Minerals Flashcards
What is an element?
A substance made up of only one type of atom
What are 8 elements and their abundance in the Earth’s crust?
Oxygen - 47%
Silicon - 28%
Aluminium - 8%
Iron - 5%
Calcium - 4%
Sodium - 3%
Potassium - 3%
Magnesium - 2%
Other elements - <1.5%
What is a mineral?
The things that rocks are made up of. A substance made of different elements
What are 5 rules a substance must follow to be considered a mineral?
- Must be solid at normal Earth conditions
- Must be naturally occurring
- Must be inorganic
- Must have a fixed chemical formula
- Must have specifically arranged atoms
What are minerals formed from?
Minerals form from molten material
What determines the size of crystals?
Cooling rate.
Slow cooling = larger crystals
Fast cooling = smaller crystals
Is glass a mineral, and why?
No. Cooled so quickly that atoms do not have enough time to rearrange themselves - breaching rule 5 (specifically arranged atoms)
How is the size and shape of mineral crystals determined? (Not cooling rate)
Crystals grow from the centre outwards by adding faces. Crystals have a definite shape, and the angle between the faces always remains the same.
If a crystal forms in a void or cavity, it will have a well-defined shape. If a mineral crystal forms next to another, it will form a grain boundary, and the shape will look irregular
What is a rock?
An aggregate of one or more minerals
What is a “habit” when describing a crystal?
It’s shape
What are the 7 possible habits of a crystal?
Isometric, Hexagonal, tetragonal, orthorhombic, monoclinic, triclinic, trigonal
What are some examples of isometric crystals?
Garnet, Diamond, Gold
What are some examples of Hexagonal crystals?
Calcite, Apatite, Tourmaline
What are some examples of tetragonal crystals?
Apophyllite, Rutile, Zircon
What are some examples of orthorhombic crystals?
Olivine, Topaz, Cementite
What are some examples of monoclinic crystals?
Gypsum, Azurite, Orthoclase
What are some examples of triclinic crystals?
Kyanite, Rhodonite, Axinite
What are some examples of trigonal crystals?
Ruby, Agate, Tigers Eye
What does it mean identify a mineral’s colour?
Different minerals have different colours, but some minerals share the same colour. It is determined by the arrangement of atoms (light reflection)
What does it mean to identify a mineral’s streak?
Residue left by a mineral when scraped across a porcelain streak plate. Streak is the colour of a mineral when it is broken up or powdered (scraped). The test can only be done if the mineral is softer than porcelain
What does it mean to identify a mineral’s lustre?
How well a mineral reflects light. Words used to describe lustre include: metallic, Vitreous, silky, pearly.
Most rock-forming minerals are Vitreous
What does it mean to identify a mineral’s shape?
Different crystals have different shapes/Habits. This is determined by by the arrangement if atoms or crystal structure
What does it mean to identify a mineral’s cleavage?
Some minerals have cleavage plains, these are plains of weakness (e.g. biotite mica)
What does it mean to identify a mineral’s hardness?
Different crystal have differen5 hardness. Hardness is measured from 1-10 on ‘Moh’s hardness scale’(1 softest, 10 hardest)
What does it mean to identify a mineral’s desnity?
Different minerals have different densities. Amount of mass per unit volume (gcm-³)
What does it mean to identify a mineral’s reaction with acid?
Some minerals will react with acid. If a mineral reacts with acid, fizzing/bubbling will be observed. Carbonate minerals react with acid.
In geology - we use weak HCl acid (hydrochloric)
What are the 11 rock-forming minerals we learnt about (the big table)?
Quartz, orthoclase feldspar, plagioclase feldspar, biotite mica, muscovite mica, augite, hornblende, Olivine, Calcite, garnet, kyanite
What are the characteristics of quartz?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Trigonal
White/grey or transparent
Hardness - 7
Doesn’t have cleavage plain. It has a conchoidal fracture
It is vitreous
Density of 2.65gcm-³
Colourless streak
What are the characteristics of orthoclase feldspar?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Triclinic
Peach/pink
Hardness 6.5
2 cleavage please near 90°
It is vitreous
Density 2.7gcm-³
White streak
What are the characteristics of
Plagioclase feldspar?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Triclinic
White/grey or blue/grey
Hardness - 6
2 cleavage plains near 90°
Vitreous
2.7gcm-³
White streak
What are the characteristics of biotite mica?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Monoclinic Hexagonal
Black, dark brown
Hardness - 3
Perfect cleavage in one direction
Vitreous-pearly
3gcm-³
White/grey streak
What are the characteristics of muscovite mica?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Monoclinic hexagonal
White
Hardness - 3
Perfect cleavage in one direction
Vitreous pearly
3gcm-³
White/grey streak
What are the characteristics of augite?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Monoclinic
Dark green - black
Hardness - 6
2 plains of cleavage near 90°
Vitreous usually, sometimes dull or resinous
3.5gcm-³
White streak
What are the characteristics of hornblende?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Diamond-shaped
Green-black
Hardness - 6
2 cleavage plains at 60°
Vitreous, metallic
3gcm-³
Pale grey/white streak
What are the characteristics of olivine?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Hexagonal
Green/yellow
Hardness 7
Poor cleavage, conchoidal fracture
Vitrous
3.5gcm-³
White/colourless/grey streak
What are the characteristics of calcite?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Trigonal
Colourless or white
Hardness 3
3 perfect cleavage plains
Vitreous
2.7gcm-³
Colourless or white streak
What are the characteristics of garnet?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Rhombic dodecahedron
Deep red to brown
Hardness 7
No cleavage plains, conchoidal fracture
Vitreous
4gcm-³
White streak
What are the characteristics of kyanite?
(Habit, colour, hardness, cleavage, lustre, density,and streak)
Long narrow blades (or slats)
White/blue/grey
Hardness 4.5-7
2 cleavage plains at 79°
Vitreous or pearly
3.5gcm-³
White streak
What is moh’s hardness scale, in order?
Talc
Gypsum
Calcite
Fluorite
Apatite
Feldspar
Quartz
Topaz
Corundum
Diamond
What is the mnemonic for remembering moh’s hardness scale?
The Green Cheese Flakes Awfully, Furthermore, Question The Cheesy Doritos
How can we test the hardness of minerals with a hardness >2?
It can be scratched with a fingernail
What do we test the hardness of something with a hardness of 3?
It can be scratched by a 2p coin
How do we test the hardness of a mineral with hardness 4-5?
It can be scratched with a steel blade
How do we test the hardness of a mineral with hardness 6?
It can sometimes be scratched by a steel blade
How do we test the hardness of a mineral with hardness 7+?
It can scratch glass
How do you carry out test a mineral’s hardness using a kit?
Find a flat surface on the unknown mineral
Take the reference material and find a sharp edge or corner
Drag the reference material across the unknown mineral
If a scratch is produced on the unknown mineral, it’s softer than the reference material (and vice versa)
Select the next hardness up or down the scale and repeat
What is the equipment needed to measure mineral density?
Balance (mass)
Measuring cylinder / displacement can / eureka can (volume)
Sample material (mineral/rock)
Water
What is the method for measure mineral density?
Zero the balance
Place sample on the balance and record the mass (g)
Put a known volume of water in measuring cylinder
Place the same in the water
Record the new water level reading
Difference/displacement = volume of same
1ml = 1cm³
1ml = 1g
What are the two most abundant elements in the earth’s crust, and their %s?
Oxygen and Silicon (47% and 28%)
What is a cation?
A positively charged ion that would be attracted to the cathode in electrolysis
What is an anion?
A negatively charged ion that would be attracted to the anode in electrolysis
Does Silicon become a cation or anion when reacting with oxygen, and what is its charge?
Silicon is a cation.
4+
Does oxygen become a cation or an anion when reacting with silicon, and what is its charge?
Oxygen is an anion.
2-
What is a silica tetrahedron?
The building blocks of all silicate minerals.
Silicon and oxygen atoms are attracted to each other because they can share electrons.
Sharing electrons form covalent bonds.
A tetrahedron is a triangle pyramid.
A silica tetrahedra is made of 1 silicon atom (centre) and 4 oxygen atoms (corners)
Have an overall charge of 4-
What are single tetrahedra?
Simplest silicate mineral structure.
An example of a mineral with this structure is olivine
The tetrahedra are not directly bonded to each other
Other elements join or link them together
What are silica chains?
Silica tetrahedra can form chains when each tetrahedra shares 2 bridging oxygen atoms.
Chains have not achieved a balanced charge.
Pyroxene is an example of a mineral with a chain structure
What are double silica chains?
When two chains join together.
Some silica tetrahedra share 3 bridging oxygen, and some share 2.
An example of a mineral with this structure is hornblende
What are silica sheets?
Form when each silica tetrahedra have 3 bridging oxygens
An example of mineral with a sheet structure is mica
Usually have weak bonds that hold the sheets together
Have a good cleavage
What are silica frameworks?
All 4 oxygens are shared by adjacent tetrahedra
Tend to be strong and hard due to strong bonds in all direction
An example of a mineral with a framework structure is quartz
What is polymerisation? (Silica tetrahedra)
A polymer is a chain of the same thing
The process where they join is polymerisation
Silica tetrahedra form polymerase by oxygen bridging
The more polymerisation in a lava or magma, the slower the flow
What is a sedimentary rock?
A rock composed of fragments that have been deposited, compacted and cemented
How are sedimentary formed?
Most sediments are the result of weathering (breaking up) and erosion (transport)
Fragments of rock or ions in a solution are transported by water or wind (energy)
As energy levels decrease, sediment is deposited
Burial causes compaction
Sedimentary rocks usually form in layers
Sedimentary rocks sometimes contain fossils or trace fossils
If a rock contains a fossil, you can almost certain it is Sedimentary (in AS)
What is the name of the process where sediment becomes a rock?
Diagenesis
What is an igneous rock?
A rock that has crystallised from a magma (or lava)
How are igneous rocks formed?
Composed of interlocking crystals.
Either intrusive or extrusive. The slower the cooling process, the larger the crystal size
What are intrusive igneous rocks?
Magma formed igneous rocks are formed in the Crust
What are extrusive igneous rocks?
Lava formed igneous rocks are cooled on the surface
What is a metamorphic rock?
A rock formed by the recrystallisation of other rocks in the solid state due to pressure, temperature or both
How are metamorphic rock formed?
Recrystallation in solid solution.
Minerals in the parent rock recrystallise to form new rocks. Composed of interlocking crystals
What is regional metamorphism?
Large scale pressure (which = heat). Usually at convergent boundary
What is contact metamorphism?
Rocks are in contact or close to a heat source
What is the texture of igneous, sedimentary, and metamorphic rocks?
Igneous - crystalline. Interlocking crystals
Sedimentary - fragmental
Metamorphic - crystalline. Interlocking crystals
Is there mineral alignment in igneous, sedimentary, and metamorphic rocks?
Igneous - no
Sedimentary - not often
Metamorphic - often
What are the main minerals found in igneous, sedimentary, and metamorphic rocks?
Igneous - quartz, Olivine
Sedimentary - clay, mica
Metamorphic - garnet
What is the formation of igneous, sedimentary, and metamorphic rocks?
Igneous - crystallised from magma
Sedimentary - deposition of rock or mineral fragments
Metamorphic - recrystallisation of other rocks
What are the features (beds) of igneous, sedimentary, and metamorphic rocks?
Igneous - no beds
Sedimentary - horizontal beds
Metamorphic - no beds
Can fossils be found in igneous, sedimentary, and metamorphic rocks?
Igneous - none
Sedimentary - yes, not always
Metamorphic - rarely (look deformed)
How easy is it to break igneous, sedimentary, and metamorphic rocks?
Igneous - don’t split easily
Sedimentary - easier to break. Sometimes hard (never as much as igneous)
Metamorphic - hard to break. Sometimes alignment means it splits into layers (slate)
What is the mnemonic used to remember the elements in the crust?
Ocean sediments are important components supporting plate movements
