Lab: Introduction to Minerals and Rocks

Learning Objectives
• Describe the basic mineral properties and identify common rock-forming minerals.
• Explain the rock cycle and the processes that form igneous, sedimentary, and metamorphic rocks.
• Distinguish among igneous, sedimentary, and metamorphic rock samples.

Introduction
The minerals identified in this lab represent a small collection of the most common rock-forming
minerals. To understand the relationship between minerals and rocks, think of a candy bar made up of
several different materials such as chocolate, sugar, nuts, and caramel. The minerals are the ingredients
(chocolate, sugar, nuts, caramel) that make up a rock (the candy bar). Minerals differ from each other in
chemical composition and structure. Rocks differ from each other based on the environmental setting in
which they formed. This lab will introduce you to the three families of rocks as well as the environment
and material needed to create them. You will learn how these rocks interact in what is known as the
rock cycle. And, you will learn the basics in mineral and rock identification by utilizing your observation
and interpretation skills.

Part A. Introduction to Minerals

A mineral must satisfy all four of the following criteria:
• Minerals are a naturally occurring substance (not made by humans),
• Minerals are an inorganic substance (not composed of living or once living organisms),
• Minerals have a fixed chemical composition (elements), and
• Minerals have an orderly internal structure (based on how the elements bond with each other).

Check It Out! How Many Minerals Are There?

There are approximately 4,000 different minerals found on Earth, and each of those minerals have a
unique set of properties. Some minerals are abundant, like quartz and beryl, like the Colorado State
gemstone aquamarine. Check out the Colorado Geological Survey website to learn more about the State
gemstone!

The vast majority of the minerals that make up the rocks of Earth’s crust are silicate minerals. These
include minerals such as quartz, feldspar, mica, amphibole, pyroxene, olivine, and a great variety of clay
minerals. Lighter-colored silicates are called felsic, as they lack iron and magnesium, while darker-
colored minerals are called mafic, as they do contain iron and magnesium. The building block of all of
these minerals is the silica tetrahedron, a combination of four oxygen atoms and one silicon atom. The
remaining minerals are non-silicate minerals, meaning that they do not have silicon as part of their
chemistry. Non-silicates include sulfides, oxides, native elements, sulfates, carbonates, and halides.
Often these minerals are formed in either sedimentary or metamorphic rocks.

Check It Out! Silicate vs. Non-Silicate Minerals

Watch a tutorial video on the differences between silicate and non-silicate
minerals, and learn how to identify the differences between these two types
of minerals. (Video length is 4:25).
Conflict Minerals
Some mineral mining operations fund violence and cause human rights abuses. You may have heard of
“blood diamonds” or “dirty gold” before. Conflict minerals are mined in locations with political
instability, corrupt governments, armed conflict, and/or lax regulations and then sold on the global
market; profits are used to perpetuate further violence and human rights abuses. By increasing the
funds of armed groups, mine profits increase fighting and spread violence. Conflict mineral violence has
been documented in numerous countries including Colombia, Myanmar (Burma), Côte d'Ivoire, and
other countries. A 2012 U.S. federal law requires companies to publicly disclose their use of the conflict
minerals that are the source of tantalum, tin, gold, and tungsten that originate in the Democratic
Republic of the Congo or a neighboring country. These four minerals are used in electronic products like
cell phones and laptops. Conflict minerals compose end-user products through a complex chain of local
and international traders, processors, and manufacturers.

Let’s take a closer look at the minerals that provide the metals identified in the 2012 law.
• The metal tantalum (symbol Ta) is found in the mineral tantalite. The chemical formula for
tantalite is (Fe, Mn)Ta2O6—either one iron atom or one manganese atom bonds with two
tantalum atoms, and six oxygen atoms. Tantalum is used in electronics as a capacitor.
• The metal tin (symbol Sn) is found in the mineral cassiterite. The chemical formula for cassiterite
is SnO2—one tin atom is bonded to two oxygen atoms. Tin is used as a sorter on circuit boards in
electronics.
• The metal gold (symbol Au) is often found in its elemental form as gold nuggets, as veins in
rocks, or in alluvial (river) deposits. Gold is used as a coating for electric wires in electronic
devices.
• The metal tungsten (W) is found in the mineral wolframite. The chemical formula for wolframite
is (Fe,MN)WO4—either one iron or one manganese atom bonds with one tungsten atom and
four oxygen atoms. Tungsten is used for electronic filaments and gives mobile phones their
vibrating capacity.

1. Select either tantalite, cassiterite, or wolframite and explain how this mineral meets the four
criteria of a mineral. Also indicate if the mineral is a silicate or non-silicate mineral.
Basic Mineral Properties
Minerals can be identified by their physical characteristics. The physical properties of minerals are
related to their chemical composition and bonding. Some characteristics, such as a mineral’s hardness,
are more useful for mineral identification. Color is readily observable and certainly obvious, but it is
usually less reliable than other physical properties. The five basic properties you will investigate for
mineral identification are as follows: color, streak, luster, hardness, and cleavage/fracture.

2. Using the photographed specimen below (Figure 12.1), answer the following questions:

a. What is the general color of the specimen?

b. What is the general shape (square, triangle, etc.) of the specimen?

c. Is the specimen shiny like glass, reflective like metal, or greasy like a candle?

d. If the specimen were dropped, do you think it would shatter or break into a geometric
design?

Figure 12.1: Fluorite Crystals

 Think About It…Why Is This Important?
The previous question provided you the general steps on identifying a mineral. It is
important to know that when asking critical and constructive questions it is best not to
make a judgment after the first questions. Following a set of rules or guidelines ensures
the best results. So, don’t jump to conclusions as you follow the instructions on how to
identify minerals and rocks in the upcoming exercises.

Color
For most of us, color is one of our key ways of identifying objects. While some minerals have particularly
distinctive colors that make good diagnostic properties, many do not. For many others, color is simply
unreliable. The mineral sulphur is always a distinctive and unique yellow. Hematite, on the other hand, is
an example of a mineral for which color is not diagnostic. In some forms hematite is deep dull red, but in
others it is black and shiny metallic. Many other minerals can have a wide range of colors (e.g., quartz,
feldspar, amphibole, fluorite, and calcite). In most cases, the variations in colors are a result of varying
proportions of trace elements within the mineral. In the case of quartz, for example, yellow quartz
(citrine) has trace amounts of ferric iron (Fe3+), rose quartz has trace amounts of manganese, purple
quartz (amethyst) has trace amounts of iron, and milky quartz, which is very common, has millions of
fluid inclusions (tiny cavities, each filled with water).

Search the Internet or use the QR codes/website links shown below to research mineral colors.
3. Identify four different variations or types of quartz, as well as their general color.
1. Variation 1 (name and color):

2. Variation 2 (name and color):

3. Variation 3 (name and color):

4. Variation 4 (name and color):

4. Identify four different minerals that can be green.

1. Mineral 1:

2. Mineral 2:

3. Mineral 3:

4. Mineral 4:

5. Identify four different minerals that can be blue.

1. Mineral 1:

2. Mineral 2:

3. Mineral 3:

4. Mineral 4:

6. Explain why although the most obvious tool for mineral identification is the color, it is not the
most accurate or definitive tool. Your response should be one to two sentences in length.
 Check It Out! Minerals in Fireworks!?

Minerals provide the colors for fireworks. Check out this link by the United
States Geologic Survey that identifies which minerals produce some of your
favorite colors in fireworks!

Streak
Streak is the color of a mineral’s powder. Streak is a more reliable property than color because streak
does not vary. Minerals that are the same color may have a different colored streak. Many minerals,
such as quartz, do not have a streak, as they are harder than the streak plate. To check the streak, you
must scrape the mineral across an unglazed white porcelain plate.

7. Observe the streak provided below (Figure 12.2). The photograph shows that the streak color is
similar although the specimen colors are not. These two samples are the same mineral, which is why the
streak plate color is the same, so why do you think the samples look different? Tip: read the Think About
It box below.

Figure 12.2: Examples of a Mineral's Streak.

Think About It…How Can These Samples Be the Same Mineral?

Hematite is a common iron oxide mineral, which means that this mineral can rust. The
name hematite is derived from the Greek word haima, meaning blood, which makes
reference to the mineral’s streak! Fun fact: hematite is used as a pigment in red paint and
is used in some makeups as a natural glitter!

Luster
Luster is the way light reflects off the surface of a mineral, and the degree to which it penetrates into
the interior. The key distinction is between metallic and non-metallic lusters. Light does not pass
through metals, and that is the main reason they look “metallic”. Even a thin sheet of metal—such as
aluminum foil—will prevent light from passing through it. Many non-metallic minerals may look as if
light will not pass through them, but if you take a closer look at a thin edge of the mineral you can see
that it does. If a non-metallic mineral has a shiny, reflective surface, then it is called glassy. If it is dull
and non-reflective, it is called earthy. Other types of non-metallic lusters are waxy (like a crayon or
candle) or pearly (like a shell). Luster is a good diagnostic property, since most minerals will always
appear either metallic or non-metallic.

Use the luster flow chart (Figure 12.3) to answer the following questions about the two specimens
pictured in Figure 12.4.

8. Sample A (Figure 12.4, left photograph):

1. What is the luster?

2. What is the color?

9. Sample B (Figure 12.4, right photograph):

1. What is the luster?

2. What is the color?

Figure 12.3: Metallic and Non-Metallic Luster Flow Chart.

Figure 12.4: Images of Two Unknown Samples.8

Check It Out! Mineral Luster

This lab simplifies luster to five options, but the Mineralogical Society of America
acknowledges 10 different types of luster!
Hardness
Mohs' scale of mineral hardness is named after Sir Friedrich Mohs, a mineralogist who invented a scale
of hardness based on the ability of one mineral to scratch another. According to the scale, talc is the
softest: it can be scratched by all other materials. Gypsum is harder as it can scratch talc but not calcite,
which is even harder. An easy benchmark to remember is that the human fingernail has a hardness of
about 2.5, so if you can scratch it with your nail, it must be softer than a 2.5. The hardness of a mineral
is controlled mainly by the strength of the bonding between the atoms and partly by the size of the
atoms. It is a measure of the resistance of the mineral to scratching. Mohs’ scale is for natural minerals.
Diamond is always at the top of Mohs’ scale, being the hardest mineral. There are ten minerals in Mohs’
scale (from softest to hardest): talc, gypsum, calcite, fluorite, apatite, feldspar, quartz, topaz, corundum,
and diamond (Figure 12.5).

Figure 12.5: Image of Minerals Used in the Mohs’ Hardness Scale.

Cleavage and Fracture

The way in which a mineral breaks is determined by the arrangement of its atoms and the chemical
bond between those atoms. It is difficult for us to observe these bonds, but we can observe the shape
and design into which minerals break. A mineral that exhibits cleavage will consistently break, or cleave,
along a parallel flat surface. Muscovite mica is a good example as it breaks along very closely spaced flat
planes that yield thin sheets. We would identify this as having one plane of cleavage (a plane represents
a flat surface with a top and bottom). If a mineral had six flat sides, we would say that the specimen has
three planes of cleavage. A helpful way of visualizing cleavage is with the use of an ax (Figure 12.6). An
ax makes a single cut, defining a top and bottom, so, if a specimen needs two axes, it would have two
directions of cleavage, and have four flat sides.
 Figure 12.6: Image of Mineral Cleavage.

Some minerals will be observed in a solid crystalline form. The arrangement of the atoms within the
mineral will determine the external shapes, and as the mineral begins to solidify, these microscopic
crystals, or seeds, will form and begin to grow. The longer the mineral has to form, the larger the crystal.
Other minerals fracture, which means that they break in a rough or irregular pattern. Some minerals,
such as quartz, will fracture along the surface and create a conchoidal fracture. A conchoidal fracture
does not have any surface planes like those seen in Figure 12.6.

Think About It…California Beach Sand?

Most of the sand that is found along California’s beaches are composed of quartz and
feldspar crystals. Quartz is known for its conchoidal fracture. Conchoidal fractures result
in a curved breakage, that resembles the gradual curves of a mussel shell, which is the
origin of the name! Next time you are at the beach, examine a quartz grain up close to
see its conchoidal fracture.

Now that you understand mineral cleavage and fracture, answer the following questions about the two
samples shown in Figure 12.7.

10. Sample A (Figure 12.7, left shape):

1. If you had to describe this sample as a shape, what shape would it be?

2. How many sides does this sample have?

3. How many planes or directions of cleavage does this sample have?

11. Sample B (Figure 12.7, right shape):

1. If you had to describe this sample as a shape, what shape would it be?

2. How many sides does this sample have?

3. How many planes or directions of cleavage does this sample have?

 Figure 12.7: Image of Two Shapes Exhibiting Cleavage.

Part B. Mineral Identification

Guided Practice: Mineral Identification

Go to this tutorial video from Professor Jeremy Patrich on how to identify

minerals based on their properties. (Video length is 7:27).

How to Use the Basic Mineral Identification Table

As you have learned up to this point, minerals have many physical properties. Table 12.1 provides
different properties of minerals organized by hardness (the softest minerals are at the top and the
hardest minerals are at the bottom). Remember that your fingernail has a hardness of 2.5. If a specimen
has most or all of the properties along a horizontal row, then the name of that sample is shown on the
far-left column.

Table 12.1: Basic Mineral Identification Table

Mineral Mineral Mineral Mineral Mineral Cleavage or Other

Name Hardness Color Luster Streak Fracture Properties
Talc 1 White to Waxy to White Cleavage: 1 Feels Slippery
Gray White Pearly Direction
Gypsum 2 Colorless Pearly White Cleavage: 1 Used in
to Direction Drywall
Brownish
Muscovite 2-2.5 White to Vitreous White Cleavage: 1 Is Elastic,
Mica Greenish (Glassy) Direction Peels into
Sheets
Galena 2.5 Light to Metallic Grayish- Forms in Perfect Is a Lead
Dark Gray Black Cubes Sulfide (Very
Dense)
Halite 2.5 White to Vitreous White Cleavage: 3 Salty in Taste
Pink Directions
(Square)
 Biotite 2.5-3 Dark Vitreous Gray Cleavage: 1 Is Elastic,
Mica Brown to to Pearly Direction Peels into
Blackish Sheets
Calcite 3 Clear, Blue, Vitreous White Cleavage: 3 Double
Pink, to Earthy Directions Refraction
Green, to (Rhombohedral)
Brown
Azurite 3.4-4 Blue Vitreous Light Blue Conchoidal Mammillary
to Earthy Fracture
Malachite 3.6-4 Green Vitreous Light Fracture is Copper Ore
to Waxy Green Uneven: Breaks
Flourite 4 White, Vitreous White Cleavage: 4 Glows When
Green, Octahedral (8 Exposed to
Yellow, to sides) UV Light
Red
Kyanite 4-6.5 Blue to Vitreous White Elongated or Fibrous and
Black or Pearly Bladed Crystals Flaky
Apatite 5 Lime Green Vitreous White Hexagonal Prisms Glows When
to Brown to Exposed to
Resinous UV Light
Hematite 5.5-6 Reddish to Metallic Reddish- Flaky Used as
Blackish Brown Glitter
(unless
oxidized)
Orthoclase 6 White to Vitreous White Cleavage: 2 Looks Like a
Feldspar Pink Blocky Broken Brick
Pyrite 6.5 Gold Metallic Greenish- Forms in Perfect Is a Lead
Black Cubes Sulfide (Very
Dense)
Olivine 6.5 Yellow Vitreous White Conchoidal Crystals Will
Green to Fracture Have 6 Sides
Green
Quartz 7 Clear to Vitreous White Conchoidal Crystals Will
Brown Fracture Have 6 Sides
Topaz 8 Clear to Vitreous White Conchoidal Used as a
Red Fracture Gemstone
Corundum 9 Red to Vitreous None None- Crystal is Extremely
Gray Hexagonal Hard

Mineral Identification Activity (Digital Version)

Your instructor will indicate which playlist (set 1, 2, or 3) you should use for this activity. Each playlist
begins with the Guided Practice video on mineral identification, followed by six mineral specimens. Click
on the correct QR code or link to access the playlist. Be sure to read the mineral properties shown in
the video details and use Table 12.1 to identify each specimen. Write your answers in question 12
below. Note: the mineral specimen videos provided in the playlists do not have audio.
Playlist 1: Playlist 2: Playlist 3:

Mineral Identification Activity: Your Answers

12. Identify the minerals.

1. Sample __________ (number or letter) is the mineral: _______________________

2. Sample __________ (number or letter) is the mineral: _______________________

3. Sample __________ (number or letter) is the mineral: _______________________

4. Sample __________ (number or letter) is the mineral: _______________________

5. Sample __________ (number or letter) is the mineral: _______________________

6. Sample __________ (number or letter) is the mineral: _______________________

Part C. Rocks and Their Properties

Rocks are naturally occurring aggregates of one or more minerals. The rock components of the crust are
slowly but constantly being changed from one form to another and the processes involved are
summarized in the rock cycle (Figure 12.8). The rock cycle is driven by two forces:
• Earth’s internal heat engine, which moves material around in the core and the mantle and leads
to slow but significant changes within the crust, and
• The hydrological cycle, which is the movement of liquid water, ice, and water vapor at or near
the surface of the Earth, and is powered by the Sun.

The rock cycle is still active on Earth because our core is hot enough to keep the mantle convecting, our
atmosphere is relatively thick, and we have liquid water. On some other planets or their satellites, such
as the Moon, the rock cycle is virtually dead because the core is no longer hot enough to drive mantle
convection and there is no atmosphere or liquid water.8
 Figure 12.8: The Rock Cycle.

13. Refer to Figure 12.8.

1. What types of rock form from the cooling of magma?

2. What are the four processes that create sediments?

3. What rock is formed when sediments are buried, compacted, and cemented?

4. What three arrows are pointing to the metamorphic rock box? Hint: these are the three
rock types that can be transformed into a metamorphic rock through burial, heat, and
pressure.

Igneous Rocks
Igneous rocks form when molten material cools and hardens. They may form either below (intrusive) or
above (extrusive) the Earth’s surface. They make up most of the rocks observed on Earth. Most igneous
rock is buried below the surface and covered with sedimentary rock, so we do not often see just how
much igneous rock there is on Earth. In some places, however, large areas of igneous rocks can be seen
at Earth’s surface.
A key to understanding the crystalline structure of igneous rocks depends on the rate of cooling. The
faster the material cools, the smaller the crystals. If the crystals or the minerals are so small that they
can not be identified with the naked eye, we call those aphanitic crystals (think microscopic organisms).
If the crystals are large, maybe the size of a pencil eraser, we call those porphyritic crystals.

Classifying Igneous Rocks

Igneous rocks are classified according to how and where they formed and what they are composed of. In
other words, igneous rocks are classified based on the following:
• whether or not they are plutonic (they cool and crystallize inside the Earth) or volcanic (they
cool and crystallize at the surface of the Earth), and
• what their mineral composition is; this is described as being felsic, intermediate, or mafic.

Intrusive igneous rocks crystallize deep beneath Earth's surface and if slow cooling occurs, then large
crystals can form. Some examples of intrusive igneous rocks are granite, gabbro, diorite, pegmatite, and
peridotite. Intrusive igneous rocks are also known as plutonic rocks.

Extrusive igneous rocks erupt onto Earth’s surface and they cool very quickly to form small crystals. In
fact, some cool so quickly that they can form into glass. Some examples of extrusive igneous rocks
include basalt, andesite, obsidian, pumice, scoria, rhyolite, and tuff. Extrusive igneous rocks are also
known as volcanic rocks.

Felsic is a term used to describe igneous rocks that are rich in elements that form quartz and feldspars.
An example of a felsic rock is granite. Mafic is a term used to describe igneous rocks that are rich in
magnesium and iron. An example of a mafic rock is basalt. Intermediate igneous rocks have
compositions between felsic and mafic.

Table 12.2 provides basic information to identify selected igneous rocks.

Table 12.2: Basic Igneous Rock Identification Table

Rock Intrusive or Rock Rock

Composition Other Properties
Name Extrusive Color Texture
Pumice Felsic Extrusive Cream to Glassy Will Float in Water
Gray (Frothy)
Obsidian Mafic Extrusive Dark Glassy Known as Nature’s Glass
Brown to
Black
Basalt Mafic Extrusive Gray to Aphanitic Earth’s Most Abundant
Black Rock
Scoria Mafic Extrusive Black to Aphanitic Similar to Basalt but Has
Deep Bubble-Like Cavities
Reds
Gabbro Mafic Intrusive Dark Phaneritic Most Abundant Rock of the
Green to Deep Oceanic Crust
Gray
Granite Felsic Intrusive Varies Phaneritic Oldest and Hardest Rocks
Known
Rhyolite Felsic Extrusive Pink to Aphanitic Silica-rich, Caused by Quick
Peach Cooling
 Diorite Intermediate Intrusive White Phaneritic Like a Dalmation, Large
and Black Spots of Feldspar and
Hornblende Minerals
Andesite Intermediate Extrusive Green to Aphanitic Usually Found on Earth’s
Dark Gray Surface above Subduction
Zones
Tuff Intermediate Extrusive Red to Fragemental From Large Volcanic
to Felsic Black Eruptions, the Settling
Materials Compact into
Cement

Check It Out! Igneous Rocks

This lab simplifies igneous rocks, but with some help from National Geographic, a lot more information
is available.

Sedimentary Rocks
Transportation is the movement of sediments or dissolved ions from the site of erosion to a site of
deposition; this can be by wind, flowing water, glacial ice, or mass movement down a slope. Deposition
takes place where the conditions change enough so that sediments being transported can no longer be
transported, like when a current slows. Lithification is what happens at depths of hundreds to
thousands of meters when those compacted sediments become cemented together to form solid
sedimentary rock.

Clastic Sedimentary
A clast is a rock or mineral fragment, ranging in size from less than a micron (too small to see) to as big
as an apartment block. Smaller clasts tend to be composed of a single mineral crystal, and the larger
ones are typically composed of pieces of rock. Most sand-sized clasts are made of quartz because quartz
is more resistant to weathering than any other common mineral. Most clasts that are smaller than sand
size are made of clay minerals. Most clasts larger than sand size are actual fragments of rock, and
commonly these might be fine-grained rock like basalt or andesite, or if they are bigger, coarse-grained
rock like granite or gneiss.

14. Refer to Table 12.1. What is the hardness of quartz? Do you think its hardness is one reason
why quartz is more resistant to weathering than other common minerals? Explain your response in at
least one sentence.

Chemical Sedimentary
Whereas clastic sedimentary rocks are dominated by components that have been transported as solid
clasts (clay, silt, sand, etc.), chemical sedimentary rocks are dominated by components that have been
transported as ions in solution.

The most common chemical sedimentary rock, by far, is limestone. Others include chert, banded iron
formations, and a variety of rocks that form when bodies of water evaporate. Biological processes are
important in the formation of some chemical sedimentary rocks, especially limestone and chert. For
example, limestone is made up almost entirely of fragments of marine organisms that manufacture
calcite for their shells and other hard parts, and most chert includes at least some of the silica tests
(shells) of tiny marine organisms such as diatoms.18 When these marine organisms die, their shells sink
to the seafloor. After a very long time, these shells are buried, compacted, and cemented into chemical
sedimentary rocks.

15. Is the sedimentary rock sample shown in Figure 12.9 clastic or chemical. How do you know?

Figure 12.9: A Sedimentary Rock.

Table 12.3 provides basic information to identify selected sedimentary rocks.

Table 12.3: Basic Sedimentary Rock Identification Table

Clastic or
Rock Name Rock Color Rock Texture
Chemical
Coquina Clastic Tan to Cream Medium to Coarse

Chert Chemical Varies Aphanitic

Coal Chemical Dark Gray to Black Banded, but Glassy

Shale Clastic Blue, Green, Gray Aphanitic (Mudstone)

Conglomerate Clastic Varies Coarse- Rounded

Breccia Clastic Varies Coarse- Angular

Siltstone Clastic Gray to Brown Coarse (Between Shale and

Sandstone)
 Limestone Clastic White, Blue to Coarse (Also Reacts to Acid)
Cream
Sandstone Clastic Varies Coarse

Travertine Chemical White to Brown Crystalline- Result of Mineral Springs

Check It Out! Sedimentary Rocks

This lab simplifies sedimentary rocks, but with some help from the National Geographic Society, we can
observe how sedimentary rocks are formed.

Metamorphic Rocks
Metamorphism is the change that takes place within a body of rock as a result of being subjected to
conditions that are different from those in which it formed. In most cases, but not all, this involves the
rock being deeply buried beneath other rocks, where it is subjected to higher temperatures and
pressures than those under which it formed. Metamorphism can also take place if cold rock near the
surface is intruded by rising magma. Metamorphic rocks typically have different mineral assemblages
and different textures from their parent rocks, but they may have the same overall composition.

Foliated
A rock that is foliated means that there is an observable layering or banding. Each layer can be as thin as
a sheet of paper or even a meter in width. Imagine such high pressure and temperature that the
minerals within a sample are realigned into a banded sequence! Imagine squishing a scoop of ice cream
between two cookies.

Non-Foliated
A rock that is non-foliated means that the rock does not have platy or sheet-like structure. These rocks
appear as a mass or large uniform piece, such as marble. Imagine such high pressure and temperature
that the minerals within a sample can not be aligned or moved. Think of squeezing saltwater taffy. No
matter how hard you squish it, the ingredients will never separate, it will just squish!

16. Does the metamorphic sample below (Figure 12.10) exhibit foliation or is it non-foliated? How
do you know?

Figure 12.10: A Metamorphic Rock.

Table 12.4 provides basic information to identify selected metamorphic rocks.

 Table 12.4: Basic Metamorphic Rock Identification Table

Rock What Was it

Foliated or Non-Foliated Rock Color
Name Before?
Marble Non-Foliated Varies Limestone

Schist Foliated Gray but Sparkles Shale- Mudstone

Quartzite Non-Foliated White, Pink, to Gray Sandstone

Anthracite Non-Foliated Black with Gold Luster Coal

Gneiss Foliated Black Stripes with White to Red Granite

Filling
Slate Foliated Purple to Black Shale- Mudstone

Phyllite Foliated- Splits Easily into Greenish to Black Shale- Mudstone

Sheets

Here is a fun fact: if shale (a sedimentary rock made of compacted clay minerals) undergoes continuous
metamorphism, it will transition into four different rocks the longer it undergoes metamorphism. Initially,
shale will metamorphose into slate. With increasing heat and pressure, it will then metamorphose into
phyllite, then into schist, and lastly into gneiss!

Check It Out! Metamorphic Rocks

This lab simplifies metamorphic rocks, but with some help from the National Geographic Society, we can
observe how metamorphic rocks are formed.

Part D. Rock Identification

How to Use the Basic Rock Identification Tables
The first step is to use the rock dichotomous key shown below to help determine the family of an
unknown rock, whether it be igneous, sedimentary, or metamorphic. You will then use the identification
tables to determine the name of the specimen (Tables 12.2, 12.3, and 12.4), which are broken into rows
and columns. If a specimen has most or all of the properties along a horizontal row, then the name of
that sample will be found in the first column on the left.

Rock Dichotomous Key

You can use the following steps to identify a rock sample.

Step 1: Can you see separate mineral crystals in the rock that are randomly intergrown?
• If yes, go to step 2.
• If no, go to step 7.

Step 2: Is the rock made up of just one kind of mineral?

• If yes, go to step 3.
• If no, go to step 4.

Step 3: If the rock has crystals of the same mineral, it is probably a metamorphic rock.

Step 4: Are the minerals in a banded or striped pattern?

• If yes, go to step 5.
 • If no, go to step 6.

Step 5. A rock that has a banded pattern is probably a metamorphic rock.

Step 6: A rock with minerals in a mixed pattern is probably an igneous rock.

Step 7: Is the rock full of small air pockets?

• If yes, go to step 8.
• If no, go to step 9.

Step 8: A rock with small air pockets is probably an igneous rock.

Step 9: Does the rock look like a piece of dark, broken glass?
• If yes, go to step 10.
• If no, go to step 11.

Step 10: A dark, glassy-looking rock is probably an igneous rock.

Step 11: Is the rock made up of flat plates or sheets?

• If yes, go to step 12.
• If no, go to step 13.

Step 12: A rock that splits easily into sheets is probably a metamorphic rock.

Step 13: Does the rock have particles in it, like sand, mud, or gravel?
• If yes, go to step 14.
• If no, go to step 15.

Step 14: A rock that is made of sediment (clay, sand, or pebbles) or fossils is a sedimentary rock.

Step 15: You have a hard rock to identify; try again, and study the rock more carefully before answering
each question.

Rock Identification Activity (Hands-On Version)

Using the tools provided, the dichotomous key shown above, and the abbreviated lists of common
igneous, sedimentary, and metamorphic rocks (Tables 12.2, 12.3, and 12.4), identify the samples
provided by your instructor. Write your answers in question 17 below.

Rock Identification Activity (Digital Version)

Your instructor will indicate which playlist (set 1, 2, or 3) you should use for this activity. Click on the
correct QR code or link to access the playlist. Use the dichotomous key shown above and the
abbreviated lists of common igneous, sedimentary, and metamorphic rocks (Tables 12.2, 12.3, and
12.4). Write your answers in question 17 below. Note: the videos provided in the playlist do not have
audio.

Playlist 1: Playlist 2: Playlist 3:

Rock Identification Activity: Your Answers
17. Identify the rocks.
1. Sample __________ (number or letter) is the rock: _______________________

2. Sample __________ (number or letter) is the rock: _______________________

3. Sample __________ (number or letter) is the rock: _______________________

4. Sample __________ (number or letter) is the rock: _______________________

5. Sample __________ (number or letter) is the rock: _______________________

6. Sample __________ (number or letter) is the rock: _______________________

7. Sample __________ (number or letter) is the rock: _______________________

8. Sample __________ (number or letter) is the rock: _______________________

9. Sample __________ (number or letter) is the rock: _______________________

10. Sample __________ (number or letter) is the rock: _______________________

11. Sample __________ (number or letter) is the rock: _______________________

12. Sample __________ (number or letter) is the rock: _______________________

Part E. Wrap-Up

18. Sketch a concept map that includes the key ideas from this lab. Include at least five of the terms
shown in bold-faced type.