OLLI—Rock ID and Geologic Mapping
Name: _______________________
Lab 1: Mineral Identification
Introduction: In this lab activity you will become familiar with minerals and identifying
their different properties. This lab will also introduce you to the deductive process
where you will utilize the results of each property test to identify the name of the mineral
from an established key.
Materials provided:
•
•
•
•
Streak plate
Penny
Nail
Metal plate
•
•
•
•
Glass
Magnet
Dilute HCl
Hand lens
Procedure:
1. Go through and test each mineral for:
• Hardness
• Cleavage/fracture
• Color
• Density
• Streak
• Luster
2. Be sure to record all information in the data table
3. After you have tested all minerals for all 6 properties, compare your results for
each mineral to the established mineral chart in the back. Use this chart to
identify the mineral name.
Property Descriptions and Testing Procedures
Color: This is probably the most easily observed property of minerals. However, color
often varies widely and is the least reliable property for identification.
Streak: The color of the mineral when powdered. To test for streak, draw the mineral
against an unglazed porcelain tile (streak plate). Streak is more useful for identification
than color.
Cleavage or fracture: These two properties refer to the way in which a mineral breaks.
Cleavage is an orderly breakage in well-defined planes, meaning the mineral has flat
sides. Fracture is a random breakage. If a mineral breaks with rough, random surfaces, it
is said to have fracture. This can vary widely so be patient and careful.
Density: Compare the relative “heft” of a mineral by holding it in your hand and
comparing it to other minerals of about the same size. In general, metallic minerals are
heavier than non-metallic minerals. To simplify, we classify minerals as 1.) Light, 2.)
Heavy, 3.) Very heavy. Density = mass/volume
1
Hardness: A mineral’s hardness is it’s resistance to scratching. Mohs Scale of
Hardness, this scale uses common everyday objects to test hardness of each mineral
sample. Below is the resulting table.
Moh’s Hardness Scale
Rating
1
2
3
4
5
6
7
8
9
10
Type Mineral
Talc
Gypsum
Calcite
Fluorite
Apatite
Feldspar
Quartz
Topaz
Corundum
Diamond
Object used to test
Hardness
Talc
Fingernail-2.5
Penny-3.5
Nail-4.5
Glass-5.5
Steel file-6.5
Streak plate-7
Luster: Refers to the way that a mineral reflects light. The simplest distinction is
between metallic luster (shiny and gold or silver color) and nonmetallic luster (does not
look like a metal in color, although it may be shiny). Particular types of nonmetallic
luster include pearly, vitreous (glassy), resinous (has the appearance of resin), silky, and
earthy (dull).
Other properties
Here are three additional tests that you should perform on all your rocks. If you get a
positive test, record it in your “other properties” column.
•
TASTE TEST: Certain Minerals have a particular taste. Two minerals, halide and
quartz, are very similar in appearance. One simple way to tell them apart is that
halide has a salty taste whereas quartz has no taste.
•
SMELL TEST: Certain minerals give off a very distinct smell. Sulfur, for
instance, smells like rotten eggs.
•
ACID TEST: You should test your rocks to see if they will react with
hydrochloric acid. Put a single drop on each rock, one at a time. If you
immediately see a vigorous fizzing, it is calcite. Dolomite reacts only when
scratched.
•
MAGNET TEST: If one of your rocks is attracted to a magnet, it may be
magnetite. But check all the other properties too because other iron ores are also
easily magnetized.
2
Name: ____________________
#
1
2
3
4
5
6
7
8
9
Mineral Name
(fill in last)
Color
Streak
Hardness
Cleavage
or
Fracture
Density/Heft
(Light,
Medium,
Heavy)
Luster
Metallic/NonMetallic
Other
Properties/Notes
Mineral Name
Possible Colors
Streak
Hardness
Cleavage
or
Fracture
Luster
Metallic/NonMetallic
Cleavage
Density/Heft
Light,
Medium,
Heavy
Light
Azurite
Blue
Blue
3.5-4
Biotite
Brown
None
Calcite
Clear to milky,
orange, tan
Chalcopyrite
Other
Properties/notes
2.5-3
Cleaves 1 plane
Light
White
3
Cleavage
Light
Non-Metallic,
glassy, almost
translucent
Non-Metallic,
vitreous-pearly
Brassy, Yellow,
reddish
Greenish-black
3.5-4
Fractures
Heavy
Metallic
Feldspar
Gray, green
orange
Colorless
6
Light
Non-Metallic
Galena
Blue – black,
grey
Grey-black
2.5
Two planes of
cleavage that
meet at right
angles
Cleavage
Heavy
Metallic
Crystals maybe
cut, very heavy
Garnet
Red, orange,
purple, green
Colorless
7
Fracture
Medium
Non-Metallic,
vitreous
Octahedral
crystals
Graphite
Grey
Grey
1.2
Cleavage
Light
Metallic
Draws on paper
Gypsum
Pinkish-white,
white, grey,
reddish-brown
White
1.5-2 scratches
with fingernail
Cleaves
Light
Non-Metallic,
vitreous-silky
Non-Metallic
Very flexible
Reacts with acid
Mineral Name
Possible Colors
Streak
Hardness
Cleavage
(how many
planes)
or
Fracture
Cleaves at right
angles
Density/Heft
Light,
Medium,
Heavy
Luster
Metallic/NonMetallic
Other
Properties
Halite
Clear, white
None
2.5
Light
Non-Metallic
Tastes salty
Hematite
Black, grey,
reddish-brown
Reddish-brown
5.5-6.5
Fracture
Heavy
Metallic or rusty
Hornblende
Dark –green,
shiny bluishblack
Grey-black
Gray to white
5-6
Light
Non-Metallic,
vitreous
crystals are
needle shaped
Black
6
Heavy
Metallic
Magnetic
Clear, white,
light brown
Colorless, light
brown
2-2.5
Cleaves into
needlelike
fragments
Non cleavage,
but octahedral
parting
Cleaves in 1
plane
Muscovite
Light
Non-Metallic,
vitreous-pearly
Flat flexible
crystals
Pyrite
Golden-brassy,
yellow
Greenish black
6-6.5
Fracture
Medium
Metallic
Quartz
None
7
Non-Metallic,
vitreous
White
1.5-2.5
No cleavage,
but conchoidal
fracture
Fractures
Light
Sulfur
Clear, white,
purple, rose,
grey
Yellow
Light
Non-Metallic,
resinous-dull
Smells like eggs
Talc
White, green
White
1
Cleaves
Light
Non-metallic,
Greasy/pearly
Powdery-greasy
feel
Magnetite
OLLI—Rock ID and Geologic Mapping
Name: _____________________
Lab 1: Mineral identification—OPTIONAL worksheet
This is a review to keep you fresh on the material. It can be filled out after class/lab.
1. What are the 6 properties used to identify minerals
a.
b.
c.
d.
e.
f.
2. Briefly describe how you would test a mineral for each of these properties
a.
b.
c.
d.
e.
f.
3. What tool is used to determine the streak of a mineral?
Answer:___________
4. What is the name of the scale used to determine hardness?
Answer:___________
5. What is the difference between cleavage and fracture?
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
6. What are the two major categories of luster?
Answer:______________
Answer:______________
7. List types of Non-Metallic Luster