Minerals

Question 1

What methods can we use to test minerals to determine what it is?

Answer 1

Hardness
Streak
Lustre
Cleavage
Colour
Relative Density
Other unique features

Question 2

What is hardness?

Answer 2

The mineral’s ability to resist scratching or abrasion

Question 3

What do we use to measure hardness?

Answer 3

Moh’s scale of hardness

Question 4

What levels of hardness are ascertained using
a) fingernail
b) copper coin
c) steel pin

Answer 4

a) 2.5
b) 3.5
c) 6.5

Question 5

What is streak?

Answer 5

The colour of the mineral in powder form

Question 6

What can we use to determine streak?

Answer 6

a streak plate

Question 7

What is colour?

Answer 7

What colour the mineral is

Question 8

What is lustre?

Answer 8

The way in which a mineral reflects the light

Question 9

Which minerals are easy to identify by colour?

Answer 9

Olivine - green
Pyrite - gold
Chalcopyrite - bronze/yellow with peacock tarnish
Galena - grey

Question 10

What types of lustre are there?

Answer 10

Vitreous
Pearly
Silky
Metallic

Question 11

Give some ‘other’ properties that are unique or rare to some minerals

Answer 11

CRYSTALS:
- quartz = square and pointy
- fluorite = cubic

EFFERVESCENCE:
- calcite = 0.5M HCl

TARNISH
- chalcopyrite - peacock colours

Question 12

What crystal shape is quartz?

Answer 12

hexagonal prism terminated by a pyramid

Question 13

What crystal shape is garnet?

Answer 13

football shaped ish, rhomb shaped faces

Question 14

What crystal shape is calcite?

Answer 14

rhombic shaped

Question 15

What crystal shape is flourite?

Answer 15

cubic or octahedral crystals

Question 16

What crystal shape is galena?

Answer 16

Cubic

Question 17

What crystal shape is gypsum?

Answer 17

fibrous/twinned

Question 18

What crystal shape is haematite?

Answer 18

kidney shaped masses like aero

Question 19

What crystal shape is barite?

Answer 19

bladed crystals (flat like a blade), sometimes form cockscomb masses/desert rose

Question 20

What crystal shape is chiastolite/andalusite?

Answer 20

needle crystals with square cross section, black centre, acicular (needle shaped)

Question 21

What is cleavage?

Answer 21

The tendency of some minerals to break along lines of weakness

• produces flat shiny faces
• if it has no cleavage, it is hard to break, it will fracture unevenly

Question 22

What is fracture?
Give an example

Answer 22

How a mineral with no cleavage breaks (unevenly)

e.g. quartz has conchoidal fracture, it breaks with curved faces

Question 23

What is the difference between hornblende and augite?

Answer 23

HORNBLENDE:
- cleavage planes at 60+120 degrees to each other
- normally hexagonalish
- shiny and splintery looking

AUGITE:
- cleavage planes at 90 degrees to each other
- mediocre cleavage
- normally squareish
- little, well formed crystals
- very dark green (nearly black)
- blocky shape

Question 24

What is the difference between orthoclase and plagioclase feldspars?

Answer 24

ORTHOCLASE: pink/flesh coloured
PLAGIOCLASE: white, multiple twins are black/white under a microscope

BOTH ARE OPAQUE

Question 25

What is twinning?

Answer 25

where two or more crystals of the same mineral grow in a symmetrical relationship with each other - the intergrowth of two or more crystal segments e.g. reflection/rotation

Question 26

What is the element composition of the Earth and its percentages?

Answer 26

Oxygen 47% Silicon 28% Iron 8.1% Aluminium 5% Calcium 3.6% Sodium 2.8% Potassium 2.6% Magnesium 2.1% Other 0.8%

Question 27

What is a silicate tetrahedra?

Answer 27

a very strong and stable combination that easily links up together in minerals, sharing oxygens at their corners - 3 ways to draw - silicates the most common minerals in the crust and mantle (95% crust, 97% mantle) e.g. SiO2 = quartz (Mg/Fe)2SiO4 = olivine

Question 28

What is a mineral?

Answer 28

inorganic, naturally forming crystalline substances that are the ingredients that make up rocks

Question 29

What two categories can we divide rocks into

Answer 29

Crystalline Clastic

Question 30

What does crystalline mean? What types of rocks are crystalline?

Answer 30

the grains are interlocking - they have CRYSTALS IGNEOUS/METAMORPHIC

Question 31

What does clastic mean? What type of rocks are clastic?

Answer 31

the grains are not interlocking - they have CLASTS SEDIMENTARY

Question 32

What does texture mean? What does it incorporate?

Answer 32

the grains and their relation to each other - texture - shape - size - relative size (all same/different)

Question 33

What is the Goldschmidt Classification?

Answer 33

the classification of the chemical into groups according to the part of the Earth where they tend to concentrate

Question 34

What are the classes in the Goldschmidt Classification?

Answer 34

Lithophile Siderophile Atmophile Chalcophile

Question 35

What does lithophile mean? What are the features of lithophiles?

Answer 35

rock loving - combines readily with oxygen - relatively low density - concentrated in crust

Question 36

What does siderophile mean? What are the features of siderophile?

Answer 36

iron loving - high density - tends to sink into the core/rare in the crust - practically no affinity for oxygen - tends to be precious metals

Question 37

What does atmophile mean? What are the features of atmophile?

Answer 37

gas loving - mostly on or above the surface - liquids or gases, including noble gases - H (H2O), C (CO2, CO, CH3...) and N

Question 38

What does chalcophile mean? What are the features of chalcoophiles?

Answer 38

ore loving - combines readily with sulfur, silicon and other chalcogens (group 16 periodic table) (apart from oxygen) - not common - forms the bulk of commercially important metals