1. Properties of Minerals

2. What is a mineral?
• A naturally occurring, inorganic solid that
has a crystal structure and a definite
chemical composition.
• More than 3,000 identified minerals.
• About 20 minerals make up most of the
Earth’s crust.

3. Characteristics of a mineral
1. Naturally occurring
2. Inorganic
3. Solid
4. Crystal structure
5. Definite Chemical composition.

4. Naturally Occurring
• Mineral must occur naturally on Earth
– Gold, copper, silver, graphite

5. Inorganic
• The mineral cannot arise from materials
that were once part of a living thing
• Coal occurs naturally in the Earth’s crust,
but it comes from the remains of plants
and animals that lived millions of years
ago.

6. Solid
• A mineral is always solid, with a definite
volume and shape.

7. Crystal Structure
• The particles of a
mineral line up in
a pattern that
repeats over and
over again.
• A crystal has flat
sides, called
faces, that meet
at sharp edges.

8. Definite Chemical Composition
• A mineral always contains certain
elements in definite proportions
– For example, the mineral of quartz has one
atom of silicon for every to atoms of oxygen.

9. How do we identify a mineral?
• Each mineral has its own specific
properties that can be used to identify it.
1. Hardness
2. Color
3. Streak
4. Luster
5. Density

10. Hardness
• In 1812, Friedrich Mohs, a mineral expert,
invented a test to describe and compare
the hardness of minerals.
• The scale ranks ten minerals from softest
to hardest.
• A mineral can scratch any mineral softer
than itself.

11. Mohs Hardness Scale

12. Color
• Color can be used to identify only those few
minerals that always have their own
characteristic color.
– Malachite is always green
– Azurite is always blue
• Many minerals, however, like quartz, can occur
in a variety of colors.

13. Streak
• A streak test can provide a clue to a
minerals identity.
• The streak of a mineral is the color of its
powder.
• You can observe a streak by rubbing a
mineral against a streak plate.

14. Luster
• Luster is the way a mineral reflects light
from its surface.
• Minerals containing metals are often shiny.
• Other minerals, such as quartz, have a
glassy luster.

15. Density
• No matter what the size of a mineral, the
density of that mineral always remains the
same.
• You must determine the mass of the mineral
(on a balance)
• You then place the mineral in water, to see
how much it displaces.
• The volume of the displaced water, equals
the volume of the mineral.

16. Testing Density
Rocks mass = 300 ounces
Displaces water by 100 cm3
So volume of rock must be 100
cm3
D = MU 300
V 100
D = 100 g/cm3