Earth Science SOL Unit 4.2 - Properties of Minerals

A geologist finds a mineral sample and wants to determine if it is a mineral according to scientific criteria. She observes that the sample is naturally occurring, inorganic, and solid, but it does not have a crystalline structure. Using reasoning, explain whether this sample can be classified as a mineral and justify your answer based on the properties of minerals.

• Yes, because it is naturally occurring, inorganic, and solid.

• No, because it does not have a crystalline structure, which is required for minerals.

• Yes, as long as it has a chemical formula.

• No, because it is not metallic.

Answer explanation

No, because it does not have a crystalline structure, which is required for minerals. While the sample is naturally occurring, inorganic, and solid, the lack of a crystalline structure disqualifies it from being classified as a mineral.

A student is given two mineral samples: one is gold and the other is pyrite (fool’s gold). Both appear to have a similar color. Using strategic thinking, explain why color alone is not a reliable property for identifying these minerals and suggest an alternative property that could be used for more accurate identification.

• Color is reliable; both are gold, so they are the same mineral.

• Color is not reliable because different minerals can have the same color; streak or density could be used instead.

• Color is not reliable because minerals change color in sunlight; luster is the only alternative.

• Color is reliable if the mineral is metallic; magnetism is the only alternative.

Answer explanation

Color alone is not a reliable property for identifying minerals like gold and pyrite, as different minerals can share similar colors. Instead, properties such as streak or density provide more accurate identification.

Imagine you are testing two unknown minerals for hardness using the Mohs Hardness Scale. Mineral A scratches Mineral B, but neither can scratch quartz (hardness 7). Using reasoning and evidence, determine the possible hardness values for Mineral A and Mineral B.

• Both minerals have a hardness greater than 7.

• Mineral A has a hardness less than 7, and Mineral B has a hardness less than Mineral A.

• Mineral A has a hardness greater than 7, and Mineral B has a hardness less than 7.

• Both minerals have a hardness of exactly 7.

Answer explanation

Mineral A scratches Mineral B, indicating A is harder. Since neither can scratch quartz (hardness 7), both must be less than 7. Thus, Mineral A is harder than B, confirming the correct choice.

Tags

NGSS.MS-PS1-2

A mineral sample is tested and found to attract a magnet, break into smooth cubes, and conduct electricity. Using strategic thinking, identify which properties these observations correspond to and explain what minerals might exhibit all three properties.

• Magnetism, cleavage, and conductivity; magnetite and graphite.

• Luster, color, and streak; quartz and mica.

• Hardness, density, and fracture; halite and diamond.

• Cleavage, luster, and color; pyrite and halite.

Answer explanation

The sample's magnetism indicates it contains magnetite, while its ability to break into smooth cubes suggests cleavage, and conductivity points to graphite. Thus, the properties correspond to magnetism, cleavage, and conductivity.

A scientist is comparing two minerals: one has a metallic luster and the other has a non-metallic luster. Both have the same crystal structure and density. Using reasoning, explain how luster can help distinguish between the two minerals and why other properties should also be considered for accurate identification.

• Luster alone is enough to identify minerals because it never changes.

• Luster helps distinguish minerals by their surface reflection, but other properties like streak and hardness should also be considered for accuracy.

• Luster is not useful; only color matters.

• Luster and color are the only properties needed for identification.

Answer explanation

Luster indicates how light reflects off a mineral's surface, aiding in identification. However, relying solely on luster can be misleading; properties like streak and hardness provide additional context for accurate mineral identification.

Given the Mohs Hardness Scale, if you have a mineral sample that can scratch fluorite but cannot scratch apatite, what can you infer about its hardness?

• Its hardness is less than 4.

• Its hardness is exactly 5.

• Its hardness is between 4 and 5.

• Its hardness is greater than 5.

Answer explanation

The Mohs Hardness Scale ranks fluorite at 4 and apatite at 5. Since the mineral can scratch fluorite but not apatite, its hardness must be greater than 4 but less than 5, indicating it is between 4 and 5.

A student finds that a copper penny can scratch gypsum but not calcite. Using the Mohs Hardness Scale, reason out the possible hardness of the copper penny.

• The copper penny has a hardness of about 2.5.

• The copper penny has a hardness of about 3.5.

• The copper penny has a hardness of about 4.5.

• The copper penny has a hardness of about 1.5.

Answer explanation

A copper penny can scratch gypsum (hardness 2) but not calcite (hardness 3). This indicates the penny's hardness is between these two values, making 3.5 the most accurate choice.

Imagine you are given four unknown minerals. Mineral A can be scratched by a steel nail but not by a copper penny. Mineral B can scratch fluorite but not apatite. Mineral C cannot be scratched by any other mineral except diamond. Mineral D can be scratched by all other minerals. Match each mineral to its likely position on the Mohs Hardness Scale and justify your choices.

• A: 6, B: 5, C: 10, D: 1

• A: 3, B: 4, C: 9, D: 2

• A: 2, B: 3, C: 8, D: 5

• A: 7, B: 6, C: 5, D: 4

Answer explanation

Mineral A is scratched by a steel nail (hardness 6) but not by a penny (hardness 3), so A is 6. B scratches fluorite (hardness 4) but not apatite (hardness 5), so B is 5. C is only scratched by diamond (hardness 10), and D is scratched by all, so D is 1.

If you were to design a test to determine whether an unknown mineral is harder than quartz, what steps would you take and what evidence would you use to support your conclusion?

• Try to scratch the unknown mineral with a copper penny and see if it leaves a mark.

• Try to scratch the unknown mineral with quartz and see if it gets scratched; then try to scratch quartz with the unknown mineral.

• Try to scratch the unknown mineral with talc and see if it gets scratched.

• Try to scratch the unknown mineral with a steel nail and see if it gets scratched.

Answer explanation

To determine if the unknown mineral is harder than quartz, scratch it with quartz. If it scratches the unknown mineral, then quartz is harder. If the unknown mineral scratches quartz, it is harder. This direct comparison provides clear evidence.

Tags

NGSS.MS-PS1-2