Geology 2 – Physical Geology Lab
Labs #3 and #4 – Mineral Identification (2 week lab)
Student Outcomes:
 Understand the various physical properties of minerals
 Be able to identify minerals by recognizing and systematically observing their distinctive physical
properties
 Be able to identify and name each of the 18 minerals samples listed in Part II by observing their
distinctive physical properties
 Recognize that physical properties of minerals may vary from sample to sample of the same mineral
 Understand and be able to apply the Mohs Hardness Scale
 Be able to identify and name the California State rock
 Know the minerals common in each of the three major rock groups
Materials:
 Part 1 - Eleven stations with mineral samples exemplifying key physical properties
 Part II - 18 mineral samples – required minerals for identification
 Part III – Mineral Identification – 10 mystery minerals to identify
 Hand lenses
 Hardness test kits
 HCl acid
 Student textbook with the descriptions of the mineral properties used to identify minerals
Logistics: The lab is in three parts, which you will have two weeks to complete;.
Part I - Move around the room to various stations at which you will observe excellent examples of
all of the physical properties. Each of the mineral samples exemplifies one or more of the key
physical properties used to identify minerals.
Part II - See examples of all the required minerals for identification along with descriptions of their
distinctive physical properties. A list of required minerals for identification is on page 4.
Part III - Determine the names of nine unknown minerals by observing their physical properties and
the identification key provided. Part III is the only part of the lab that will be graded.
Part I. Examples of physical properties of Minerals
Physical properties of minerals are the common visible and tangible characteristics used in the
identification and study of minerals. Examine each of the eleven observation stations containing examples of
minerals exemplifying the key physical properties of minerals. Please leave the observation stations were
they are; student should move from station to station with their lab worksheet. Learn how to recognize the
key physical properties in mineral samples. Several important minerals will be described.
Station 1: Crystal Form. Minerals form crystal faces when given room to grow without space restrictions.
The large feldspar crystals we saw in the local granite on our walking field trip the first week of lab are a
good example. The crystal forms displayed in this station are cubes, prismatic, blocky, and equant.
 Cubic: Pyrite and halite are examples of cubic crystal forms. Look for the 90 angles between all of
the surfaces in these minerals. Note that galena, which you see elsewhere in this lab, also has a cubic
crystal form. In all these examples, crystal form can be the same, but other physical properties,
including luster and density can differ greatly. Halite and galena share similar atomic structures.
Even the form of their chemical formulas are similar: NaCl (halite) vs. PbS (galena).
 Prismatic: Quartz has a six-sided prismatic crystal form. The crystal faces usually form a point at
one end of the prism but not at the other end.
 Blocky: These crystals look like building blocks. The feldspars are good examples.
Geology 2 – Physical Geology
Mineral Identification

Equant: An equant crystal has all equal sides, or very similar, but it is not a cube or a rectangle, such
as this garnet crystal.
Station 2: Luster and Density. These two properties are not related, but the two minerals shown here,
fluorite and galena, illustrate their properties very well.
 Luster: Fluorite illustrates vitreous luster: it looks like glass. Galena has metallic luster: it shines
like metal. These two types of luster are the two most common and serve to discriminate between the
two main classes of minerals: metallic and nonmetallic (see tables below).
 Density: Note that the galena is much heavier than the fluorite, even though the samples are about
the same size. Thus, the density of galena is much greater than that of fluorite. The reason is that
galena contains lead, one of the heaviest elements. The chemical formula for galena is lead sulfide
(PbS). Fluorite, on the other hand, contains calcium and fluoride (CaF2), both of which are much
lighter than lead.
Station 3: Color. Except for some minerals, color is a commonly misleading characteristic in
distinguishing minerals from one another. For examples of variability in color, look at these samples of
quartz and fluorite. Both of these samples show that each of these minerals can have several different colors.
Other minerals --olivine, for example -- are almost always the same color and it is the main distinguishing
characteristic for this mineral.
Station 4: Streak. The streak of a mineral is the color of the powder left on a streak plate (the small white
square piece of unglazed porcelain tile) when the mineral is scraped across it. Many minerals have a
different color when powdered than they do in crystal form or hand samples. The color may be entirely
different, or it may be a different shade. Quite a few minerals give a powder streak that is lighter in color
than the whole crystal or hand sample. Sometimes the color, and even luster of a mineral’s streak will differ
from that of the mineral hand sample. The hematite samples show this characteristic. Streak color is a more
consistent characteristic of a mineral than the hand sample color. Streak can be useful for identifying the
metallic or submetallic minerals. Nonmetallic minerals usually give a white streak because they are very
light-colored.
 Chalcopyrite - What is the streak of chalcopyrite? Does the streak match the color of the hand
sample? The combination of streak and hand sample color are the best distinguishing characteristics
of chalcopyrite.

Hematite - What is the streak of hematite? Does the streak match the color of the hand sample? Try
the streak of another hand sample of hematite. Notice that the physical properties (i.e., luster) of the
hand samples of hematite may vary. Does the streak color change?
Station 5: Hardness. The hardness of a mineral is its ability to resist scratching. The Mohs Hardness Scale
ranks the order of hardness of minerals and some common objects. For example, your fingernail can scratch
the minerals talc and gypsum that have a harness of 2 or lower. A copper penny has the same hardness as
fluorite so it can not scratch fluorite. But the penny can scratch softer minerals such as calcite, gypsum and
talc. Look for the Mohs Hardness Scale chart at this station. Compare the hardness of these three minerals:
corundum, quartz, and gypsum. Corundum is the hardest of the common minerals (9 on the Mohs Hardness
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Geology 2 – Physical Geology
Mineral Identification
Scale). Diamond, one of the only naturally occurring substances that is harder than corundum, is a 10 on the
Mohs scale.
 Does corundum scratch quartz?

The hardness of quartz is 7. Does glass or the copper penny scratch quartz?

Gypsum is very soft with a hardness of 2. Is the gypsum harder or softer than your fingernail?
Station 6: Cleavage. The ability of a mineral to break along preferred planes is known as cleavage. Types
of cleavage include sheet, cubic, blocky, prismatic, and rhombohedral. The key here is to establish the
number of directions of cleavage and to estimate the quality of the cleavage. The quality of mineral’s
cleavage is “perfect” if is almost always breaks in a preferred direction. Minerals that have “good” cleavage
sometimes will break in a particular direction, and other times they may not. It is sometimes difficult to
distinguish between crystal faces and cleavage faces. Generally, cleavage faces can be repetitive and parallel,
and can appear in a “step like” pattern, whereas there is often only one crystal face. Cleavage is always
parallel to crystal faces.
 Muscovite and biotite are members of the mica group of minerals; they have one direction of
cleavage, or “perfect” cleavage. Can you see the outline of the crystal faces on any of the mica
samples? What is the distinguishing characteristic between
muscovite and biotite?

Hornblende, one of the amphibole minerals, contains two directions
of cleavage at 60 and at 120 degrees from each other.

Calcite shows three directions of rhombohedral cleavage.
Station 7: Fracture. Fracture is the way a mineral breaks if it is does not break along a cleavage plane.
Like cleavage, fracture is variable and descriptive. When quartz breaks, it breaks along conchoidal fractures
– a curved break that looks like a break in a thick piece of glass. Can you identify the conchoidal fracture on
any of the obsidian samples? The quartz sample shows many overlapping conchoidal fractures.
Station 8: Other Properties - Distinctive Feels. Distinctive feel is the distinguishing characteristic for
graphite and serpentine.
 Graphite, like many other minerals, is always metallic gray. What does graphite feel like?

Serpentine comes in many colors, usually encompassing all of the greens between white and black.
Cleavage or crystal forms are rarely observable. It represents metamorphosed ultramafic (low silica
and potassium, and high magnesium and iron content) rock from the mantle altered in subduction
zones. It is often found in fault zones. Serpentine is the mineral that makes the rock Serpentinite, the
California State rock. What does serpentine feel like?
 Talc has a soapy, slippery feel. It is the source mineral of talcum powder.
Station 9: Other Properties - HCl Reaction. Calcite reacts (fizzes) when dilute HCl is applied. Over a
paper towel, drop a few drops of the HCl on the calcite and observe what happens. Don’t get it in your eyes!
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Geology 2 – Physical Geology
Mineral Identification
How do the various examples of calcite differ from one another? Can you see the rhombohedral cleavage in
all of calcite hand samples?
Station 10: Other Properties - Striations and exsolution lamellae. Striations are very straight parallel
lines visible on some of the cleavage faces of certain minerals.
 The presence of striations are an important diagnistic test to
distinguish plagioclase feldspar from potassium feldspar (Kspar). Can you find striations on the plagioclase crystal?
What are the other physical characteristics of plagioclase? Be
sure to find the striations on the pinkish sample plagioclase
feldspar. The striations are a defining property that
distinguishes plagioclase from potassium feldspar, which is
commonly pink.

Calcite sometimes contains striations that bisect the acute angle of the rhombohedral cleavage. Can
you find the striations on this sample?

Quartz can also display striations on its crystal faces. Can you see it on this quartz sample?

The little squiggly lines in the potassium feldspar (K-spar) are called exsolution lamellae. Exsolution
lamellae occurs when two minerals exsolve from a mixture and form layers called lamellae. They are
the distinguishing characteristic of this mineral. Potassium Feldspar (K-spar) is the same mineral we
saw in the local granite on our walking field trip. Draw a picture of the exsolution lamellae.
Station 11: Magnetic. Magnetite, as the name implies, is magnetic. It is the distinguishing characteristic of
this mineral. What are the other characteristics of magnetite?
Part II. Geology 2 – List of Minerals and their Distinctive Physical Properties
The following list shows the 18 minerals considered important for the purposes of Geology 2. You
will need to be able to identify each of these minerals. The minerals are listed in the form of a key designed
to use the physical properties to determine the identity of the minerals. Metallic and non-metallic minerals
are arranged by their hardness and streak or cleavage.
Each mineral has one to three “distinctive properties” that are the best physical properties to use to
identify that particular mineral. These distinctive properties are shown in bold on the mineral list. In this
part of the lab, you will see a hand sample of each mineral along with an explanation of its distinctive
physical properties as observable in the hand sample.
Walk around the room and carefully examine each of the minerals in the numbered boxes. Read their
corresponding description on the mineral list. Please be sure to return the mineral samples back into the
correct box.
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Geology 2 – Physical Geology
Mineral Identification
Geology 2 – List of Minerals and their Distinctive Physical Properties
1. Pyrite has a distinctive gold color and most often forms crystals in little cubes. The little cube crystals
often have striations on them. Use the hand lens to examine the cubic crystal forms. Pyrite is found mostly
in metamorphic rocks and in ore deposits. Name the precious metal that pyrite most resembles.
2. Magnetite is magnetic, by far its most diagnostic property. It is also submetallic and gray. What element
do you think is a principle component of magnetite?
3. Hematite always has a reddish brown streak. It can occur in a dull reddish earthy color, or as a very
metallic gray mineral, but its streak is always reddish brown. How would you tell hematite from magnetite?
4. Chalcopyrite has a distinctive gold tinsel color. It occurs in ore settings. How would you distinguish
chalcopyrite from pyrite?
5. Galena is dense, gray and very metallic. Galena is our major ore mineral for Pb (lead). Have you ever
lifted any material that is more dense than galena? If yes, what was it?
6. Graphite is soft (Mohs hardness of 1) and has a greasy feel. This mineral is used for pencil lead. It is
composed entirely of carbon, however, just like diamonds! How does the density of graphite compare to the
density of galena?
7. Quartz is translucent to transparent and produces conchoidal fractures. It is one of the most common
minerals occurring in all of the three major rock types. Because it is very hard and is resistant to weathering,
it is also a common component of beach sand and other clastic sediments. Name a place that you have seen
quartz before.
8. Garnet most often occurs as small, sub-vitreous, equant crystals. It is usually a dark color, often red, but
also greens and yellows. Garnet is very common in metamorphic rocks.
9. Plagioclase Feldspar is blocky and often contains striations, but not exsolution lamellae. Plagioclase is
common in granitic rocks. What is the best way to tell plagioclase from quartz?
10. Potassium Feldspar (K-spar) is blocky and often has exsolution lamellae, but never striations.
Potassium feldspar (K-spar) is common in granite. What is the best way to tell K-spar from plagioclase?
11. Olivine is always a distinctive shade of vitreous green and is the distinguishing mineral for basaltic rock.
It also is a very abundant mineral in the mantle. Olivine is made of Mg, Fe, and Si. How would you tell
olivine from garnet?
12. Amphibole is prismatic crystal form, black, and vitreous. It is often the dark mineral in igneous and
metamorphic rocks. Amphibole is actually a family of minerals. The most common amphibole that we will
see is hornblende.
13. Serpentine has a soapy or greasy feel and is some shade of green between black and white. Add water to
rock from the mantle and you get serpentine. Serpentinite is California’s State rock. How would you tell
serpentine from graphite?
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Geology 2 – Physical Geology
Mineral Identification
14. Fluorite is vitreous and colorful. It looks like colored glass, but is softer than quartz and does not react
with HCl, like Calcite. Fluorite forms nice crystals. Besides hardness, how would you tell fluorite from
quartz and calcite?
15. Calcite will always react with HCl by fizzing; also called effervescing. Calcite is calcium carbonate
(CaCO3), the most common carbonate. Calcite is the main constituent in a rock called limestone, which most
commonly forms in warm shallow seas. Limestone metamorphoses to form marble. How is calcite
distinguished from quartz?
16. Biotite is platy and dark. It is in the mica family. Biotite is also a common dark mineral in igneous
rocks. How can you tell biotite from amphibole?
17. Muscovite is platy and light. It is also in the mica family. How might you distinguish muscovite from
calcite?
18. Gypsum is usually white and can be scratched by your fingernail. It is the only common mineral (in this
class) that can be scratched by your fingernail. How might you tell gypsum from muscovite?
Minerals common to the three major rock groups
Igneous
Sedimentary
Olivine
Calcite
Amphibole (hornblende)
Gypsum
Biotite
Quartz
Plagioclase Feldspar
Plagioclase Feldspar
Potassium Feldspar (Kspar) Potassium Feldspar (Kspar)
Quartz
Metamorphic
Garnet
Biotite
Muscovite
Plagioclase Feldspar
Potassium Feldspar (Kspar)
Quartz
Serpentine
Ore minerals
Galena
Magnetite
Chalcopyrite
Hematite
Graphite
Part III Identification of Mystery Minerals. Check out a set of mystery minerals from the instructor.
You will have to return the complete set at the end of the lab. There are not enough sets for everybody, so
you may have to share. Use the worksheets provided on the following pages to record the physical properties
of each mystery mineral. Then, use the mineral list to key out or identify the names of the minerals. You
will need to know the names and physical properties of all the minerals in the key. You will be asked to
identify them on the mineral test. In test situations, more weight will be given to knowing the physical
property than remembering the mineral name.
Remember, not every mineral will have every physical characteristic. Focus on the “distinctive properties”
shown in bold on the table included here. Remember that you learned in Parts I and II of the lab that a
physical property of a particular mineral can vary from sample to sample. In test situations, you must
identify a physical property that is present on the specific sample given in the test.
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Geology 2 – Physical Geology
Mineral Identification
Metallic Minerals for Geology 2
Mineral
Hardness
>5.5; scratches glass, steel
Pyrite
>5.5; scratches glass, steel
Magnetite
>5.5; scratches glass, steel
Hematite
chalcopyrite >3.5, <5.5; scratched by steel,
but not by penny
>2.5, <3.5; scratched by
Galena
penny, but not fingernail
<2.5, scratched by fingernail
Graphite
Nonmetallic Minerals for Geology 2
Mineral
Hardness
Quartz
>5.5; scratches glass
Garnet
>5.5; scratches glass
Plagioclase
Feldspar
Potassium
Feldspar
Olivine
Amphibole
(Hornblende)
>5.5; scratches glass
Serpentine
Fluorite
Calcite
Biotite
Muscovite
Gypsum
>5.5; scratches glass
>5.5; scratches glass
<5.5, >3.5; scratched
by steel, but not by
penny
<5.5, >3.5; scratched
by steel, but not by
penny
<5.5, >3.5; scratched
by steel, but not by
penny
<3.5, >2.5; scratched
by penny, but not
fingernail
<3.5, >2.5; scratched
by penny, but not
fingernail
<3.5, >2.5; scratched
by penny, but not
fingernail
<2.5, scratched by
fingernail
Distinctive properties in bold
Streak
Other Properties
dark gray
gold color, cubic crystals
dark gray
gray color, magnetic
red-brown various colors,
dark gray
golden yellow color,
no cleavage
dark gray
high density,
cubic cleavage
dark gray
greasy feel
Distinctive properties in bold
Other Properties
Distinctives in bold
none, conchoidal six-sided prisms occur, translucent
fracture
to transparent, many colors, vitreous
luster
none
small, equant crystals; red, brown,
green, or pink
two directions 90 blocky crystals; striations on some
cleavage planes; white to dark
two directions 90 blocky crystals; exsolution
lamellae, white to pink
none
Always green, equant crystals
prismatic crystals
two at 60 and
120
Cleavage
none
variable hardness;
white to green to black, greasy
Four directions
cubic crystals; many colors
3 directions of
rhombohedral
cleavage
one direction
vitreous; effervesces in HCl
one direction
light color, may be softer.
one direction
translucent white
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dark color
Geology 2 – Physical Geology
Mineral Identification
Mineral Identification Worksheet
Mineral A
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Exsolution Lamellae? Y/N
Distinctive Physical Properties:
Mineral B
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Distinctive Physical Properties:
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Exsolution Lamellae? Y/N
Geology 2 – Physical Geology
Mineral Identification
Mineral C
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Exsolution Lamellae? Y/N
Distinctive Physical Properties:
Mineral D
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Distinctive Physical Properties:
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Exsolution Lamellae? Y/N
Geology 2 – Physical Geology
Mineral Identification
Mineral E
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Exsolution Lamellae? Y/N
Distinctive Physical Properties:
Mineral F
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Distinctive Physical Properties:
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Exsolution Lamellae? Y/N
Geology 2 – Physical Geology
Mineral Identification
Mineral G
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Exsolution Lamellae? Y/N
Distinctive Physical Properties:
Mineral H
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Distinctive Physical Properties:
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Exsolution Lamellae? Y/N
Geology 2 – Physical Geology
Mineral Identification
Mineral I
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Exsolution Lamellae? Y/N
Distinctive Physical Properties:
Mineral J
Name
Luster:
metallic
Hardness:
softer-than-fingernail
between-penny-and-glass
Fracture:
Conchoidal
Crystal form: cubic
vitreous
“distinctive feel” ______________________
between-fingernail-and-penny
harder-than-glass
Cleavage with number of directions____
prismatic
Streak (metallic luster only): gray
blocky
equant (equal sided)
reddish brown
none
Density: heavy light;
Other: HCl reaction? Y/N
Striations? Y/N
Exsolution Lamellae? Y/N
Distinctive Physical Properties:
Congratulations on completing the two-week Minerals identification lab! You will have opportunities to
review these minerals again before the mineral test. You will also see and hear about many of these
minerals in the up-coming Rock Identification lab.
Be aware of minerals in your daily life and in the news. Minerals are critical building blocks of our earth
and essential to our lives.
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Geology 2 – Physical Geology
Mineral Identification
MPC/Geology 2/Labs/Mineral Identification/Mineral Identification Labs 3 and 4.doc/LTS
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