Rocks and Minerals
Lesson 10 Rocks
1. The age of the Earth-
The Earth is about 4.6 billion years old.
2. How the layers cooled-
As the Earth cooled the heaviest and densest materials sank to the center, and the
lightest materials rose to the top. The heaviest materials are the metals iron and
nickel, which makes up the inner and outer cores. The lightest materials are rock
and make up the crust and upper most region of the mantle.
Rocks are composed of two or more minerals. These minerals have been 1) cemented
together 2) squeezed and heated together, or 3) melted and cooled together
Rocks make up the vast majority of the Earth's crust. The two most common rocks on
the crust are granite and basalts.
A mineral is a solid that is composed of one substance that occurs naturally on Earth.
Soil is composed of very small, weathered fragments of rock along with organic (decomposed
or decomposing plant and animal material) material.
6. Rock Cycle-
The rock cycle is the process in which igneous, sedimentary, and metamorphic rocks
are changed over time. Igneous rocks are formed by volcanic activity. Metamorphic
rocks are igneous, sedimentary, or other metamorphic rocks that have been changed
by heat, pressure, chemical means, or a combination of all or some of the above. Sedimentary
rocks are formed from the weathering of all of the rock types and the cementing,
compressing, or recrystallization of the sediments.
Granite is an igneous rock that has formed deep under the surface of the Earth. It
is composed of four minerals. They are 1) quartz 2)feldspar 3) mica 4) hornblende.
Feldspars are the most abundant minerals found on the surface of the Earth. Feldspars
can be glassy white, pink, and a variety of other colors. They contain silica, aluminum
and potassium. Clays are usually composed of weathered feldspar.
Micas are minerals that can be split into very thin sheets. Mica can be clear to
very dark green or black in color. Muscovite and biotite are the two micas we are
going to study.
Hornblende is a mineral that is composed of magnesium, iron, silica, and aluminum.
It is found in many igneous rocks.
Quartz is a very common mineral that is found on the surface of the Earth. Its chemical
formula is SiO2 (silicon oxide) Sand is quartz crystals that have been weathered
into small pieces.
Lesson 11 Minerals
A mineral is a solid material, made of one substance, that occurs naturally on Earth.
A crystal is a solid that forms by repeated 3-dimensional patterns of atoms, ions,
Amorphous-Minerals that do not grow in regular crystalline patterns
Crystalline- Minerals that grow in regular crystalline patterns.
A substance that is made of atoms that have an identical number of protons and electrons
and can not be reduced into a simpler form.
Characteristics of minerals that helps scientists to identify and label minerals.
a. Mohs Hardness Scale-
A scale that ranks the minerals relatively from 1-10. ! is the softest mineral (Talc)
and 10 is the hardest mineral (Diamond)
The way a mineral reflects light.
The color of a mineral as seen by the human eye. Streak is the color of the powder
of a minerals caused by rubbing the mineral across a streak plate. This shows the
true color before the mineral is attacked by the atmosphere.
Property of a mineral that is relative to other objects and minerals.
Lesson 11 vocabulary continued
A property of attraction between the mineral and a magnet. There are only two minerals
that are naturally magnetic.
The ability of a mineral to break along straight lines. Fracture is the ability of
a mineral to break or shatter like glass with no pattern or design.
A mineral that is high in iron. It is the most common form of iron ore. It is brown
to red in color. It has a metallic or earthy luster. It is a 5 on the Mohs hardness
Calcite is a mineral that is composed of Calcium Carbonate. It forms from the decomposition
fish skeletons or shell at the bottom of the ocean. It is usually yellow or yellowish
white in color. It is soft with a hardness of 2. It forms in perfect rhomboidal
cubes. It is the cementing agent of many sedimentary rocks. It is the substance
that forms stalactites and stalagmites in caves.
Talc is the soft mineral that is given he number 1 on Mohs Hardness scale. It has
pearly luster and is greasy tot he touch. It has perfect cleavage and was ground
up into talcum powder for many years.
Galena is a mineral with perfect cubic crystals. It is the main source of lead ore
in the U.S. It has a hardness of 2.5 making it quite soft..
Magnetite is a mineral that is almost pure iron. It is one of two minerals that is
magnetic by nature. It is a very good source of iron ore.
It has a metallic luster and is a 5.5 on Mohs hardness scale.
Lesson 12 Igneous Rocks
The word igneous comes to us from the Latin word "ignis" which means "fire"
Magma is molten rock that is located under the surface of the Earth.
This is an igneous rock that had cooled inside the Earth.
This is a very large igneous intrusive that is more than 100 square miles in volume.
It is the largest of the igneous intrusions. They usually have granite cores.
Batholiths are examples of igneous bodies that are called discordant bodies.
This is an igneous intrusion that runs vertically or near vertically and cuts across
a preexisting body of rock.
This is a smaller version of a batholith that runs parallel to an already existing
This is an igneous body that is similar to a dike with the exception that it runs
parallel to preexisting rock bodies instead of cutting through it.
These are igneous bodies that cool on the surface of the Earth.
This molten rock that has erupted to and on the surface of the Earth.
4. Acidic Rocks-
These are igneous rocks that are high in silica and are acidic in nature. Above 65%
vocabulary page 6
5. Basic Rocks-
These are igneous rocks that are much lower in silica than are acidic rocks. Below
This is the most widespread of all the extrusive igneous rocks. Basalts are dark
in color and are very fine-grained. Basalt minerals are so fine that they are not
able to be seen with the naked eye.
They usually cool very fast on the surface of the Earth but can cool inside the Earth.
This is a very light extrusive igneous rock. It is so light that it actually floats
on water. It forms in the air as it is shot out during a volcanic eruption. As the
lava flies through the air, the gases inside the lava escape and that leaves holes
in the rock.
Rhyolite is the same as granite in its composition. The difference is that rhyolite
forms on the surface of the Earth and cools much more rapidly. This leaves it with
This igneous rock is also similar to granite and rhyolite in its composition. It
is very dark in color.
This igneous rock is also called volcanic glass. It cools so rapidly that it does
not give the mineral crystals time to grow. It is very hard and fractures like glass.
It was used by ancient native peoples around the world for spear and arrow heads.
It can be clear to very dark green almost black in color.