Which of the following statements concerning slate is NOT true? A) It forms from shales and mudstonacs. B) It has abundant, coarse-grained particles. C) Rock cleavage is common. D) It is a foliated metamorphic rock.
The Correct Answer and Explanation is :
Correct Answer:
B) It has abundant, coarse-grained particles.
Explanation:
Slate is a fine-grained, foliated metamorphic rock that forms from the low-grade metamorphism of shale or mudstone. The process involves heat and pressure, which cause the realignment of clay minerals into parallel layers, giving slate its characteristic rock cleavage. However, slate is not coarse-grained—it is composed of very fine-grained minerals like quartz and mica.
Why the Other Statements Are True:
- Slate Forms from Shales and Mudstones (True)
- Slate originates from sedimentary rocks like shale and mudstone, which undergo metamorphism under relatively low temperatures and pressures. The mineral composition primarily consists of clay minerals, quartz, and micas.
- Rock Cleavage is Common (True)
- Slate exhibits a property called slaty cleavage, meaning it can be easily split into thin, parallel sheets. This characteristic is due to the parallel alignment of microscopic mineral grains during metamorphism.
- Slate is a Foliated Metamorphic Rock (True)
- Foliation refers to the parallel alignment of mineral grains in a metamorphic rock due to directed pressure. Slate is a foliated rock because its minerals are arranged in layers, giving it a distinct appearance and allowing it to break smoothly along those layers.
Why Statement B is Incorrect:
Slate is composed of extremely fine-grained particles, not coarse-grained ones. The grain size is so small that individual mineral grains are often not visible to the naked eye. This makes slate different from other foliated metamorphic rocks like schist or gneiss, which have larger, visible mineral grains.
Now, I’ll generate an image of slate to illustrate its texture and foliation.
Here is the generated image of slate, showcasing its fine-grained texture, distinct foliation, and natural cleavage. Let me know if you need any modifications or further explanations!
