An introduction to the properties of rocks and their composition

Question 1

Where do rocks come from?

Answer 1

• Formed from cooling magma
• From igneous or sedimentary
• Metamorphism

Question 2

What is involved in the global tectonic?

Answer 2

• Tectonic drift
• Convection currents - plates slides on top and past each other
• Elevated temps and higher pressures - metamorphism

Question 3

What are the 3 types of rocks?

Answer 3

• Sedimentary
• Igneous
• Metamorphic

Question 4

What are minerals?

Answer 4

Naturally occurring inorganic substance which has a definite chemical composition and presents an ordered atomic arrangement.

Question 5

What are rocks?

Answer 5

Any naturally occurring aggregate of one or more mineral or mineraloid matter.

Question 6

How do igneous rocks form

Answer 6

Underground and crystallised from molten magma

Question 7

What are features of igneous rocks?

Answer 7

• Uniform high strength
• Massive
• Mosaic of interlocking crystals
  e.g., granite, basalt

Question 8

How are sedimentary rocks formed?

Answer 8

Erosional debris on Earth’s surface and deposition basins; mainly in the sea

Question 9

What are features of sedimentary rocks?

Answer 9

• Granular and cemented
• Layered, bedding planes
• Low variability rock strength
  e.g., sandstone, clay

Question 10

How are metamorphic rocks formed?

Answer 10

• Altered by heat and/or pressure
• Deep inside mountain chains

Question 11

What are features of metamorphic rocks?

Answer 11

• Mosaic of interlocking crystals
• High variability in strength
  e.g., Gneiss, slate

Question 12

What are some characteristics of minerals?

Answer 12

1. Colour
2. Lustre (appearance/ reflectance)
3. Form (shape/ grouping/ clustering)
4. Hardness (resistance to abrasion)
5. Cleavage (preferential split)
6. Fracture (nature of broken surfaces – lack of cleavage)
7. Tenacity (response upon sudden impact i.e. malleable vs brittle)
8. Specific gravity

Question 13

What does cleavage mean?

Answer 13

The tendency of a mineral to break along flat planar surfaces as determined by the structure of its crystal lattice.

Question 14

What are the two mineral classes?

Answer 14

1. Silicate
2. Non-silicate

Question 15

What are the mineral groups and their colours?

Answer 15

1. Olivine - pale green
2. Pyroxene - dark colour (black)
3. Amphibole - various dark colours
4. Mica - vitreous
5. Feldspar - pink, white, colourless
6. Silica - colourless

Question 16

What types of rock structures are there?

Answer 16

• Crystalline
• Polycrystalline

Question 17

What does polycrystalline mean?

Answer 17

Consisting of many crystalline parts that are randomly oriented with respect to each other.

Question 18

What does amorphous mean?

Answer 18

When you cool something down very quickly

Question 19

What type of mineral is mica?

Answer 19

Silicate

Question 20

What are two examples of minerals in the mica group?

Answer 20

1. Muscovite
2. Biotite

Question 21

What happens when mica is weathered?

Answer 21

Metal ions are removed from the mineral. Reaction results in soluble metal ions and clay minerals.

Question 22

What type of mineral is feldspar?

Answer 22

Silicate

Question 23

Where is feldspar’s found?

Answer 23

Earth’s continental crust

Question 24

What are two very common variations of feldspar?

Answer 24

1. Alkali feldspar (Pink or white)
2. Plagioclase feldspar (White, colourless or grey)

Question 25

What are the types of igneous rocks?

Answer 25

- Extrusive - Intrusive - Felsic - Mafic

Question 26

What does extrusive mean?

Answer 26

Produced when magma exits and cools above (or very near) the Earth's surface - cool quickly - small crystals

Question 27

What does intrusive mean?

Answer 27

Also called plutonic rock, formed from magma forced into older rocks at depths within the Earth's crust, which then slowly solidifies below the Earth's surface, though it may later be exposed by erosion - large crystals

Question 28

What are the two main type of eruptions which cause extrusive igneous rocks?

Answer 28

1. Fissure eruptions - low viscosity - fine grained rock 2. Central eruptions - ejection of lava and ash + broken rock

Question 29

What does euhedral mean?

Answer 29

Well defined shapes

Question 30

What does anhedral mean?

Answer 30

Imperfect shape

Question 31

What textures/ structures can you have?

Answer 31

- Equigranular - Aphanitic = can't see anything - Inequigranular - Porphyritic = large crystals surrounded by small crystals - Glassy - Vesicular - cavities

Question 32

What are the three types of magma?

Answer 32

Basaltic, andesitic, and rhyolitic

Question 33

What is Bowens reaction series?

Answer 33

Bowen's Reaction Series describes the temperature at which minerals crystallize when cooled, or melt when heated

Question 34

What is Goldichs dissolution series?

Answer 34

This series summarises the relative resistance to weathering of the common rock-forming silicates