Minerals/EPCC/LM2

1

Minerals

What is a mineral?

►The building block of rocks

Naturally occurring (versus synthetic) Inorganic (no C-H bonds) Crystalline solid (ordered internal

structure) Has a definite but not fixed chemical

composition

02CO, p.20

Fig. 2.3b, p.24

Chemical composition of minerals

►Elements fundmental component of matter Cannot be broken down by ordinary

means

►88 naturally occurring elements in Earth’s crust

Chemical composition of minerals

►8 elements make up 98% of Earth’s crust Oxygen Silicon Aluminum Iron Calcium Magnesium Potasium Sodium

Chemical composition of minerals

►A few elements ARE minerals (eg: gold)

►Most are comprised of 2 to 5 elements Held together by + / - electrical charges 88 elements form over 3,500 minerals 9 rock-forming mineral groups

Chemical Composition Mineral Formulas

►Quartz – SiO2 Silicon and Oxygen

►Calcite – CaCO3 (Calcium and Carbon and Oxygen)

►Olivine – (Fe,Mg)2SiO3 (Iron, Magnesium, Silicon and Oxygen)

►Potassium Feldspar – KAlSi3O8

(Potassium, Aluminum, Silicon, and Oxygen)

Table 2.1, p.24

Crystals

Crystals

►Crystal – any substance whose atoms are arranged in a periodic, repeating pattern This pattern is a crystalline structure Unit cell – the smallest group of atoms

making up the unique pattern

Fig. 2.4, p.25

Crystals

►Crystal face – flat surface occurring when a crystal grows freely Reflects light

Smaller than the mineral

Atomic size

Focus On

►Atom Nucleus

►Neutron►Proton

Electrons

►Chemical bonds Ionic Covalent

Atoms

►The nucleus of the atom contains protons and neutrons with electrons surrounding the nucleus.

Atomic Particles

►Proton – positive charge►Electrons – negative charge►Neutrons – neutral charge►Atomic number = the number of

protons in the element►Atomic mass = the number of protons

+ the number of neutrons

Chemical Formulas – Make up of a Mineral

How do I make elements stick to one another?

Bonding

►A link between atoms ( by virtue of the electrons)

►Na (by itself is a metal) plus Cl (by itself is a poisonous gas)

►But bonded together it makes NaCl – table salt

► This is Ionic Bonding – one electron is transferred to the another

NaCl Bonding

Bonding

►Carbon Dioxide – CO2

►The atomic bonding is :

Covalent Bonding

Physical Properties

How can I identify a mineral?

2.4 Physical properties of minerals

►Crystal habit the way crystals aggregate

Prismatic quartz crystals and massive quartz with no crystal shape

Physical Properties

►Cleavage Some minerals tend to break along flat

surfaces due to weak internal bonding►Fracture

The way a mineral breaks other than cleavage

Physical Properties - Cleavage

►One plane – sheets layered together►Two planes at right angles – stair

stepping►Two planes not at right angles – roof

top►Three planes at right angles►Three planes not at right angles

Physical Properties

►Hardness – Moh’s scale 1 to 10, based on minerals

►Specific gravity Density relative to water

►Color Obvious, but limited use

Table 2.2, p.31

2.4 Physical properties of minerals

►Streak Color of fine powder

►Luster The manner it reflects light

►“Other” properties – smell, taste, magnetism, striations, and reaction to HCl

Mica has a single perfect cleavage plane.

Two planes of cleavage

Three planes of cleavage

Four planes of cleavage

Fracture – no cleavage

Metallic luster of pyrite

How Do we Classify Minerals?

Based on the mineral assemblages

Mineral classes and rock-forming minerals

►Silicates

►Carbonates

►Sulfides

►Sulfates

►Native elements

►Halides

►Oxides

►Hydroxides

►Phosphates

Table 2.3a, p.32

Table 2.3b, p.32

Mineral classes

►Silicates Most abundant rock-forming minerals Over 90% of the Earth’s crust contains

silicate minerals Basic building block for all silicate

minerals – silica tetrahedra Five groups (Si:O ratio, crystal form)

Fig. 2.13b, p.33

Fig. 2.13a, p.33

Fig. 2.14, p.34

Mineral Classes

►Carbonates Forms many sedimentary rocks (CO3)

Limestone CaCO3

Photos of common rock forming minerals

Fig. 2.15a, p.35

Fig. 2.15b, p.35

Fig. 2.15c, p.35

Fig. 2.15d, p.35

Fig. 2.15e, p.35

Fig. 2.15f, p.35

Fig. 2.15i, p.35

Some Common Rocks

2.6 Commercially important minerals

►Ore minerals Metals or other elements profitably

recoverableExamples – native gold and silver, copper ,

lead, zinc►Industrial minerals

Non-metals like halite (salt, phosphates, etc) gypsum (sheetrock), sulfur, apatite

►Gems Prized for beauty & rarity, some industrial

Fig. 2.18, p.36

Fig. 2.17, p.36

Fig. 2.19, p.36