Download Classifying Rocks

Name: ___________________________ Date: ___________________ Period: _____ Pg. #: ____
Classifying Rocks
Use your textbook (pages 146-149) to complete these notes and
answer the questions on the back.
When studying a rock sample, geologists observe the rock’s
___________________, ___________________, and ___________________.
Texture: The look and feel of the rock’s ___________________.
For example: Smooth and glassy, rough, or chalky
Grains: A particle of mineral or another rock that give a rock its texture.

Grain Descriptive Terms:
o Grain Size:

Coarse (___________________): Grains that can be seen
___________________ with or without a hand lens

Fine (___________________): Grains that can only be seen
with a ___________________.
o Grain Shape: Grains could vary greatly in ___________________.

Some Shapes: tiny, sand-like particles, small seeds,
exploding stars, ___________________, or jagged.
o Grain Pattern: Grains in rock often form in patterns.

Examples: Flat layers, ___________________, swirling
patterns, rows of multi-colored beads, or random patterns.
o No Visible Grain: Some rocks have ___________________
crystal grain because as the rocks formed, they
___________________ cooled and no ___________________
formed. This could give the rock a ___________________
appearance. Other rocks with a glassy appearance are made up of
small particles called silica (for example, flint).
Mineral ___________________: To determine the mineral composition inside a
rock, geologists will examine the crystal size and ___________________, note
reactions to ___________________, and determine whether a mineral is
magnetic.
Origin: How rocks ___________________.

Three major groups of rocks.
o ___________________ - cooling of molten magma or lava.
o Sedimentary – particles of other rocks or the remains of plants and
animals ___________________ together.
o Metamorphic – existing rock is changed by___________________,
pressure, or chemical ___________________ deep underground.
Section 1 Review: Answer with COMPLETE SENTENCES!!
1. What three characteristics do geologists use to identify a rock sample?
2. What are the three groups into which geologists classify rocks (3 rock types)?
3. What is a rock’s texture? List the 4 types of texture your book describes.
4. What methods do geologists use to determine the mineral composition of a
rock?