Minerals and Rocks

Question 1

What is a mineral?

Answer 1

• Naturally-occurring
• Repeating crystalline structure
• Non organic carbon (doesn’t have carbon in it)
• “A solid, naturally occurring inorganic substance”
• Size doesn’t matter – minerals can be microscopic or enormous

Question 2

Why are minerals important?

Answer 2

• They are the building blocks of soil, rocks and mountains
• They provide the basic requirements for life on Earth
• They make up over 90% of the soil under our feet

Question 3

Is size a defining characteristic of minerals?

Answer 3

• No, minerals can be microscopic or enormous depending on how old they are because they grow

Question 4

What are the main mineral diagnostic properties?

Answer 4

• over 4000 minerals so we need to be able to identify them:
• Colour
• Lustre
• Hardness
• Cleavage
• Streak
• Crystal form
• Tenacity (malleable)
• Specific gravity/density
• Magnetism
• Reaction with HCl

Question 5

Why are colour and lustre good diagnostic properties of minerals?

Answer 5

• When minerals are created, they usually form with other minerals that need the same conditions to be made, therefore most minerals that form together with their colours re easily identifiable.
• There are three main categories of lustre: Metallic, Glassy or Earthy/dull. They help to identify the mineral based on how shiny it is

Question 6

How is hardness measured?

Answer 6

• Minerals are scored from 1 to 10 on the Mohs Hardness scale. A Diamond has a score of 10. At the other end of the scale, talc is the softest mineral with a hardness of 1.

Question 7

What is the Cleavage of a mineral?

Answer 7

• The tendency for a mineral to break along a plane

Question 8

What are the Streak and Crystal form mineral properties?

Answer 8

• Streak – the colour a mineral leaves when scratched on a black or white plate. e.g. hematite has a distinctive red streak
• Crystal form – the shape of the crystal. e.g. quartz is typically hexagonal

Question 9

What are the Tenacity and Specific gravity mineral properties?

Answer 9

• Specific gravity – mineral density. e.g. wolframite (dark colour) is about 3 times denser than quartz
• Magnetism – magnetic attraction. e.g. magnetite can attract metallic objects

Question 10

What is the Reaction with HCl mineral property?

Answer 10

• Reaction with HCl – some minerals fizz in contact with weak HCl. e.g calcite

Question 11

What are the Mineral Groups?

Answer 11

• The Silicates
• The Oxides
• The Carbonates
• The Sulphides
• Native elements

Question 12

What is “The Silicates” group of minerals?

Answer 12

• The Silicates are easily the most abundant minerals around us
• Common ones are Quarts, feldspar, clays and olivine
• The thing that links all the Silicate minerals is the chemical bond - SiO4

Question 13

What is “The Oxides” group of minerals?

Answer 13

• The “rusty” minerals.
• Very important and abundant secondary minerals (A secondary mineral is one resulting from the weathering of a primary mineral)
• Iron oxides key group and these include: hematite, magnetite, goethite
• Chemical bond – O/O2 /O3 /OH
• Magnetite, an Oxide, is one of the only magnetic minerals

Question 14

What is “The Carbonates” group of minerals?

Answer 14

• Often form in soils from carbonate in water and metals from soils
• Calcite is the main one
• Main mineral in limestone
• Chemical bond – CO3

Question 15

What is “The Sulphides” group of minerals?

Answer 15

• Our main sources of economic metals (Zinc, copper, lead)
• Metallic lustre
• Feel very dense (they are the densest minerals)
• Chemical bond - S/S2

Question 16

What is the “Native elements” group of minerals?

Answer 16

• Single element minerals

- E.g., gold, diamond

Question 17

What is a rock and what are the different types of rocks?

Answer 17

• Rocks are aggregates of one or more minerals
• There are 3 main types – 1. Igneous, 2. Metamorphic, 3. Sedimentary
• According to the rock cycle, any one type of rock can become another type
• At the start of the Earth 4.5 billion years ago, most rocks would have started out as igneous

Question 18

What is the rock cycle?

Answer 18

• The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock.

Question 19

What is the first part of the rock cycle?

Answer 19

• Igneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly. When it pours out on Earth’s surface, magma is called lava. Yes, the same liquid rock matter that you see coming out of volcanoes.

Question 20

What is the second part of the rock cycle?

Answer 20

• On Earth’s surface, wind and water can break rock into pieces. They can also carry rock pieces to another place. Usually, the rock pieces, called sediments, drop from the wind or water to make a layer. The layer can be buried under other layers of sediments. After a long time the sediments can be cemented together to make sedimentary rock. In this way, igneous rock can become sedimentary rock.

Question 21

What is the third part of the rock cycle?

Answer 21

• All rock can be heated. But where does the heat come from? Inside Earth there is heat from pressure (push your hands together very hard and feel the heat). There is heat from friction (rub your hands together and feel the heat). There is also heat from radioactive decay (the process that gives us nuclear power plants that make electricity). The heat bakes the rock.

Question 22

What is the fourth part of the rock cycle?

Answer 22

• Baked rock does not melt, but it does change. It forms crystals. If it has crystals already, it forms larger crystals. Because this rock changes, it is called metamorphic. Remember that a caterpillar changes to become a butterfly. That change is called metamorphosis. Metamorphosis can occur in rock when they are heated to 300 to 700 degrees Celsius.

Question 23

What is the fifth part of the rock cycle?

Answer 23

• When Earth’s tectonic plates move around, they produce heat. When they collide, they build mountains and metamorphose (met-ah MORE-foes) the rock.
• The rock cycle continues. Mountains made of metamorphic rocks can be broken up and washed away by streams. New sediments from these mountains can make new sedimentary rock. The rock cycle never stops.

Question 24

Study the diagram of the Rock cycle

Answer 24

https://docs.google.com/document/d/11SlS_6djE3BGAezT2-FeVRTdxG1P1jVyj-u3X2L5qDo/edit?usp=sharing

Question 25

What are the two types of Igneous rocks?

Answer 25

• IGNEOUS means “formed from cooling magma or lava”

- There are two types of Igneous rocks: Intrusive and Extrusive

Question 26

What are Intrusive Igneous rocks?

Answer 26

• E.g. Granite
• Igneous rocks are formed under the surface of the Earth (hence “Intrusive”). Because it’s formed under the Earth, it cools really slowly, thus giving the crystals time to grow and so Intrusive igneous rocks are characterised by large crystals
• Coarse grained interlocking crystals
• No layers or alignment of crystals
• Very hard/strong rocks

Question 27

What are Extrusive Igneous rocks?

Answer 27

• E.g. Basalt
• Extrusive igneous rocks are formed above the surface of the Earth and so they cool quickly, meaning that the crystals don’t have time to grow so extrusive igneous rocks have small crystals
• Fine grained interlocking crystals
• Generally no layers or alignment of crystals
• Can have air bubbles/vesicles
• Very hard/strong rocks

Question 28

Why is the difference between Intrusive and Extrusive Igneous rocks important?

Answer 28

• They are the two most common Igneous rocks and form most of the continental crust (Intrusive e.g. granite) and oceanic crust (Extrusive e.g. Basalt)
• Basalt is heavier than granite and so when they collide, the basalt goes underneath the continental plate.

Question 29

What does the mineral and chemical composition of igneous rocks depend on?

Answer 29

• The types of minerals in igneous rocks depend on the temperature at which the magma cools = BOWENS REACTION SERIES

Question 30

What is Bowen’s Reaction Series?

Answer 30

• Bowen’s reaction series can be defined as the crystallization sequence of magma as cooling occurs. It has two parts, the discontinuous series and the continuous series. Both branches progress with a drop in temperature.

Question 31

What elements are commonly found in magma at higher temperatures and why?

Answer 31

• High iron and magnesium content
• This is because Iron and Magnesium are quite dense and it takes really high temperatures for them to melt into a liquid
• Minerals that have a lot of Iron and Magnesium in them are called ferromagnesium minerals (just means that they have a high magnesium and iron content) and they give the mineral a distinctive colour (usually dark)

Question 32

What elements are commonly found in magma at lower temperatures and why?

Answer 32

• High feldspar and silicon content

Question 33

Study the diagram of the Bowen’s Reaction Series

Answer 33

https://docs.google.com/document/d/11SlS_6djE3BGAezT2-FeVRTdxG1P1jVyj-u3X2L5qDo/edit?usp=sharing

Question 34

What are Ultramafic and Mafic rocks?

Answer 34

• Ultramafic Rock: An igneous rock with a very low silica content and rich in minerals such as hypersthene, augite, and olivine (highest temperature required)
• Mafic Rock: Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron (high temperature required but not as much as Ultramafic)

Question 35

What are Intermediate and Felsic rocks?

Answer 35

• Intermediate rocks are roughly even mixtures of felsic minerals and mafic minerals
• Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Felsic rocks are usually light in color and have specific gravities less than 3.

Question 36

What type of magma forms a granite rock whose main minerals are K-feldspar and quarts?

Answer 36

• Felsic magma

Question 37

What type of magma forms a Basalt rock whose main minerals are Pyroxene and olivine?

Answer 37

• Mafic magma

Question 38

What are Metamorphic rocks?

Answer 38

• E.g. Gneiss
• Rocks that form from pressure - deformed rocks - doesn’t need to have extremely high temperatures
• Signs of stress/trauma e.g. folding, intersecting quartz veins
• Can have repetitive layering/alignment of minerals called FOLIATION (common in gneiss)
• Very hard/strong rocks

Question 39

What are Sedimentary rocks?

Answer 39

• Made by gentle processes, like sediments, either in a river or in the ocean, gradually getting deposited down over time and as they do this it forms layers
• Fossils are found in these rocks because they are the only ones that don’t undergo harsh processes to form them
• Often exhibit layering from deposition of sediments
• Can be brittle/soft
• Formed by weathering of parent rock (either metamorephic or igneous) and subsequent lithification

Question 40

What is Lithification?

Answer 40

• The process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock

Question 41

What are some areas that rocks and minerals are used in?

Answer 41

• Food production: Apart from nitrogen, all of our major fertiliser compounds (P, K, Fe, Ca, Mg) are mined from geological sources
• Pollution Control: Certain types of minerals (e.g. zeolites) have the ability to retain chemical pollutants and they are used in various industries for pollution control
• Climate Change: One of the most abundant minerals on Earth – olivine - has been shown to lock up atmospheric carbon as it weathers