G120 Quiz Vocab

Question 0

What are intermediate igneous rocks?

Answer 0

Intermediate composition is a term used to describe igneous rocks or magma that are have roughly even amounts of felsic and mafic minerals, and as such are moderately colored, and have mid levels of silicon content. MCI of 16-45%.

Question 1

What are felsic igneous rocks?

Answer 1

Felsic is a term used to describe igneous rock or magma that are composed mainly of light colored silicates; primarily quartz, k-spar, and plagioclase.

They have high silicon content, and low melting points. MCI of 0-15%.

Felsic, from feldspar and silica (quartz).

Question 2

What are mafic igneous rocks

Answer 2

Mafic is a term used to describe igneous rock or magma that have a MCI of 46-85%. Darker from their high iron and magnesium content, they are typically denser than lighter colored igneous rocks, have lower percentages of silicon, and a high melting point.

Mafic, from MAGnesium and Ferrum (iron).

Question 3

What are ultramafic igneous rocks?

Answer 3

Ultramafic igneous rocks have a MCI of 85-100%, so they typically appear very dark green to black. Olivine and pyroxene are the two most abundant minerals.

Question 4

What is a phaneritic texture?

Answer 4

Igneous rocks with a phaneritic texture have large visible crystals, and cooled slowly in the earth.

Question 5

What is an aphanitic texture?

Answer 5

Igneous rocks with an aphanitic texture have small crystals that aren’t visible with the naked eye or a hand lens, and cooled relatively quickly near the surface.

Question 6

What is a porphyritic texture?

Answer 6

Igneous rocks with a porphyritic texture have large visible crystals in a matrix made up of finer crystals. They are indicative of a rock slowly cooling, then be transported to an area that cooling happens more rapidly.

Question 7

What is a pegmatitic texture?

Answer 7

Igneous rocks with a pegmatitic texture have large visible crystals, typically 2.5cm or larger. They are typically the result of a presence of liquid volatiles, not necessarily rapid cooling.

Question 8

What is a glassy texture?

Answer 8

Igneous rocks with a glassy texture have cooled very quickly, even before ions can form an orderly crystalline structure. They can also result from the cooling of very viscous magma.

Question 9

What is a vesicular texture?

Answer 9

Igneous rocks with a vesicular texture have had gas bubbles trapped in the magma as it cools, creating voids, hollows, and airy, frothy texture.

Question 10

What is a pyroclastic or fragmental texture?

Answer 10

Igneous rocks with a pyroclastic texture are a consolidation of individual rock fragments that are ejected during an eruption. They can be very fine ash, molten blobs, or angular blocks torn from the vent.

Question 11

What does intrusive mean?

Answer 11

Intrusive is another name for phaneritic igneous rocks; that is, rocks with visible crystals that have cooled slowly underground.

Question 12

What does extrusive mean?

Answer 12

Extrusive is another name for aphanitic igneous rocks; that is, rocks without visible crystals that have cooled quickly at or near the surface.

Question 13

What does unneven cooling mean?

Answer 13

Igneous rocks that cooled unevenly have large crystals in a matrix of smaller, non-visible crystals. It is a synonym of porphyritic.

Question 14

What is a mettalic luster?

Answer 14

Minerals with a metallic luster (M) reflect light in a way similar to metals.

Question 15

What is a non-metallic luster?

Answer 15

Minerals with a nonmetalic luster (NM) reflect light in a way unlike metals.

Question 16

Describe the Mohs Hardness Scale

Answer 16

10 Diamond
7 Quartz
6.5 Streak Plate
5.5 Glass or steel masonry nail
4.5 wire (iron) nail
3.5 brass
2.9 copper penny
2.5 fingernail
2 gypsum
1 talc

Question 17

Describe streak color.

Answer 17

Streak is the color of a substance once it has been scratched on a streak plate or ground to a fine powder, and is a good way to determine luster. A mineral harder than a streak plate will create a white streak.

Question 18

Describe cleavage.

Answer 18

Cleavage is the tendency of minerals to break along flat, parallel surfaces.

Excellent cleavage reflects light in one direction from a large, flat parallel surface.

Good cleavage reflects light in one directions from a set of many small, obvious parallel surfaces.

Poor cleavage reflects light from a set of small, difficult to see, flat parallel surfaces.

Question 19

What is detrital composition?

Answer 19

Sedimentary rocks that have a detrital composition are composed of rock fragments and mineral grains that were worn away from the landscape.

Question 20

What is biochemical composition?

Answer 20

Sedimentary rocks that have a biochemical composition are composed of whole and partial remains of organisms, such as shells and plant fragments.

Question 21

What is chemical composition?

Answer 21

Sedimentary rocks that have a chemical composition are composed of chemical residues and intergrown crystals precipitated from aqueous solutions.

Question 22

Describe gravel-sized grains.

Answer 22

Visible grains larger than 2mm in diameter.

Question 23

Describe sand-sized grains.

Answer 23

Visible grains that have a gritty feel.

0.0625 mm to 2 mm.

Question 24

Describe silt-sized grains.

Answer 24

Grains that are usually too small to see, but may have a slight gritty feeling when rubbed.

0.0039 mm to 0.0625 mm.

Question 25

Describe clay-sized grains.

Answer 25

Grains that are too small to feel and have a smooth feel, similar to chalk dust.

Less than 0.0039 mm.

Question 26

Describe a microcrystalline structure.

Answer 26

Sedimentary rocks with a chemical composition containing crystals that are too small to distinguish.

Question 27

Describe a crystalline structure.

Answer 27

Sedimentary rocks with a chemical composition containing crystals that are clearly visible.

Question 28

Describe roundness.

Answer 28

Very angular (VA)
Subangular (SA)
Subround (SR)
Well rounded (WR)

Question 29

Describe sorting.

Answer 29

Sorting is a description of the degree to which one size sediment has been separated from others, and is usually indicative of the energy of the environment.

Poorly sorted
Moderately sorted
Well sorted

Question 30

What are ooids?

Answer 30

Small spherical grains resembling pearls.

Question 31

What does fissile mean?

Answer 31

It is the tendency to split into thin sheets along planes of weakness. Common in shale and slate.

Question 32

What does foliated mean?

Answer 32

Metamorphic rocks with a foliated texture have layering and parallel plains.

Question 33

What does slaty mean?

Answer 33

Metamorphic rocks with a slaty cleavage have very flat foliations, like slate.

Question 35

Describe fracture.

Answer 35

And break in a rock or mineral that does not occur along a cleavage plane. They are normally not flat and never occur in parallel sets.

Question 36

What is a phyllite texture?

Answer 36

Metamorphic rocks with a phyllite texture have a distinct wavy texture, and are called phyllite.

Question 37

What is schistosity?

Answer 37

Metamorphic rocks that show schistosity have glittery scales of visible minerals and are called schist.

Question 38

What is gneissic banding?

Answer 38

Metamorphic rocks with gneissic banding have foliation with alternating bands of light and dark color.

Question 39

What does nonfoliated mean?

Answer 39

Metamorphic rocks that are nonfoliated have no obvious layering.