LESSON 3: MATERIALS

OF THE EARTH
Minerals THREE MAIN CATEGORIES OF ROCKS
- Mineralogy is the study of minerals.
- Minerals are the building blocks of rocks. 1. Igneous Rocks – formed by the cooling and
- Formed in nature, formed in natural geologic formed by cooling and crystallization of hot,
processes. molten rock material called magma.
- Generally inorganic crystalline solid. - Igneous means “formed by fire”
- it makes up about 95% of the Earth’s crust.
Physical Properties of Minerals - When molten rock reaches the surface, it is called
Scientist identify more common minerals by their color lava
or appearance; others include their taste, smell, feel, - Igneous rocks are subdivided into 2 categories:
and sound.  Intrusive (emplaced in crust) the magma
The physical properties that can be testes are: that does that reach the surface and
 Luster - Refers to the way light is reflected from crystallized at great depth.
a mineral surface.  Extrusive when lava solidifies (extruded in to
 Hardness - Refers to the minerals resistance to earth surface of land or ocean bottom - the
being scratched. cooling molten material is called lava).
 Strreak - Refers to the color of the powdered
mineral 2. Sedimentary Rocks
 Cleavage - It is the tendency of the minerals - most common in the uppermost portion of the
to break along planes of weak bonding. crust.
 Fracture - Refers to the minerals that do not
- derived from the word sedimentation which
exhibit cleavage are said to fracture when
means “settling” of a material from a fluid.
broken
 Specific Gravity – Is a number which - Composing only 5% in the earth’s crust.
represents the ratio to the weight of an equal - Sedimentary rocks are those that are deposited
volume of water. and lithified (transformed.
- Common examples: Sandstone, chalk, limestone
Chemical Properties of Minerals
 Fizz Test - Test that used hydrochloric acid
3. Metamorphic Rocks
giving off bubble’s dioxide gas.
 Taste Test - Some minerals are tested as NaCl - formed under conditions of heat and pressure
(common table salt). similar to the environment in which igneous
formed.
- Metamorphic rocks change while the rock is still
ROCKS solid.
Geology – the study of the earth’s natural materials - Common examples: Slate, Marble, Quartzite
and processes including the earth’s atmosphere,
oceans and weather. It begins with the investigation
of rocks and minerals. Rock Cycle
Petrology – study of rocks.
Rocks are dependent on what process they will
Properties of rocks undergo. It is weathering and erosion then you can
 Rocks exhibit different properties. As to color, produce sediments turn into sedimentary rocks if they
rocks may be dark, light, reddish, gray, brown, compacted and cemented to each other.
yellow or even black.
If the rocks undergo heat and pressure, you will
 Rocks differ in texture, some are fine, some are
probably have a metamorphic rock. If metamorphic
rough.
rocks melts and cooled later on, igneous rocks formed.
 Some are glossy in appearance and smooth
to touch.
 Most rocks are hard, others are brittle.

Prepared by:

CHRIS JAMES E. GOLEN

Teacher

Reference: Salandanan G. Faltodo R. and Lopez M. Earth And Life Science: DIWA Learing Town