PHYSICAL GEOLOGY Minerals Chapter 3 1 Not counting elements and sub-atomic particles minerals are the basic building block for the majority of earthen materials. Minerals are the major constituent of nearly all rocks. Combinations of minerals (mineral assemblages) in rocks can give insight into the formation and possible alteration of the rocks in question. Identification of minerals is a process of interpreting the physical and other properties of the mineral. In this laboratory assignment you will become familiar with many of the properties of minerals and how to test these properties. Finally by utilizing this data and identification charts you will be able to determine the mineral species. Mineral: Naturally occurring, inorganic, homogenous, solid, element or compound with a characteristic chemical composition and definite crystalline structure. Properties Color: The color of the mineral. Color is not the best property to use to identify minerals. Many minerals occur in multiple colors, impurities in the chemical composition may alter the color. Many different minerals occur in the same colors. Luster: The way in which light is reflected off the minerals surface.  Metallic – reflects light like a polished metal (such as gold, silver, lead, bronze, and iron)  Submetallic – reflects light like a corroded metal (such as cast iron or rust)  Vitreous – reflects light like glass (might not be transparent)  Adamantine – reflects light like a diamond  Resinous – reflects light like amber  Pearly – reflects light like mother-of-pearl  Satiny – reflects light like satin or silt cloth, more reflective in one direction  Greasy/oily - reflects light like an oil coated substance  Waxy - reflects light like a candle or a crayon  Dull/earthy – reflects light like dirt or rust Streak Color: The color of the mineral when powdered. Minerals softer than a Mohs hardness of seven can be powdered by rubbing the sample on an unglazed porcelain plate. Minerals with a hardness seven or higher must be crushed. Cleavage: The tendency of some minerals to break along parallel planar surfaces (parting: pseudo cleavage). Habit: The form (shape) the mineral will grow if unimpeded.  Acicular – needle like  Bladed - like a knife blade  Equant – roughly box-like or ball like e.g. cubic, octahedral  Mammillary – rounded masses  Micaceous – thin sheets  Oolitic – small spheres (~1-3mm)  Prismatic – elongated with opposite parallel faces  Tabular – flat, plate-like Hardness: The minerals resistance to being scratched. In 1812 Friedrich Mohs created a scale using ten common rock forming mineral to compare the differing hardnesses of all minerals. Starting at the softest and proceeding to the hardest. 1. talc 2. gypsum 3. calcite 4. fluorite 5. apatite 6. feldspars 7. quartz 8. topaz 9. corundum 10. diamond. Besides Mohs’ minerals; there.

1. PHYSICAL GEOLOGY Minerals
Chapter 3 1
Not counting elements and sub-atomic particles minerals are the
basic building block for the majority of earthen materials.
Minerals
are the major constituent of nearly all rocks. Combinations of
minerals (mineral assemblages) in rocks can give insight into
the
formation and possible alteration of the rocks in question.
Identification of minerals is a process of interpreting the
physical and other properties of the mineral. In this laboratory
assignment you will become familiar with many of the
properties of
minerals and how to test these properties. Finally by utilizing
this
data and identification charts you will be able to determine the
mineral species.

2. Mineral: Naturally occurring, inorganic, homogenous,
solid, element or compound with a characteristic chemical
composition and definite crystalline structure.
Properties
Color: The color of the mineral. Color is not the best
property to use to identify minerals. Many minerals occur in
multiple
colors, impurities in the chemical composition may alter the
color.
Many different minerals occur in the same colors.
Luster: The way in which light is reflected off the minerals
surface.
– reflects light like a polished metal (such as
gold, silver, lead, bronze, and iron)
– reflects light like a corroded metal (such
as cast iron or rust)
– reflects light like glass (might not be
transparent)
– reflects light like a diamond

3. – reflects light like amber
– reflects light like mother-of-pearl
– reflects light like satin or silt cloth, more
reflective in one direction
- reflects light like an oil coated substance
axy - reflects light like a candle or a crayon
– reflects light like dirt or rust
Streak Color: The color of the mineral when powdered.
Minerals softer than a Mohs hardness of seven can be powdered
by
rubbing the sample on an unglazed porcelain plate. Minerals
with a
hardness seven or higher must be crushed.
Cleavage: The tendency of some minerals to break along
parallel planar surfaces (parting: pseudo cleavage).
Habit: The form (shape) the mineral will grow if
unimpeded.
– needle like

4. - like a knife blade
– roughly box-like or ball like e.g. cubic,
octahedral
– rounded masses
– thin sheets
– small spheres (~1-3mm)
– elongated with opposite parallel
faces
– flat, plate-like
Hardness: The minerals resistance to being scratched. In
1812 Friedrich Mohs created a scale using ten common rock
forming
mineral to compare the differing hardnesses of all minerals.
Starting
at the softest and proceeding to the hardest. 1. talc 2. gypsum 3.
calcite 4. fluorite 5. apatite 6. feldspars 7. quartz 8. topaz 9.
corundum 10. diamond. Besides Mohs’ minerals; there are
common
items we can also use to determine a minerals hardness. Your
fingernail is about 2.5, a copper penny is about 3.5, a wire nail

5. is
about 4.5, a glass plate is about 5.5, and a scratch plate is about
7
(See table 3.1). Mohs scale is not incremental. Gypsum, number
two
is not twice as hard as talc number one. Diamond, number ten is
not
ten times as harder than talc. In absolute hardness diamond is
1600
times harder than talk.
Cubic: three cleavages (six faces) all at right-
angles (90°)
Octahedral: four cleavages (eight faces)
Dodecahedral: six cleavages (twelve faces)
Rhombohedral: three cleavages (six faces) not at
90°
Prismatic: two cleavages (four faces) fifth and
sixth sides are fractured
Basal: one cleavage (two faces)

6. PHYSICAL GEOLOGY Minerals
Chapter 3 2
To identify the hardness of the mineral in question you will
attempt
to scratch the mineral with the minerals in the Mohs hardness
kit
and/or the other common items. If the mineral is scratched it is
softer than that mineral or item. If the mineral is not scratched
by
the item or it can scratch the item, it is harder than the item. If
the
mineral and the item scratch each other they have an equivalent
hardness.
Mohs hardness Absolute hardness
talc 1 1
gypsum 2 3
fingernail 2.5
calcite 3 9
copper penny 3.5

7. fluorite 4 21
wire nail 4.5
apatite 5 48
glass plate 5.5
feldspars 6 72
quarts 7 100
topaz 8 200
corundum 9 400
diamond 10 1600
Table 3.1 Mineral hardness scale. Including Mohs hardness
scale,
alternate item and absolute hardness.
Other properties:
– the mineral is attracted to a magnet.
– the mineral has a distinct taste.
– the mineral has a distinct smell.
– the mineral effervesces in dilute
acid.

8. – the mineral has a certain feel to it (such as
soapy or gritty).
– how dense the mineral is.
– the mineral seems heavy or light relative to its
size.
– fine parallel “scratches”
– “vain” looking pattern of lighter
and darker coloration
Pick samples 25 through 32.
Arrange the minerals by any criteria. What was the criterion
and
what was the order?
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Now arrange them by another criterion. What was the criterion

9. and
what was the order?
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0
1
2
3
4
5
6
7
8

10. 9
10
0 200 400 600 800 1000 1200 1400 1600
Mohs vs. Absolute hardness
Mohs Absolute
diamond
corundum
topaz
quartz
feldspars
apatite
fluorite
calcite
gypsum
talc
PHYSICAL GEOLOGY Minerals

11. Chapter 3 3
Metallic and Sub-Metallic Lusters
Streak Hardness Cleavage or
Fracture
Color Other Properties Mineral Name
Dark Gray to Black 6.0-6.5 Fracture Brass-yellow to Gold;
tarnished dark gray
Habit equant; occasionally
striated
Pyrite
6.0-6.5 Fracture Silvery dark gray;
tarnished to black
Habit octahedral; strongly
attracted magnets
Magnetite
3.5-4.0 Fracture Greenish gold;
tarnished to goldish
brown
Habit equant Chalcopyrite
3.0 Fracture Brown bronze;
Tarnishes black with
blue to purple
iridescence

12. Habit granular masses; may
be weakly attracted to
magnets
Bornite
2.5 Excellent; three
direction (cubic)
Slivery gray; tarnishes
to dark dull gray
Habit equant Galena
1.0-2.0 Perfect, one
direction (basal); too
small to see
Dark silvery gray to
black
Habit tabular; can be
scratched with fingernail,
rubs off easily on surfaces
Graphite
Brown 5.5-6.0 Fracture Silvery black to black;
tarnishes dark gray to
black
Habit equant; may be weakly
attracted to magnets
Chromite

13. Yellow-brown 5.0-5.5 Perfect, one
direction (basal); too
small to see
Yellowish brown to red-
brown
Habit acicular (radiating
needle like) often
microscopic; also non-metallic
Goethite
White to pale yellow-
brown
3.5-4.0 Perfect, six direction
(dodecahedral);
often too small to
see
Silvery yellow-brown
silvery red; tarnishes
Black
Habit equant; rotten egg
smell when scratched or
powdered; also non-metallic
Sphalerite
Red to red-brown 5.0-6.0 (1.0-5.0
nonmetallic)

14. Parting Gray to silver Slivery verity is glittery; may
be weakly attracted to
magnets; Also non-metallic
Hematite
PHYSICAL GEOLOGY Minerals
Chapter 3 4
Nonmetallic Lusters (light colored)
Hardness Cleavage or
Fracture
Color Other Properties Mineral Name
9.0 Parting and
conchoidal fracture
Red (ruby), Blue
(sapphire)
Luster vitreous; habit prismatic; streak none Corundum
8.0 Perfect, one direction
(basal)
Colorless, yellow, blue,

15. green, violet, orange
Luster vitreous; habit prismatic; streak white Topaz
7.0 Conchoidal fracture Green (forsterite), Orange
(fayalite)
Luster vitreous; granular massive; streak white
to pale green
Olivine
7.0 Conchoidal fracture Pink (rose quartz), yellow
(citrine), white (milky
quartz)
Luster vitreous; prismatic and pyramids,
amorphous; streak white
Quartz
6.0 Excellent, two
directions (prismatic)
nearly 90°
White, gray Luster vitreous; habit prismatic; streak white;
striations on cleavage plains
Plagioclase feldspar
6.0 Excellent, two
directions (prismatic)
nearly 90°
Colorless, orange, brown,
white, green, gray, pink

16. Luster vitreous; habit prismatic; streak white;
exsolution lamellae
Orthoclase feldspar
(potassium feldspar)
5.5-6.0 Conchoidal fracture White, orange, yellow,
brown, blue, gray, green,
red
Luster vitreous; amorphous masses; streak
white
Opal
5.0 Conchoidal fracture Pale green, brown, blue,
white, purple
Luster vitreous to sub-vitreous; habit prismatic;
streak white
Apatite
4.0-7.0 Excellent, two
directions (prismatic)
Blue, light gray, white,
pale green
Luster vitreous to pearly ; habit bladed; streak
white; hardness of 4-5 along the length of the
blade 6-7 across the blade
Kyanite

17. 4.0 Excellent, four
directions (octahedral)
Colorless, green, purple,
Blue, gray, yellow
Luster vitreous; habit equant; streak white;
fluoresces in ultra violet light
Fluorite
3.5-4.0 Excellent, three
directions
(rhombohedral)
White, grey, pink, light tan Luster vitreous to pearly; Habit
equant, slightly
curves faces; streak white; slight reaction to
dilute acid (HCl) more so if powdered
Dolomite
3.0-3.5 Good, two direction
(prismatic)
White to off-white with
brown, blue or black
streaks
Luster vitreous to pearly to greasy; habit
tabular; heavy
Barite
3.0 Excellent, three
directions

18. (rhombohedral)
Colorless, white, yellow,
green, brown, pink
Luster vitreous to pearly; habit equant; streak
white; reacts to dilute acid (HCl)
Calcite
2.5 Excellent, three
directions (cubic)
Colorless, white, yellow,
blue, brown, pink
Luster glassy to resinous; habit equant; steak
white; salty taste
Halite
2.0-2.5 Excellent, one
direction (basal)
Colorless to silvery white Luster vitreous to pearly; habit
micaceous;
streaks white; occurs in books of many sheets;
books look more metallic while single sheets
are colorless
Muscovite Mica
2.0 Perfect, one direction
(basal), with two poor
Colorless, many pastel

19. colors
Luster vitreous to pearly to satiny; habit
tabular (sometime forms rosettes) streak white
Gypsum
1.5-2.5 Fracture Yellow Luster resinous; streak yellow; rotten
egg
smell, stronger when scratched
sulfur
1.0 Perfect, one direction
(basal)
White to green Luster pearly, greasy, resinous; habit tabular;
streak white; very soft (scratches easily with
fingernail)
Talc
PHYSICAL GEOLOGY Minerals
Chapter 3 5
Nonmetallic Lusters (Dark Colored)
Hardness Cleavage or

20. Fracture
Color Other Properties Mineral Name
9.0 Parting and
conchoidal fracture
Red (ruby), Blue
(sapphire)
Luster vitreous; habit prismatic; streak none Corundum
7.0-7.5 Fracture Black, green, gradation
from green to pink
Luster vitreous; habit prismatic; streak white;
striations along the length
Tourmaline
7.0 Conchoidal fracture Green (forsterite), Orange
(fayalite)
Luster vitreous; granular massive; streak white
to pale green
Olivine
7.0 Conchoidal fracture Gray, brown (smoky
quartz), purple (amethyst)
Luster vitreous; greasy; prismatic and
pyramidal, amorphous; streak white
Quartz

21. 7.0 Fracture Red, brown, orange, pale
green, off-white
Luster vitreous; habit equant; streak white;
variable crystal faces 12, 24, 36
Garnet
6.0 Excellent, two
directions (prismatic)
nearly 90°
Dark gray, blue, black Luster vitreous; habit prismatic; streak
white;
striations on cleavage plains
Plagioclase feldspar
6.0 Excellent, two
directions (prismatic)
nearly 90°
Translucent, brown, gray,
green, red
Luster vitreous; habit prismatic; streak white;
exsolution lamellae
Orthoclase feldspar
(potassium feldspar)
5.5-6.0 Excellent, two
directions (prismatic)
~56° and ~124°
Black, dark green Luster vitreous, pearly, dull; habit prismatic;

22. streak white, greenish brown
Hornblende
(amphibole)
5.5-6.0 Excellent, two
directions (prismatic)
nearly 90°
Black, dark green Luster vitreous, resinous, dull; habit
columnar;
streak greenish gray
Augite
(pyroxene)
5.0 Conchoidal fracture Pale green, brown, blue,
white, purple
Luster vitreous to sub-vitreous; habit prismatic;
streak white
Apatite
4.0 Excellent, four
directions (octahedral)
Colorless, green, purple,
Blue, gray, yellow
Luster vitreous; habit equant; streak white;
fluoresces in ultra violet light
Fluorite
3.5-4.0 Perfect, six direction

23. (dodecahedral); often
too small to see
Silvery yellow-brown
silvery red; tarnishes Black
Luster resinous, greasy; Habit equant; streak
yellow; rotten egg smell when scratched or
powdered; also metallic luster
Sphalerite
3.5-4.0 Perfect, one direction
(basal), poor one
Azure blue, blue, light
blue, dark blue,
Luster vitreous, adamantine; habit tabular;
streak pale blue
Azurite
3.5-4.0 Perfect, one direction
(basal), fair one
Light green, green, dark
green
Luster vitreous, satiny; habit columnar; streak
light green; may form in mammillary masses
Malachite
2.5-3.0 Perfect, one direction
(basal)

24. Brown, green brown,
black
Luster vitreous, resinous, pearly; habit
micaceous; streak gray; transparent brown as
single sheets
Biotite
2.0-3.0 excellent, one
direction (basal)
Light green, dark green,
yellow, white
Luster vitreous, dull; habit tabular; streak white Chlorite
1.5-5.0 Parting Brick red to reddish grey Luster dull-earthy;
may be weakly attracted to
magnets; sometimes oolitic (little spheres);
Also metallic luster
Hematite
1.0-5.5 Perfect, one direction
(basal); too small to
see
Yellowish brown to red-
brown
Luster dull-earthy; Habit acicular (radiating
needle like) often microscopic; also metallic
Goethite

25. 1.0-3.0 Fracture Gray Luster Dull Earthy; habit spherical
grains;
streak white ,pale brown, gray; small pea sized
orbs
Bauxite
1.0 Perfect, one direction
(basal)
White to green Luster pearly, greasy, resinous; habit tabular;
streak white; very soft (scratches easily with
fingernail)
Talc
PHYSICAL GEOLOGY Minerals
Chapter 3 6
Sample Hardness Cleavage Luster Color Other Properties
Mineral Name
Streak Color
1

26. 2
3
4
5
6
7
8
9
10
11
12
13

27. 14
15
16
PHYSICAL GEOLOGY Minerals
Chapter 3 7
Sample Hardness Cleavage Luster Color Other Properties
Mineral Name
Streak Color
17
18
19
20

28. 21
22
23
24
25
26
27
28
29
30
31
32