVITY
Unit weight
Weight per unit volume
 𝛾 =
𝑊
𝑉
=
𝑚𝑔
𝑉
= 𝜌𝑔
 Units: kN/m3
 Water 9,800 N/ m3 or 9.81 kN/m3

 Specific gravity
 Ratio of the density of solids to the density
of water.
 𝐺 =
𝜌𝑠
𝜌𝑤
 SP is also called Relative Density