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An introduction to geology
An introduction to geology

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1.4 Identifying rock textures

Take a look at a hand specimen and a thin section of each of these rocks:

(open the links in a new window so you can come back to this page more easily)

When you've taken a good look at the rocks, complete the quiz below.

Activity _unit1.5.1 Activity 1.2 Rock specimen quiz

Timing: Allow about 10 minutes

You may take as many attempts as you wish to answer each question, and you can skip questions and come back to them later if you wish.

1. Select all the correct observations of each textural feature of gneiss:

a. 

Interlocking crystals


b. 

Rounded grains


c. 

Randomly oriented crystals/grains


d. 

Crystals/grains showing banding or alignment in one preferred direction


The correct answers are a and d.

2. Select all the correct observations of each textural feature of conglomerate:

a. 

Interlocking crystals


b. 

Rounded grains


c. 

Randomly oriented crystals/grains


d. 

Crystals/grains showing banding or alignment in one preferred direction


The correct answers are b and c.

3. Select all the correct observations of each textural feature of gabbro:

a. 

Interlocking crystals


b. 

Rounded grains


c. 

Randomly oriented crystals/grains


d. 

Crystals/grains showing banding or alignment in one preferred direction


The correct answers are a and c.

4. Gneiss has a banded crystalline texture and is therefore …

a. 

sedimentary


b. 

metamorphic


c. 

igneous


The correct answer is b.

5. Conglomerate has a fragmental texture and is therefore …

a. 

igneous


b. 

metamorphic


c. 

sedimentary


The correct answer is c.

6. Gabbro has a crystalline texture and lacks mineral alignment or banding and is therefore …

a. 

sedimentary


b. 

igneous


c. 

metamorphic


The correct answer is b.