Lesson 1: Minerals
A. What is a mineral?
1. A naturally occurring, inorganic solid with a definite chemical composition and a
crystal structure is a(n) mineral.
a. Substances that are made by people are not minerals because they do not form
naturally.
b. Materials that contain carbon and once were alive are organic, whereas minerals
are not organic and cannot have once been alive.
c. No minerals are liquid because, by definition, minerals are always solid.
d. All minerals have a(n) crystal structure, which means the atoms are arranged in
an orderly, repeating pattern; this causes minerals to often have sharp edges and
smooth faces.
e. A mineral is always made of specific amounts of specific elements; therefore,
minerals always have a(n) chemical formula.
2. Minerals form from atoms that have been part of a(n) liquid. The atoms form an
orderly, repeating pattern by the process of crystallization, which can happen in
two main ways.
a. Minerals can crystallize from magma, which is melted rock.
b. Substances that dissolve in water can reform crystals when the water evaporates
or cools.
B. Mineral Identification
1. Each mineral has a unique set of physical properties, or characteristics, that can be
used to identify the mineral.
2. If you have two mineral samples of the same size, the mineral with the higher
density will feel heavier than the mineral with the lower density.
3. You can measure the hardness of a mineral by observing how easily the mineral
scratches or is scratched by other minerals.
a. The Mohs hardness scale ranks minerals from 1 to 10.
b. The hardest mineral is diamond, which measures 10 on Mohs hardness scale; the
softest mineral is talc, which measures 1 on Mohs hardness scale.
T2 Minerals and Rocks
4. Each mineral has a unique streak, which is the color of the mineral’s powder.
a. A mineral’s streak can be observed by scratching the mineral across a tile of
unglazed porcelain.
b. A mineral’s color and its streak sometimes differ.
5. The way the surface of a mineral reflects light is called the mineral’s luster.
6. A mineral displays cleavage if it breaks along smooth, flat surfaces.
7. A mineral’s crystal shape is determined by its atomic structure; large crystals can be
useful for identifying a mineral.
8. Some minerals have unusual properties, such as magnetism (the ability to attract
ironand steel), electrical conductivity, double refraction, or fluorescence (the ability
to glow under ultraviolet light).
9. Many common items are made of metals, which combine with other elements and
form minerals; these minerals are usually processed from ores, which are deposits of
metallic or nonmetallic minerals that be processed for a profit.
Lesson 2: Rocks
A. What is a rock?
1. A rock is defined as a naturally occurring solid mixture composed of minerals,
organic matter, glass, smaller rock fragments, or any combination of these.
2. The individual particles in rocks are called grains; they give clues about how the
rock formed.
B. Classifying Rocks
1. Rocks are classified based on how they form.
2. There are three main categories of rocks: igneous rocks, sedimentary rocks, and
metamorphic rocks.
3. Most rocks on Earth are igneous rocks.
a. Igneous rock forms from molten rock, which is called magma when it is below
Earth’s surface and lava after it erupts onto Earth’s surface.
b. As the molten rock cools, crystals of minerals start to grow; these become the
grains of newly forming igneous rocks.
c. Lava at Earth’s surface cools quickly, so the crystals that form are small; geologists
describe the texture of igneous rocks with small crystals as fine-grained.
d. Magma that is deep below Earth’s surface cools slowly, so the crystals that form
have time to grow large. Geologists describe the texture of igneous rocks with
crystals of this size as coarse-grained.
4. Rock and mineral fragments that are loose or suspended in water are called
sediment and are the source material for sedimentary rock.
a. The process by which sediment becomes sedimentary rock is called lithification.
b. The grain shape of igneous rocks can be described as rounded or angular.
5. One kind of rock forms when other types of rock are changed due to extreme high
temperatures and pressure. The original rock is called parent rock; the resulting rock
is metamorphic rock.
a. In the process of metamorphism, parent rock is squeezed, heated, or exposed to
hot fluid.
b. One characteristic of many metamorphic rocks is foliation—the process by which
flat minerals line up due to uneven pressures being applied to the rock, giving
these rocks, such as gneiss, a layered appearance.
C. Rocks in Everyday Life
1. Granite is a(n) igneous rock that is hard and durable, which makes it useful for
constructing structures such as fountains; pumice is a soft igneous rock that
contains hard glass, which makes it useful for polishing and cleaning.
T4 Minerals and Rocks
2. Sedimentary rocks, such as sandstone and limestone, are naturally layered, and so
they make good building stones; limestone is a(n) sedimentary rock that is used to
make cement.
3. Metamorphic rocks that are foliated split into flat pieces; for example slate is used
as a durable, fireproof stone for roofing; marble is a(n) metamorphic rock that is
soft enough to carve for in detailed sculptures
Lesson 3: The Rock Cycle
A. What is the rock cycle?
1. Recycling of rock material occurs naturally on Earth.
2. The rock cycle is the series of processes that continually change one rock type into
another.
B. Processes of the Rock Cycle
1. The formation of minerals or rocks are key processes of the rock cycle.
2. Igneous rock forms from melted rock that is on or below Earth’s surface.
a. Extrusive rock forms when lava erupts, cools, and crystallizes on Earth’s surface.
b. Intrusive rock forms when magma cools and crystallizes inside Earth.
c. Both extrusive and intrusive rock are igneous rock.
3. Uplift is the process that moves large amounts of rock up to Earth’s surface and to
higher elevations.
4. Uplift is driven by the movement of tectonic plates and is related to the building
of mountains.
5. At Earth’s surface, rock is subject to the environment.
a. Rock is weathered by wind, rain, glaciers, and the activities of some organisms
(or living things); these processes break down exposed rock into sediment.
b. Sediment is moved by erosion—the process by which glaciers, rain, and wind
carry sediment to low-lying places called basins.
6. The process of laying down sediment in a new location is called deposition; over
time, deposition causes layers of sediment to form, one on top of the other.
7. In the process of compaction, the weight of upper layers of sediment on lower
layers of sediment pushes the grains of the bottom layers closer together.
a. There are tiny spaces called pores between the grains of sedimentary rock.
b. When there is water containing dissolved minerals in the pores between
sediment, the minerals can crystallize, which helps cement the grains together
in sedimentary rock.
8. Below Earth’s surface, rocks are sometimes subject to high temperatures and
pressures, which cause them to undergo metamorphism.
a. With high enough temperatures, the metamorphic rock can melt and become
magma.
b. When the magma cools and solidifies, igneous rock forms, and another turn of
the rock cycle begins.
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9. The movement of Earth’s tectonic plates helps drive the rock cycle.
a. Volcanoes form near plate boundaries, giving rise to igneous rock; this kind of
rock also forms where plates move apart.
b. Rocks near colliding plates are often exposed to high pressure, which causes them
to undergo metamorphism.
c. When plates collide, one plate can get pushed deep below Earth’s surface, where
the rock melts and becomes magma; in time, it is likely to become igneous rock.
d. Colliding plates can push rock to Earth’s surface; such rock is subject to erosion,
which breaks the rock into sediment. These pieces of rock can eventually form
sedimentary rock.