Question

Describe gneiss, schist, phyllite, and slate in terms of texture and grain size.

a. All four rocks are nonfoliated, with slate having the smallest mineral grains, phyllite having the second smallest mineral grains, schist having the second largest mineral grains, and gneiss having the largest mineral grains.
b. All four rocks are foliated, with slate having the largest mineral grains, phyllite having the second largest mineral grains, schist having the second smallest mineral grains, and gneiss having the smallest mineral grains.
c. All four rocks are nonfoliated, with slate having the largest mineral grains, phyllite having the second largest mineral grains, schist having the second smallest mineral grains, and gneiss having the smallest mineral grains.
d. All four rocks are foliated, with slate having the smallest mineral grains, phyllite having the second smallest mineral grains, schist having the second largest mineral grains, and gneiss having the largest mineral grains.
e/ All four rocks are porphyroblastic, with slate having the smallest mineral grains in its matrix, phyllite having the second smallest mineral grains in its matrix, schist having the second largest mineral grains in its matrix, and gneiss having the largest mineral grains in its matrix.

Answer 1

The four metamorphic rocks in question—gneiss, schist, phyllite, and slate—are all foliated, with grain sizes increasing from slate (smallest) to gneiss (largest).

Step-by-step explanation:

When describing the texture and grain size of gneiss, schist, phyllite, and slate, all of which are types of metamorphic rocks, it's important to recognize that they are foliated and differ in grain size.

The correct description is that all four rocks are foliated, with slate having the smallest mineral grains, phyllite having slightly larger mineral grains than slate, schist having larger mineral grains and more conspicuous foliation compared to phyllite, and gneiss having the largest mineral grains along with distinctive banding or gneissic foliation, often with segregation of light and dark minerals.

Thus, the accurate statement is:
d. All four rocks are foliated, with slate having the smallest mineral grains, phyllite having the second smallest mineral grains, schist having the second largest mineral grains, and gneiss having the largest mineral grains.