Laboratory Manual for Introductory Geology 4e

LEARNING
OBJECTIVES
■ Understand what makes
minerals different from other
materials
■ Become familiar with and
learn to describe the physical
properties of minerals
■ Identify the most common
rock-forming minerals using a
systematic approach
■ Recognize the economic value
of minerals
■ Learn what minerals can reveal
about Earth processes and
Earth history
MATERIALS
NEEDED
■ Sets of mineral and rock
specimens
■ Hand lens, streak plate, glass
plate, knife or steel nail, and
a penny to determine the
physical properties of minerals
■ Dilute hydrochloric acid (HCl)
for a simple chemical test
■ Small magnet
3.1 Introduction
This chapter begins our study of the materials of which the Earth is made. It starts by
examining the different kinds of materials in the geosphere, then focuses on minerals,
the basic building blocks of most of the Earth. You will learn what makes minerals
different from other substances; become familiar with their physical properties,
and use those properties to identify common minerals. Minerals are important to
geologists because they record the conditions and processes of ancient Earth history,
and to society because many are natural resources that contribute trillions of
dollars annually to the U.S. and global economies.
3.2 Classifying Earth Materials
Imagine that an octopus is swimming in the ocean when a container falls off a freighter
overhead, breaks up, and spills its entire cargo of sneakers, sandals, flip-flops, shoes,
moccasins, and boots into the sea. The octopus is curious about these objects and wants
to learn about them, but it doesn’t have heels or toes, doesn’t walk, has eight legs,
doesn’t understand “left” and “right,” and doesn’t wear clothes. How would it begin to
study these totally alien objects? A first step might be to sort, or classify, the objects into
subgroups of objects sharing similar features. But what kind of system would it use? One
possibility might be to separate items that are mostly enclosed (shoes, boots, sneakers,
moccasins) from those that are open (sandals, flip-flops). Another might be to separate
objects made of leather from those made of cloth; or brown objects from black objects;
or big ones from small ones. There are many ways to classify footwear, some of which
might lead our octopus to a deeper understanding of the reasons for these differences.
Seventeenth-century scientists faced a similar task when they began the modern
study of Earth materials. They started by describing and classifying these materials
because classification reveals similarities and differences between things that lead to
an understanding of the processes that formed them. Biologists classify organisms,
art historians classify paintings, and geologists classify Earth materials. Exercise 3.1
leads you through the thought processes involved in developing a classification
scheme for Earth materials.
EXERCISE 3.1
Classifying Earth Materials
Name:
Course:
Section:
Date:
(a) Examine the specimens of Earth materials provided by your instructor. Group them into categories you believe are
justified by your observations, and explain the criteria you used to set up the groups.
Group Defining criteria for each group Specimens in group
(continued )
54 CHAPTER 3 MINERALS