This document discusses minerals, their properties, and types. It defines a mineral as a naturally occurring inorganic substance with a definite chemical composition and atomic structure. Minerals are divided into rock-forming and ore-forming types. Rock-forming minerals are common in Earth's crust while ore-forming minerals have economic value. Common rock-forming mineral groups include oxides, carbonates, sulphides, sulphates, chlorides, and silicates. The document outlines several physical properties used to identify minerals, such as color, streak, luster, hardness, cleavage, and fracture. It also explains Mohs hardness scale and provides examples of different luster and fracture types.

1. Somali National University
Lecturer:
Abdirahman M.abdi
B.sc,M.sc geology (Int)

2. Minerals and their
Properties
Lecture-03

3. Minerals
• Definition:
• A mineral is naturally occurring
inorganic substance which has a more or
less definite chemical composition, and
definite atomic structure.

4. Types of Minerals
• The mineral may be divided into two groups
1- Rock-forming minerals,
2- Ore-forming minerals.
-Rock-forming minerals: Rock forming minerals are
those which are found in abundance in the rock of
earth crust.
- Ore-forming minerals: are those which are economic
value, and which do not occur in abundance in rocks.

5. Rock-Forming Minerals
• Approximately 3000 different minerals are
known, but most of them are rare.
• The minerals which occur in common
rocks are small number and they are
divided into the following groups.

6. 1- Oxides: Quartz, Magnetite, Hematite, Limonite.
2- Carbonates: Calcite, Dolomite, Siderite.
3- Sulphides: Pyrite, Galena, Sphalerite.
4- Sulphates: Gypsum
5- Chlorides: Rocksalt.
6- Silicates: Felspars, Mica,Augite, Olivine.

7. Identification of Minerals
Common minerals can be identified readily,
if their ordinary physical properties are
known.
These include such properties as color,
streak, luster, hardness, cleavage, fracture
Specific gravity, tenacity, odor.

8. Physical Properties of Minerals
1. Color: Some minerals possess
a characteristic color.
e.g. lead gray of galena, the black of
magnetite and green of chlorite.
2. Streak: Streak is the color of mineral powder.
The minerals are rubbed against unglazed
porcelain plate ( called streak plate)
e.g. pyrite is brass yellow and its streak is dark green

9. 3. Lustre: Lustre is the appearance of a
mineral surface in reflected light.
Types of Lustre:
I) Metallic lustre: it is the lustre exhibited by
metals, e.g. pyrite, galena,etc.
II) Vitreous lustre: it is the lustre exhibited
by the broken surface of glass, e.g. quartz.

10. III) Pearly lustre: it is the lustre exhibited by
pearls, e.g. mica.
IV) Siky lustre: it is the lustre exhibited by
silk fibers, e.g. asbestos.
V) Resinous lustre: it is the lustre exhibited
by resin, e.g. sphalerite, serpentine etc.

11. VI) Adamantine: it is the lustre exhibited b
diamonds.
VII) Dull or Earthy lustre: Minerals which
have no lustre are described as dull or
earthy, e.g. kaoline

12. 4.Hardness
Friedrich Mohs, a German mineralogist, developed
the scale in 1812. He selected ten minerals of
distinctly different hardness that ranged from a very
soft mineral (talc) to a very hard mineral (diamond).
With the exception of diamond, the minerals are all
relatively common and easy or inexpensive to obtain

13. • 1-Talc 6-orthoclase.
• 2-Gypsum 7- Quartz.
• 3-Calcite 8- Topaz
• 4-Fluorite 9- Corundum
• 5-Apatite 10- Diamond

14. • 5- Cleavage: it is the property of minerals.
to break more easily with smooth surfaces
in certain directions.

15. 6- Fracture: the nature of a broken surface
of a mineral is known as fracture, but the
breaking should be in any other direction
than the cleavage.

16. Types of Fracture:
I) Uneven fracture: when the broken surface is rough or irregular, e.g.
apatite
II) Even fracture: when the mineral break with a flat surface, e.g. flint
III) Conchoidal fracture: when the mineral breaks with curved surfaces.
IV) Hackly fracture: when the broken surface small sharp irregularities
like broken metal,
e.g. native copper

17. Review Questions
Q01: Describe a minerals?
Q02: what are the properties of minerals?
Q03: List it types of rock forming minerals?
Q04: Explain Moh’s hardness Scale?
Q05: what are the types of fracture?
Q06: Define a luster? And also its types?
Q07: what kind of luster has diamond?
Q08: who is the 5th mineral in hardness scale?
Q09: who is the 9th mineral in hardness scale?

18. •Thanks
The End