Rock Types

Question 1

What is a mineral

Answer 1

A natural, inorganic substance which has a definite chemical composition and arranged atomic structure

Question 2

What is a rock

Answer 2

aggregates of one or more mineral. The properties of rock are determined by the minerals and the arrangement of said minerals relative to each other.

Question 3

what is the origin of the 3 rock types

Answer 3

Igneous - crystallised from magma
sedimentary - erosional debris from other rocks
metamorphosis- rocks altered by heat and/or pressure

Question 4

What environment are the 3 rock types found in

Answer 4

Igneous - underground or in lava flows
Sedimentary - deposition basins often underwater
metamorphosis - mostly deep inside mountain chains

Question 5

What are the rock textures of the 3 rock types

Answer 5

Igneous - mosaic of interlocking crystals
sedimentary- mostly granular and cemented
metamorphosis - mosaic of interlocking crystals

Question 6

What are the rock structures of the 3 rock types

Answer 6

Igneous - massive and structureless
sedimentary- bedded and layered
metamorphosis - crystals oriented due to pressure

Question 7

What are the rock strengths of the 3 rock types

Answer 7

Igneous - very strong and uniform
sedimentary- low and can have planar weakness
metamorphosis - high variability and can have planar weakness

Question 8

what are 3 major examples of each rock type

Answer 8

Igneous - basalt, granite, granodiorite
sedimentary- sandstone, limestone, clay
metamorphosis - gneiss, schist, slate

Question 9

What is cleavage and what is fracture

Answer 9

Cleavage is a preferential split. It will break in a particular plane which will leave a perfectly flat surface. Rocks don’t have cleavage and will instead have fractures which is a lack of cleavage, resulting in a undulating surface when broken

Question 10

What is the tenacity of a rock

Answer 10

The response of a rock on sudden impact - is it brittle or malleable

Question 11

What are the two classes of rock forming minerals

Answer 11

silicate minerals and non silicate minerals (carbonates, oxides, halides, sulphides, sulphates and phosphates)

Question 12

What are the main features and properties of the mica group

Answer 12

planar sheets arranged in layers so water can easily seep in to cause weathering. Has perfect cleavage parallel to the basal plane,

Question 13

What happens in the weathering of mica

Answer 13

Metal ions are removed from the mineral and dissolved

Question 14

What happens in the weathering of feldspar

Answer 14

Mineral reacts with water’s H+ ions. This requires flowing water to introduce new H+ ions

Question 15

What are the columns of magma that rise through the earth’s crust and their horizontal counterpart

Answer 15

Dykes and sills

Question 16

What are felsic and mafic igneous rocks

Answer 16

Felsic is acidic, meaning a higher silica content. Mafic is basic meaning higher metal oxide content

Question 17

Why do intrusive igneous rocks have larger grains than extrusive igneous rocks

Answer 17

Intrusive igneous rocks, those that are formed within the earth’s crust, cool down slower so the grains have time to grow large

Question 18

What is porphyritic and how does it occur

Answer 18

Large grains surrounded by smaller grains. Occurs when intrusive rocks are suddenly ejected while still cooling

Question 19

Why is quartz hardest to weather while olivine and pyroxene easiest to weather

Answer 19

quartz has the most complex structure and possesses more covalent bonds. Olivine and pyroxene have simpler structures with more ionic bonds

Question 20

What are anhedral and euhedral shapes and what causes them

Answer 20

euhedral means distinct shapes while anhedral is non distinct shapes. The minerals that solidify first tend to have euhedral shapes while those that solidify last have anhedral shapes as they are left with the remaining volume so don’t have the freedom of choosing their shape. Therefore, higher melting point (so solidifies earlier) means more euhedral

Question 21

What are the two types of sedimentary rock

Answer 21

Clastic (exogenic) and non clastic (endogenic)

Question 22

What determines [ ]of sedimentary rocks:
grain size
grain roundedness
sorting/ grading

Answer 22

grain size - energy of the deposition method. More energy means larger grains can be transported then deposited
grain roundedness - distance from mother rock. Further away means more weathering so more rounded
sorting/grading - variation in depositional events

Question 23

What is lithic/arkose/quartz arenite/graywacke sandstone

Answer 23

High in rock fragments, high in feldspar, pure quartz, high in matr

Question 24

what is lithification

Answer 24

The transformation of sediments such as sand, mud etc into rock through pressure and temperature. Mud becomes shale, sand becomes sandstone, gravel becomes conglomerate

Question 25

What is diagenesis

Answer 25

all the processes involved in transforming sediment into rocks. Includes compaction (the removal of water in between sediments) and cementation (involves ions precipitating to form new crystalline material between sedimentary grains)

Question 26

What is the dott classification

Answer 26

A classification of sandstone that classifies sandstone based on main constituent (quartz, feldspar etc) and matrix (the glue that holds the fragments together) percentage

Question 27

What is anisotropy and isotropy

Answer 27

Properties of a rock that signify heterogeneity and homogeneity in different directions. Anisotropic rocks could be stronger in certain directions for example while isotropic rocks will exhibit the same properties in all directions

Question 28

what is the difference between clastic and non clastic sedimentary rocks

Answer 28

Clastic sedimentary are formed when bits of other rocks are weathered and deposited. Non clastic rocks form from the evaporation of water or from remains of plants/animals.

Question 29

What happens to the grains in metamorphic rocks

Answer 29

due to heat and pressure, the minerals (the grains) shift and separate then recrystallise, leaving no void spaces

Question 30

What are the 3 types of metamorphic rock and what distinguishes them

Answer 30

thermal/contact (temperature), dynamic/dislocation(stress), regional(temperature + stress). Note dynamic occurs when two mountains move into each other at shallow depths

Question 31

What happens when more energy is applied to metamorphic rocks

Answer 31

They have increased crystal size (so are more shiny) and have more foliation (banding/layering)

Question 32

What causes foliation

Answer 32

Heat and pressure

Question 33

Why can't granite become slate and mudstone become gneiss

Answer 33

Different rocks require different amounts of energy to metamorphize. Granite needs too much energy to metamorphize so can't become slate, while mudstone will melt instead of metamorphize at the energy required to become gneiss

Question 34

What is marble a metamorphosis of

Answer 34

Limestone

Question 35

What are the three metamorphic rocks that clays, silts and volcanic ash can become in order of energy

Answer 35

slate, phyllite, schist