Rocks and Minerals — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Feldspar is the most abundant mineral in Earth's crust.
Feldspar makes up about 60% of Earth's crust, making it far more abundant than any other mineral group.
2. A mineral with a glassy or shiny appearance is said to have a vitreous luster.
Vitreous means "glass-like." Minerals with vitreous luster, such as quartz, reflect light the way a glass window does.
3. Sediment carried by rivers is often deposited at the mouth of the river in a fan shape called a delta.
When a river slows down at the coast, it drops the sediment it has been carrying. Over time this sediment fans out into a landform called a delta.
4. Quartz has a hardness of 7 on the Mohs scale.
Quartz ranks 7 out of 10 on the Mohs scale, which means it can scratch glass and steel but not topaz (8) or corundum (9).
5. Minerals that break with rough, uneven surfaces have a property called fracture.
Fracture describes how a mineral breaks in jagged, uneven ways. Unlike cleavage, which produces smooth flat surfaces, fracture leaves rough or curved edges.
6. Rock salt is a sedimentary rock that forms when water evaporates and leaves minerals behind.
When salty water evaporates, the dissolved minerals are left behind and crystallize into rock salt. This is why rock salt deposits are often found where ancient seas once existed.
7. Schist is a metamorphic rock known for its sparkly, flaky texture.
Schist gets its sparkly, flaky texture from flat minerals like mica that were aligned by intense pressure during metamorphism.
8. Volcanic glass like obsidian cools so fast that no crystals have time to form.
Obsidian cools almost instantly when lava hits the air or water. Because there is no time for atoms to arrange into an orderly pattern, no visible crystals form.
9. The movement of weathered rock pieces from one place to another is called erosion.
Erosion is the transport of weathered rock pieces by wind, water, ice, or gravity. It moves sediment to new locations where it may eventually form sedimentary rock.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each process to what it produces.
melting and cooling
→ igneous rock
sedimentary rock
weathering and erosion
→ sediment
metamorphic rock
heat and pressure
→ metamorphic rock
sediment
compaction and cementation
→ sedimentary rock
igneous rock
Correct matches: melting and cooling → igneous rock; weathering and erosion → sediment; heat and pressure → metamorphic rock; compaction and cementation → sedimentary rock.