Lecture 2.1 - Igneous Rocks

Question 1

Definition of a rock

Answer 1

Collection of commonly associated minerals and/or mineraloids

Question 2

Steps in naming a rock (I, II, III)

Answer 2

Origin, composition, texture
- when giving origin, must include sub-division (ex: igneous intrusive)

Question 3

What is MSShOP

Answer 3

M - Minerals, chemistry, materials,
S- Size
Sh - Shape
O - Orientation
P - packing

Question 4

Characteristics of mafic rocks

Answer 4

• rich in Mg and Fe
• black/gray color

Question 5

Characteristics of Felsic rocks

Answer 5

• rich in feldspar and Si
• light color

Question 6

Characteristics of ultramafic rocks

Answer 6

• super rich in Mg
• green color

Question 7

Phaneritic

Answer 7

Larger visible grains

Question 8

How can you distinguish an intrusive igneous rock from an extrusive igneous rock?

Answer 8

If the rock is Phaneritic

Question 9

Granite

Answer 9

Igneous intrusive + Felsic + Phaneritic

Question 10

Gabbro

Answer 10

Igneous intrusive + mafic + Phaneritic

Question 11

Basalt

Answer 11

Igneous Extrusive + mafic +aphanitic + few vesicle

Question 12

Rhyolite

Answer 12

Igneous extrusive + Felsic + aphanitic

Question 13

Define aphanitic

Answer 13

No visible grains

Question 14

Define groundmass

Answer 14

Space between two crystals
- due to crystals forming million years ago then ruptured out onto surface where it cooled off rapidly = different sizes of crystals

Question 15

Define vesicle

Answer 15

Hole in the rock that used to be a gas bubble in the magma

Question 16

Define frothy

Answer 16

When vesicles meet

Question 17

Define porphyritic

Answer 17

Two different grain sizes

Question 18

Pumice

Answer 18

Felsic + Frothy

Question 19

Scoria

Answer 19

Mafic + frothy

Question 20

Peridotite

Answer 20

Igneous intrusive + Ultramafic + Phaneritic

Question 21

Obsidian

Answer 21

Glassy (any composition)