lesson 2 minerals

Question 1

What is a solid? (refer to crystalline solids)

Answer 1

Crystalline solids have a set atomic structure, with its particles packed in a regular repating pattern, known as crystal lattice. Relatively rigid, resistant to changes in the shape and volume.

Question 2

What are crystals

Answer 2

Crystals are solids that are completely crystalline, often exhibiting crystal growth faces, which are the planes where new material has crystallised to form the crystal.

Question 3

What are the five properties of a mineral?

Answer 3

1. Naturally formed
2. Inorganic
3. Crystalline solid
4. Fixed structure
5. specific or slightly varied composition

Question 4

Minerals mainly form in three different ways, what are they?

Answer 4

1. Crystallisation from liquid magma:
   magma crystallises into a solid when it cools
   –> it is the process of atoms or molecules arranging themselves into well-defined, rigit crystal lattice and when energetic state is minimised, they form crystals.
2. Crystallisation from saturated liquid
   Minerals dissolved in liquid crystallise –> minerals remain after evaporation evaporates all the liquids
3. Biological processes
   Some organisms take in reasources and turn them into minerals.

Question 5

What minerals tells us? (four main things)

Answer 5

• -> identify environment they are formed in (extru, intru)
• -> temperature they are formed at (meta, melting)
• -> pressure (depths)
• -> dating minerals to relate to events in Earth’s history

Question 6

What is the name when the SAME ELEMENT can form different minerals?

Answer 6

Allotropes (don’t confuse with polymorphs (same chemistry, different crystal structure)

Question 7

What are the main 8 mineral properties?

Answer 7

Streak (colour in powdered), Lustre, Cleavage, Hardness, Acid reaction, colour, crystal habit, other

Question 8

What is streak?

Answer 8

Streak referes to the colour of th emineral in its powedered form , determined by scratching the mienral on a plate, often determined by the chemical composition of the mineral

Question 9

Lustre definition and what are the types?

Answer 9

Lusture describes how light interacts with the surface ot eh mineral.
Three main types:
–> metallic
–> dull
–> non-metallic (which includes the great majority of minerals particularly silicates)
- adamantine - like a diamond
- vitreous - like glass
- resinous, greasy - like resin , treep sap
- pearly - iridescent like pearls
- silky - like silk, associated with fibrous materials

Question 10

What is cleavage. Note that god damn rocks don’t exhibit cleavages, unless special

Answer 10

Planes of weakness in mineral’s crystal lattice cuasing it to breka easily along cleave planes when force is applied.

• -> example: sheet silicates (such as micas) which are very strongly bonded in the plane of the sheet, the bonds between the separate sheets however are very weak, which makes up for why they have ONE PLANE OF CLEAVAGE.
• -> most important defining characteristics when looking at the cleavage are the number of cleavage planes and the angle between these planes.
• -> cleavage is way that it HAS BEEN BROKEN

Question 11

Hardness?

Answer 11

refers to how hard it is to scratch a smooth mineral surface
–> molecular cohesiveness of a mineral and tested using Mohs hardness scale
Diamond 10 –> Gypsum 2 –> Talc 1