Download Section 4: Sedimentary Rocks

Chapter 2: Minerals and Rocks Study Guide
Section 1: Properties of Minerals
Key Idea: Each mineral has properties (characteristics) that can be used to identify it.
Color-observe the surface
Streak- the color of its powder
Luster- how light is reflected (e.g. metallic, glassy,
earthy, silky, waxy, pearly)
**Hardness-measured with the scratch test
**One of the most useful tests to identify minerals
Density-ratio of mass to volume
Crystal Structure- the number and angle of crystal
faces
Cleavage- splits along flat surfaces
Fracture- breaks apart in an irregular way
Moh’s Hardness Scale
 Diamond is hardest known mineral.
 Minerals can only scratch minerals that are softer
(e.g. a mineral with a hardness of 7 can scratch a 6, but not an 8)
 Elements, such as copper, gold, and silver, are minerals.
Section 2: Classifying Rocks
Key Idea: To study a rock sample, geologists observe the rock’s mineral composition, color, and texture.
Mineral Composition
 Rock-forming minerals are 20 minerals that make up most of the rocks in
Earth’s crust.
Granite
 Granite is made up of quartz, feldspar, mica, and horneblend.
Color
 Granite is a light-colored rock with high silica content.
*Color alone is not enough  Granite has larger crystals than basalt.
information to identify a
 Basalt is a dark-colored rock with lower silica content.
rock.
 Basalt is made up of small mineral crystals that cannot be seen with the
Basalt
naked eye.
Texture
 Grains (particles of minerals) make up the texture.
 Describes the look and feel of the rock using terms that are based on the
size, shape, and pattern of the grains.
o Size- coarse (large-easy to see), fine (small-seen with microscope)
o Shape- rounded, jagged
o Pattern- banded (pattern of layers), nonbanded (no pattern)
Section 3: Igneous Rocks
Extrusive Rock
Igneous rock that forms from lava on Earth’s surface (ex- means out)
Intrusive Rock
Igneous rock that forms from magma beneath Earth’s surface (in- means in)
Key Idea: Throughout history, igneous rocks have been used for tools and building materials.
 Igneous rocks are hard, dense, and durable.
Chapter 2: Minerals and Rocks Study Guide
Tools
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Rocks with rough textures, like pumice, are used for cleaning and polishing.
Native Americans used obsidian to make sharp tools.
Perlite is mixed with soil and used for starting vegetable seeds.
Building Materials
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Ancient Egyptians used granite to build statues.
Incas of Peru build fortresses from granite and other igneous rock.
In the early 1900s, the U.S. used granite to build bridges and public buildings.
Thin sheets of granite are used for curbstones and flooring.
Basalt can be used for cobblestones or as landscaping material.
Texture
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Rocks can have same mineral composition, but different texture.
Texture depends on size and shape of its mineral crystals.
Intrusive rocks have larger grains (slow cooling)
Extrusive rocks have smaller grains (rapid cooling)
*Porphyry is a type of rock that cools slowly and then quickly,
which results in large crystals surrounded by smaller crystals.
Section 4: Sedimentary Rocks
Sediment
small, solid pieces of material that come from rocks or living things (pebbles, mud, shells,
leaves)
Key Idea: Most sedimentary rocks are formed through a sequence of processes: weathering, erosion,
deposition, compaction, and cementation.
Weathering
the breaking up of rock due to freezing and thawing, plant roots, acid, and other forces
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Erosion
the process by which running water, wind, or ice carry away bits of broken-up rock
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Deposition
the process by which sediment settles out of the water or wind carrying it
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Compaction
the process that presses sediments together
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Cementation
the process in which dissolved minerals crystallize and glue particles of sediment
together
Key Idea: The three major groups of sedimentary rock are clastic rocks, organic rocks, and chemical
rocks.
Clastic Rock- sedimentary rock formed when rock fragments are squeezed together
 Clastic rocks are grouped by the size of the rock fragments they contain.
Conglomerate
Breccia
 Rock fragments with rounded
 Rock fragments with sharp edges
edges
Organic Rock- sedimentary rock formed where the remains of plants or animals are deposited in layers
Coal- Forms from the remains of swamp plants buried in water
Limestone*- Forms in the ocean where living things, such as coral, clams, and
oysters, have deposited hard shells and skeletons after they have died.
Chapter 2: Minerals and Rocks Study Guide
Chemical Rock- formed when minerals dissolved in a water solution crystallize, or from mineral deposits
left when seas or lakes evaporate.
Halite
 Rock salt forms by evaporation
Limestone*
 forms when calcite is dissolved in a solution, and then crystallizes
*Note: Limestone can be sedimentary or chemical. Either can be used to make cement.
Section 4: Metamorphic Rocks
Key Idea: Any rock that forms from another rock as a result of heat or pressure (or both) is a
metamorphic rock.
Heat and/or pressure can change:
 Shape
 Texture
 Composition
The change can be:
 Igneous to Metamorphic
 Sedimentary to Metamorphic
 Metamorphic to Metamorphic
Key Idea: The metamorphic rocks marble and slate are important materials for building and sculpture.
Marble is used for statues and buildings.
Slate is used for roofing, outdoor walkways, and
trim for buildings.
 Many colors
 Many colors
 Even grain
 Foliated-splits easily into flat pieces
 Can be cut into thin slabs
 Can be carved into many shapes
Section 6: The Rock Cycle
Rock Cycle the series of processes that slowly change rock from one kind to another
Key Idea: Forces deep inside the Earth and at Earth’s surface produce a slow cycle that builds,
destroys, and changes the rocks in the crust.
Rocks are changed, but material is NOT lost or gained.
Key Idea: There are many paths through the rock cycle.