Introduction to minerals

Question 1

Definition of a MINERAL

Answer 1

A natural occurring inorganic solid, crystalline substance which has a fixed structure and a chemical composition which can be fixed or varied

Question 2

MINERALOID

Answer 2

An amorphous solid material without a fixed composition, can be organic and can be man made

Question 3

MINERALS

Answer 3

Crystals- solids that are naturally bounded by flat faces meeting at sharp edges, with a crystal shape(lattice), often referred to as the building blocks of rock - most behave as ionic solids

Question 4

Ionic bonding

Answer 4

The attraction of opposite charges (transferring and accepting of electrons from the valence shell)

Question 5

Covalent bonding

Answer 5

The sharing of electrons in the valence shell

Question 6

Metallic bonding

Answer 6

The attraction between the delocalized electrons present in the lattice of the metals

Question 7

Ions

Answer 7

Atoms with positive or negative charges due to loss or gain of electrons

Question 8

Anion

Answer 8

An atom that has gained electrons, therefore has a negative charge and has more electrons than protons

Question 9

Cation

Answer 9

An atom that has lost electrons, therefore has a positive charge and has more protons than electrons

Question 10

Unit cell

Answer 10

The smallest arrangement of atoms which may be repeated regularly in 3 dimensions to form a crystal lattice

Question 11

Ionic Radius

Answer 11

The size of atoms within an ionic solid- determines how ions pack together to form minerals

Question 12

Coordination number

Answer 12

The number of anions around each cation in the crystal lattice - controlled by the ionic radii of the cations and anions

Question 13

Radius Ratio

Answer 13

rc/ra - radius of the cation / radius of the anion

Question 14

Igneous environment growth

Answer 14

High temp = >700°C - melting
varied pressure
Minerals are free to grow how they like
Minerals formed in this environment:
   Moderately hard to hard
   Anhydrous and hydrous
   Good crystalline shape if they crystallize early

Question 15

Metamorphic environment growth

Answer 15

Moderate to high temp = 200-700°C - no melting, solid State recrystallisation
Low to high pressure
In some cases abundant water
Minerals form in a confined space hence their shape is
strongly influenced by pressure gradients
Mineral formed in this environment:
Moderately hard to hard
Hydrous and anhydrous
Poor Crystalline shape

Question 16

Geothermal environment growth

Answer 16

Moderate temp = 200 - 500°C
Low pressure
Abundant water and oxygen
Minerals are able to form in free environment - minerals 
   deposited in cavities and fractures
Minerals formed in this environment:
   Soft
   Hydrous
   Often has a good crystalline shape
   Many valuable ores are formed in this environment

Question 17

Weathering environment growth

Answer 17

Low temp and pressure - Earth's surface
Abundant water and oxygen
Minerals are able to form in free environment
Large variety of chemical components 
Minerals formed in this environment:
   Soft
   Hydrous
   Good crystalline shape
Characterized by clays

Question 18

Hardness

Answer 18

Resistance of a mineral to abrasion, reflection of strength of atomic bonds

Question 19

Clevage

Answer 19

Tendency for a mineral to split along a particular plane, occurs along layers of weak bonds in the crystal lattice.

Question 20

Fracture

Answer 20

How a mineral breaks when lacking weak planes in its structure

Question 21

Specific gravity (density)

Answer 21

Mass per unit volume of a mineral

Question 22

Streak

Answer 22

Colour of powdered mineral, often more diagnostic than colour