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Name ______dATE ______cLASS ___
mINERAL lAB
S6E5.b: Investigate the composition of rocks in terms of minerals.
Problem: What is the relative hardness of five common minerals?
Hypothesis: Which of the minerals do you think will be the hardest?
HARDNESS Experiment:
Materials: streak plate, glass plate, penny, magnet
Minerals: Fluorite, Galena, Sulfur, Graphite, Hematite, Magnetite
Directions: Rub a mineral sample across your fingernail, a penny, and a glass plate. Did the mineral leave a scratch mark on your fingernail, the penny, or the plate?
Observation:
1. Write your answers in the table below.
Did the mineral scratch the...fingernail? / penny? / glass? / Hardness
Fluorite
Galena
Sulfur
Graphite
Hematite
Magnetite
Use the key below to determine the hardness of each mineral, and complete the table above.
If the mineral sample could be scratched by ... / Hardnessyour fingernail / 2.5
the penny but not your fingernail / 2.5-3
the glass but not the penny or your fingernail / 3-5.5
Nothing (didn’t leave a streak on the glass) / 5.5
STREAK and COLOR Experiment
1. Examine the mineral sample. Describe the color(s) of the mineral in the table below.
2. Is the mineral shiny? Write whether the sample has metallic (M) or nonmetallic (NM) luster in the table below.
3. Rub the mineral across the streak plate. Describe the color(s) of the streak in the table below. (No color -> leave blank)
4. Are the edges of the mineral rough and jagged or smooth and
flat? Write whether the mineral cleaves (C) or fractures (F) in
the table below. (Look at your notes if you need to.)
Mineral PropertiesMineral / Color(s) / Luster / Streak / Cleavage
Fluorite
Galena
Sulfur
Graphite
Hematite
Magnetite
Conclusion:
1. Which of these minerals are the hardest?
Explain how you know.
2. Which of these minerals is the softest?
Explain how you know.
3. What scale is used to determine hardness?
4. All the minerals you tested have a property that allowed you to
easily distinguish it from another mineral? Name two of those
minerals and identify the distinguishing property.
BONUS: Can you identify the mystery mineral? Finish your lab then get the mineral specimen from your teacher.
Mineral Identification Chart
Mineral / Hardness / Cleavage/Fracture / StreakHematite / 5.5 - 6.5 / Fracture / Black
Pyrite / 6 - 6.5 / Cleavage / Green-black
Galena / 2.5+ / Cleavage / Gray
Magnetite / 5.5 -6.5 / Fracture / Black
Graphite / 1 / Fracture / Black/Grey
ANSWER KEY
Observation:
1. Write your answers in the table below.
Did the _____ scratch the mineral?.fingernail? / penny? / glass? / Hardness
Magnetite / No / Yes / No / 3-5.5
Galena / No / No / No / 2.5 - 3
Graphite / Yes / No / No / <2.5
Pyrite / No / No / Yes / >5.5
Hematite / No / No
Use the key below to determine the hardness of each mineral, and complete the table above.
If the mineral sample... / Hardnessdid not scratch anything / 2.5
scratched your fingernail but not the penny / 2.5-3
scratched the fingernail and the penny but not the glass / 3-5.5
scratched everything / 5.5
2. Examine the mineral sample. Describe the color(s) of the mineral in the table below.
3. Is the mineral shiny? Write whether the sample has metallic (M) or nonmetallic (NM) luster in the table below.
4. Rub the mineral across the streak plate. Describe the color(s) of the streak in the table below.
5. Are the edges of the mineral rough and jagged or smooth and flat? Write whether the mineral cleaves in the table below.
Mineral PropertiesMineral / Color(s) / Luster / Streak / Cleavage
Magnetite / Gray / NM / White / Yes
Galena / Gray / M / Gray / Yes
Graphite / Gray / NM / Black/Gray / No
Pyrite / Gold/Yellow / M / Green/Black / Yes
Hematite / Red / NM / None / Yes
Conclusion:
1. Which of these minerals is the hardest?
Explain.
2. Which of these minerals is the softest?
Explain.
Graphite – did not scratch anything
3. Which minerals had similar characteristics?
(color, luster, cleavage, etc.)
Galena and Graphite – same color - gray
Pyrite and Galena – same cleavage - cubic
Galena and Pyrite – same luster - metallic
4. What scale is used to determine hardness?
Mohs Hardness Scale
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holts Science and Technology1Minerals of the Earth’s Crust