Geology 101 (20 Points)
Your First & Last Name:
Names of the people in your group:
Geology Lab: The Properties of Minerals
This lab is designed to introduce you to most of the minerals that you will later see in rocks.
A mineral is a naturally-occurring, solid, inorganic compound with an orderly crystal structure and a
specific chemical composition that varies only within specific limits. Rocks are usually made of several
different minerals. For example, the rock "granite" is typically composed of 3 to 5 different minerals.
Part 1: The Physical Properties of Minerals
There are several physical properties which are useful in distinguishing minerals. The first part of this
lab introduces you to some of the properties used for mineral identification. For each question below, go to the
corresponding station, examine the specimens and answer the questions.
Station 1: “Luster” or “How does it shine”?
Luster describes the appearance of a mineral when it reflects light. The Luster of a mineral may be
either metallic or nonmetallic:
A mineral with a metallic luster will shine (= reflects light) like polished metal and be golden, copper, silver,
or gray in color
Minerals with a non-metallic lusters will not look like polished metal: They may have:
Glassy luster = reflects light in a manner similar to glass
Dull luster = has no shine
Pearly luster = reflects light like a pearl (with a hint of iridescence)
At station 1A are samples that show examples of the different types of lusters that minerals may display. 1st
examine the samples of different types of luster, and then examine the hand samples at station 1B and the listed
minerals located in the display cabinet.
Determine the luster of each of the 8 minerals listed below and write the mineral’s name under the
appropriate category below:
Hand samples = “Quartz,” “Calcite,” “Biotite,” “Talc,” and “Graphite”
Minerals in the display cabinets: at the side of the class room by the screen = “Galena,” “Pyrite,”&
“Garnet,”
Minerals with Metallic Luster:
Minerals with Non Nonmetallic Luster:
1
Station 2: Hardness = How strong are minerals?
Hardness is defined as a mineral's resistance to being scratched or broken. Geologists use a scale called
“Mohs' hardness scale” to quantify a mineral’s hardness (softest = 1, hardest = 10). For example the hardness
of Graphite = 1 and Diamonds =10.
Most of the time we do not know the exact hardness of a mineral, but we can determine the approximate
hardness of a mineral by comparing it with common objects that have a known hardness.
Using the scale below, determine the approximate hardness of the samples at this station:
Moh’s hardness number
Object
2 - 2.5
Fingernail
3.5
Copper penny
5.5
Glass plate
 List the mineral name & approximate hardness below (Ex., you may list the hardness as “< 2.0,” “>
5.5,” or as “between 5.5 and 3.5,” etc.)
2-1
2-2
2-3
2-4
2-5
2-6
2-7
Station 3: Cleavage- What happens when you break a mineral?
Cleavage is the tendency of minerals to break (or cleave) along smooth, parallel planes. Minerals that
break cleanly along a smooth surface have good cleavage. Minerals which break along a ragged line producing
a rough surface are said to have poor cleavage.
Check out the examples of mineral cleavage in the display cabinet at the back of the room:
Muscovite has excellent cleavage in one direction (note that each broken piece has one smooth side).
Hornblende has moderately-good cleavage (still break along a plane, but it’s not so smooth) in 2 direction.
Halite (common name = rock salt) has good cleavage in 3 directions (all 3 sides breaks smoothly).
Fracture: Not every mineral has a cleavage plane; some simply fracture in random patterns- this is called
fracture.
For each sample provided determine whether they display good cleavage or fracture. List the mineral
name and whether it shows “Cleavage” or “Fracture:”
1)
4)
2)
5)
3)
6)
2
Station 4- The Acid Test:
Acid reaction. Mineral that contain calcium carbonate (CaCO3) will react with diluted hydrochloric
acid (HCl), to form bubbles of carbon dioxide (CO2) gas. Use the bottle of (very weak) hydrochloric acid
provided. Put ONE drop on each sample and list the reaction of each sample in the space provided below:
Minerals that React to HCl
Minerals that do not react to HCl
Station 5: Color
Color is one of the most obvious properties of a mineral, and sometimes the color of a mineral is
distinctive, but sometime color is not distinctive as the same minerals may occur in many different colors.
5A: Quartz. Examine the hand samples provided and the quarts samples in the display cabinets at the back of
the room (don’t miss the “gem varieties of quartz”). How many different colors of quartz are shown here?
 What colors are most commonly found in quartz? (Hint: check your handout.) Is color useful in helping
to identify quartz? Explain your answer.
 Identify 2 properties other than color that the quartz hand samples share that could help you
recognize quartz (hint: check your handout again if you’re having trouble).
5B. Salmon/Pink colored mineral. What is the name of the mineral(s) in these samples (Hint: check your
mineral handout- there is only one mineral that is listed as sometimes being salmon colored).
5C. Olive-green mineral. What is the green mineral? (Hint: it’s not quartz, so check your handout). Is color a
definitive property of this mineral? Justify your answer.
5D. Fluorescent Rock Display (Front Cabinet)
Under white light these minerals are mostly dull white, gray, or black (with some purple). What colors do these
minerals glow under ultraviolet light (= black light).
3
Part II: Identification of Unknown Minerals
Identify the self quiz (= SQ) mineral specimens in Room 110, using the mineral ID handout probided .
Note: most rock samples will not have minerals as large as the onesprovided here , so take notice of diagnostic
characteristics that do not depend on size. Check your answers on this section with me before turning in your lab.
mineral #
Luster
(metallic or
non- metallic)
Hardness Cleavage?
(Y or N)
List at least 1 other property
that helped you identify this
mineral
Mineral Name
SQ-1
SQ-2
SQ-3
SQ-4
SQ-5
SQ-6
SQ-7
(hint = black mineral in SQ-9)
SQ-8
Only the
red-brown
mineral
Mineral X-1
Mineral X-2
4