Practce for exam 2

Question 1

Where does rhyolite form?

Answer 1

Extrusively

Question 2

How can you tell pyroxene from amphibole in thin section?

Answer 2

Pyroxene has cleavage at 90 Amphibole has clevage at 60 and 120

Question 3

Name some minerals with high relief

Answer 3

Olivine, pyroxene, amphibole, calcite

Question 4

Name some minerals with low relief

Answer 4

Quartz, feldspars

Question 5

What is the gas that typically separates from the water deep in a geyser plumbing system causing it to erupt?

Answer 5

Water vapor

Question 6

What is the word used to describe the change in appearance as the microscope stage is rotated?

Answer 6

extinction

Question 7

At what point does graphic granite crystallize that causes the two minerals to crystallize at the same time to produce the unusual texture?

Answer 7

The eutectic point

Question 8

Is topaz an accessory or primary mineral in igneous rocks?

Answer 8

Accessory

Question 9

Is Olivine an accessory or primary mineral in igneous rocks??

Answer 9

Primary

Question 10

Is quartz an accessory or primary mineral in igneous rocks?

Answer 10

Primary

Question 11

Is albite an accessory or primary mineral in igneous rocks?

Answer 11

Primary

Question 12

Is nepheline an accessory or primary mineral in igneous rocks?

Answer 12

Primary

Question 13

Is ruitle an accessory or primary mineral in igneous rocks?

Answer 13

Accessory

Question 14

How would you tell plagioclase and pyroxene apart in plane polarized light in a thin section?

Answer 14

Pyroxene has high relief and a light green color. Plagioclase has low relief and a clear color.

Question 15

How would you tell plagioclase and pyroxene apart in crossed-nicols?

Answer 15

Pyroxene does not show twinning, and shows a wider variety of interference colors, plagioclase is only a grey/yellow.

Question 16

Where would a basalt form?

Answer 16

Hotspots and ocean ridges

Question 17

Where would a granite form?

Answer 17

A pluton.

Question 18

What parent rock melts to form the magma that erupts at a hotspot?

Answer 18

Peridotite

Question 19

What is the primary mineral in anorthosite?

Answer 19

Plagioclase

Question 20

Where does a rhyolite form?

Answer 20

A convergent plate boundary

Question 21

What are the main minerals in diorite?

Answer 21

Plagioclase and pyroxene

Question 22

When polarized light emanating from a light source below the microscope stage passes through a thin section, individual minerals cause the light wave to ___________.

Answer 22

refract.

Question 23

With the upper polarizing lens “in” isotropic minerals appear ____________.

Answer 23

dark

Question 24

With the upper polarizing lens “in” anisotropic minerals exhibit the property called

Answer 24

birefringence

Question 25

What type of lava is more viscous? dacitic or rhyolitic?

Answer 25

Rhyolitic

Question 26

In what "environment" is tuff formed?

Answer 26

pyroclastic flow

Question 27

An extrusive igneous rock that shows evidence of flow direction?

Answer 27

Ignembrite

Question 28

What type of volcanic eruptive process buried the roman city of Pompeii?

Answer 28

Pyroclastic flow.

Question 29

Main mineral in basalt?

Answer 29

Olivine

Question 30

As temperature increases solubility of a gas ________.

Answer 30

decreases

Question 31

As pressure increases solubility of a gas ___________.

Answer 31

Increases

Question 32

As pressure decreases solubility of a gas ____________.

Answer 32

decreases

Question 33

As temperature decreases solubility of a gas __________.

Answer 33

increases

Question 34

poikilitic

Answer 34

One large crystal forms around smaller crystals.

Question 35

cumulate

Answer 35

Igneous rocks formed by the accumulation of early-formed minerals by the action of gravity.

Question 36

ignimbrite

Answer 36

rock formed from welded pyroclastic flow. Explosive eruption.

Question 37

partial melting in the mantle produces

Answer 37

andesitic magma

Question 38

partial melting in the crust produces

Answer 38

granitic magma

Question 39

Is K-feldspar an accessory or primary mineral in igneous rocks?

Answer 39

primary

Question 40

Is feldspathoid an accessory or primary mineral in igneous rocks?

Answer 40

Primary

Question 41

Is mica an accessory or primary mineral in igneous rocks?

Answer 41

primary

Question 42

Is magnetite an accessory or primary mineral in igneous rocks?

Answer 42

accessory

Question 43

Is hematite an accessory or primary mineral in igneous rocks?

Answer 43

accessory

Question 44

Is zircon an accessory or primary mineral in igneous rocks?

Answer 44

accessory

Question 45

secondary minerals

Answer 45

form later from chemical reactions of hot water.

Question 46

Euhedral

Answer 46

Looks like a perfect or nearly perfect crystal

Question 47

Subhedral

Answer 47

Some sharp, straight edges

Question 48

Anhedral

Answer 48

irregular shape, edges not sharp

Question 49

pegmatic

Answer 49

>30 mm crystals

Question 50

What causes relief?

Answer 50

Differences in speed of light in different materials

Question 51

pleochroism

Answer 51

Light is absorbed differently by different crystal directions.

Question 52

Types of twinning displayed by plagioclase

Answer 52

simple albite pericline