Chapter 2: Minerals and Rocks Study Guide
Section 2: Classifying Rocks
Key Idea: To study a rock sample, geologists observe the rock’s mineral composition, color, and texture.
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)
Texture




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

Erosion
the process by which running water, wind, or ice carry away bits of broken-up rock

Deposition
the process by which sediment settles out of the water or wind carrying it

Compaction
the process that presses sediments together

Cementation
the process in which dissolved minerals crystallize and glue particles of sediment
together
Chapter 2: Minerals and Rocks Study Guide
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
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.