Rocks - Practice Test 3

Attempt the quiz above first, then review every question with its correct answer and a short explanation below.

1. Q1.Clay changes into which metamorphic rock?

   • A.Slate✓ Correct Answer
   • B.Marble
   • C.Quartzite
   • D.Gneiss

   Explanation: Clay/Shale metamorphoses into Slate.

2. Q2.Gabbro is a:

   • A.Coarse-grained Intrusive Igneous rock✓ Correct Answer
   • B.Fine-grained Extrusive Igneous rock
   • C.Sedimentary rock
   • D.Metamorphic rock

   Explanation: Gabbro is the intrusive equivalent of basalt (coarse-grained).

3. Q3.Which rock forms from the accumulation of shell fragments?

   • A.Coquina (Limestone)✓ Correct Answer
   • B.Sandstone
   • C.Basalt
   • D.Granite

   Explanation: Coquina is a type of limestone made of broken shells.

4. Q4.Weathering and erosion are the first steps in the formation of:

   • A.Sedimentary rocks✓ Correct Answer
   • B.Igneous rocks
   • C.Metamorphic rocks
   • D.Magma

   Explanation: These processes break down rocks into sediments.

5. Q5.The most common group of rock-forming minerals are:

   • A.Silicates✓ Correct Answer
   • B.Carbonates
   • C.Oxides
   • D.Sulfates

   Explanation: Silicates account for over 90% of Earth's crust.

6. Q6.Rock salt (Halite) is an example of:

   • A.Chemical Sedimentary Rock✓ Correct Answer
   • B.Organic Sedimentary Rock
   • C.Igneous Rock
   • D.Metamorphic Rock

   Explanation: It forms from the evaporation of saline water (evaporite).

7. Q7.Which of these rocks is non-foliated metamorphic rock?

   • A.Marble✓ Correct Answer
   • B.Gneiss
   • C.Schist
   • D.Slate

   Explanation: Marble (and Quartzite) does not show foliation (layers).

8. Q8.Breccia is characterized by:

   • A.Angular rock fragments✓ Correct Answer
   • B.Rounded pebbles
   • C.Fine sand
   • D.Volcanic ash

   Explanation: Breccia consists of angular fragments, unlike Conglomerate (rounded).

9. Q9.Which igneous rock is light in color and density (Felsic)?

   • A.Granite✓ Correct Answer
   • B.Basalt
   • C.Gabbro
   • D.Peridotite

   Explanation: Granite is felsic (rich in silica/aluminum), making it lighter.

10. Q10.Which igneous rock is dark and dense (Mafic)?

    • A.Basalt✓ Correct Answer
    • B.Granite
    • C.Rhyolite
    • D.Pumice

    Explanation: Basalt is mafic (rich in magnesium/iron), making it darker and denser.

11. Q11.A rock that has been changed by heat and pressure is:

    • A.Metamorphic✓ Correct Answer
    • B.Igneous
    • C.Sedimentary
    • D.Magma

    Explanation: Metamorphic means 'change of form'.

12. Q12.Chalk is a form of:

    • A.Limestone✓ Correct Answer
    • B.Sandstone
    • C.Granite
    • D.Coal

    Explanation: Chalk is a soft, white, porous sedimentary limestone.

13. Q13.Which rock type is the primary source of groundwater aquifers?

    • A.Sedimentary (Sandstone/Limestone)✓ Correct Answer
    • B.Igneous
    • C.Metamorphic
    • D.Volcanic

    Explanation: Porous sedimentary rocks hold water well.

14. Q14.The parent rock of Gneiss is typically:

    • A.Granite✓ Correct Answer
    • B.Basalt
    • C.Limestone
    • D.Sandstone

    Explanation: Gneiss forms from the high-grade metamorphism of granite.

15. Q15.Which mineral gives Granite its pinkish color?

    • A.Feldspar (Orthoclase)✓ Correct Answer
    • B.Quartz
    • C.Mica
    • D.Hornblende

    Explanation: Potassium Feldspar gives granite a pink/salmon hue.

16. Q16.Which rock has large crystals embedded in a fine-grained matrix?

    • A.Porphyry✓ Correct Answer
    • B.Granite
    • C.Basalt
    • D.Obsidian

    Explanation: Porphyritic texture indicates two stages of cooling.

17. Q17.The most abundant element in Quartz is:

    • A.Silicon and Oxygen✓ Correct Answer
    • B.Iron and Oxygen
    • C.Aluminum and Oxygen
    • D.Calcium and Carbon

    Explanation: Quartz is Silicon Dioxide (SiO2).

18. Q18.Which of these is a Plutonic rock?

    • A.Granite✓ Correct Answer
    • B.Basalt
    • C.Andesite
    • D.Rhyolite

    Explanation: Granite forms deep underground (Plutonic).

19. Q19.Acidic igneous rocks have a high percentage of:

    • A.Silica✓ Correct Answer
    • B.Magnesium
    • C.Iron
    • D.Calcium

    Explanation: Acidic (Felsic) rocks have high silica content (>65%).

20. Q20.Basic igneous rocks have a high percentage of:

    • A.Iron and Magnesium✓ Correct Answer
    • B.Silica
    • C.Potassium
    • D.Sodium

    Explanation: Basic (Mafic) rocks have low silica and high Fe/Mg.