Rocks And Minerals

Question 1

What is a mineral?

Answer 1

A naturally occurring chemical compound with a particular atomic structure and chemical formula

Question 2

What are the key physical properties of minerals that can be used in their identification? What controls these properties?

Answer 2

Colour, lustre, hardness, habit, cleavage, fracture, density, taste, smell, magnetic, effervescence and radioactivity. These are controlled buy the chemical formula

Question 3

What are some minerals you should be familiar with?

Answer 3

Silicates: quartz, feldspar, mica, pyroxene, amphibole, olivine, clay minerals and garnet
Non-silicates: calcite, Dolomites, gypsum, halite, magnetite, pyrite and hematite

Question 4

What four mechanisms result in the formation of minerals?

Answer 4

Cooling and crystallisation, evaporation and precipitation, solid state transformation and secretion by organisms

Question 5

How are minerals grouped according to their chemical composition?

Answer 5

Silicates, carbonates, oxides, sulphides, sulphates, halides, hydroxides and native elements

Question 6

What is quantitatively the most common group of minerals in the Earths crust?

Answer 6

Silicates

Question 7

What is the building block of all silicate minerals?

Answer 7

Silicon and oxygen

Question 8

How do the arrangement of the tetrahedra affect the structure of silicate minerals, and what are common mineral examples of each type?

Answer 8

It affects the total ratio of silicon: oxygen, affecting the density, hardness and other properties of the minerals. There are single chain, double chain, sheet and 3D structures that can be formed.

Question 9

What is fractional crystallisation and how does it control the silicate mineral formed?

Answer 9

The separation of minerals as they move away from a heat source and cool, crystallising in order of melting points, it controls the silicate formed by changing the chemical composition of the melt as other minerals precipitate out of the solution

Question 10

What is a rock?

Answer 10

An aggregate of mineral grains, or in some cases, non-mineral solid matter (glass, fossils)

Question 11

How are rocks classified? What are the three common types of rock?

Answer 11

Classified by origin, Igenous, sedimentary and metamorphic

Question 12

What is the main difference between igneous, metamorphic and sedimentary rocks in terms of their origin?

Answer 12

Igneous is formed by cooling of molten magma, sedimentary is formed by the erosion and deposition of pre-existing rock and metamorphic is formed by solid-state change of Igenous rocks

Question 13

How can texture be used to distinguish between igneous, sedimentary and metamorphic rock?

Answer 13

Igneous rocks are crystalline, sedimentary are non-crystalline and layered, and metamorphic is crystalline and layered

Question 14

What are the most common minerals found in igneous, metamorphic and sedimentary rock?

Answer 14

Quartz

Question 15

How do intrusive and extrusive igneous rocks form?

Answer 15

Intrusive igneous rocks cool within the Earth’s crust to solidify, whereas extrusive undergo rapid cooling at the surface (lava)

Question 16

How are rocks classified?

Answer 16

Clastic (formed by physical processes) and non-clastic (formed by biological or chemical processes)

Question 17

What controls the texture of an igneous rock?

Answer 17

The rate of cooling, slow cooling (intrusive) forms larger crystals, whereas rapid cooling forms finer grains

Question 18

What is meant by mafic and felsic? What minerals do these rocks contain?

Answer 18

Mafic is rich in silicates, poor in Mg and felsic is poor in silicates and more rich in Mg and Fe

Question 19

Where are igneous rocks found?

Answer 19

Where molten magma is formed beneath the Earth and can travel upwards due to it’s buoyancy

Question 20

What is a clastic sedimentary rock? How is grain size used to name a clastic rock?

Answer 20

Formed by physical processes

Question 21

How does weathering affect the minerals present in clastic sedimentary rock compared to the parent igneous or metamorphic rock?

Answer 21

Less stable minerals like feldspar and mica, break down through chemical weathering into more stable minerals like clay and iron oxides through chemical weathering. Quartz and other minerals have a high resistance to weathering, which results in their increased concentration within the rock

Question 22

How do evaporites and limestones form?

Answer 22

Limestone is formed from the exo-skeletons of marine organisms building up (CaCO3) and evaporites are formed by the evaporation of water from an isolated bay

Question 23

Why has the composition of limestones changed through time?

Answer 23

Most limestone is formed by the activities of living organisms near reefs, but the organisms responsible for reef formation have changed over geologic time.

Question 24

What is diagenesis and lithification?

Answer 24

Diagenesis is the physical, biological and chemical processes that alter sediments after they are intially deposited. Lithification is the processes of forming rock from loose mineral deposits

Question 25

Where are sedimentary rocks found?

Answer 25

Covering 75% of the Earth’s surface, even though they only make up 5% of the Earth’s volume, meaning they’re found at valleys, lakes, deserts, mountain foothills

Question 26

What is metamorphism? How does it cause rocks to change?

Answer 26

The solid-state change of an Igenous rock through intense heat/pressure which causes chemical composition of the rock to change

Question 27

What is a metamorphic grade? How does a mudstone change as metamorphic grade increases?

Answer 27

Metamorphic grade refers to the intensity of heat and pressure conditions that a rock has experienced during metamorphism. Low grade forms slate, medium forms Phyllite, high forms schist and very high forms gneiss

Question 28

Where does metamorphism take place?

Answer 28

Convergent plate boundaries, subduction zones, near magma and fault zones