Earth Materials
• Rock = aggregate of one or more minerals.

• Minerals = the building blocks of Rocks.

- properties

- clues concerning processes

- resources, etc.

What is a mineral ?

Definition:

• naturally occurring

• inorganic solid

• definite chemical composition

• regular repeating geometry = crystalline

Mineral Growth
• Minerals grow as they crystallize from solutions (molten rock, hot water, cold water, etc.)

•  atoms of specific elements added to mineral in regular & repeated patterns

Chemical Composition
• building blocks of minerals

• A.  Elements, Atoms, and Ions

­ 1.  Element => simplest chemical; can not be broken down by ordinary means....

• -> 8 make up 98% of the crust

­ (O, Si, Al, Fe, Ca, Mg, K, Na)

Atoms
• structure of an atom

• Nucleus => protons (+) and neutrons (0)

• Orbitals => electrons (-)

• Atomic Number & Atomic Weight

 Ions
• Ions => atoms with extra or too few electrons
- has net charge

- lose extra e- = cation(+)
- gain extra e- = anion (-)

Compounds and Chemical Bonding
• compound = chemical combination of two or more elements held together by bonds.........

• => Minerals = compounds

• Types - a) ionic, b) covalent, c) metallic
Crystalline Structure
• Crystals => atoms arranged in regular, ordered, and repeated patterns.....

Ex.: NaCl Halite

• Rows and columns… Most efficient arrangement of elements.

• Only certain shapes (crystals) possible from this arrangement.
 

Crystal Shape
• Depends on orderly arrangement of atoms

• Diagnostic of individual minerals
­ Crystal faces - angle
­ X-ray diffraction

Earth Materials => Minerals
Properties, Identification, & Types

Mineral Properties (diagnostic)

 having a definite chemical composition and crystalline structure => every mineral has distinct sets of properties => these sets of properties allow for Identification

 Also predicts behaviour in nature

 Chemical Composition
 Crystal Habit

Mineral Properties
 How the mineral breaks

 Cleavage
-orderly breakage

  Fracture

Mineral Properties (continued)
• Hardness
 
• Mohs Hardness Scale
• comparative

• Specific Gravity
• density

Mineral Properties (continued)

 Color  => trace elements

 
 Streak
 

 Luster

Other Mineral Properties
 reaction to acid, taste, magnetism, striations, etc

Mineral Types - Rock Forming Minerals
 Silicates = Most Common

 Why? = ~ 93% of Earth's crust = Si and O
Silicate Structural Unit
 Silica Tetrahedron

 1 silicon and 4 oxygens
Silicate structural groups
• 5 - groups of Silicates based on how tetrahedra share O's
• Independent (island) = no O's shared    Si:O=1:4
 
   => Olivine & Garnet

Silicate structural groups
• Single Chain = 2 O's shared       Si:O=1:3
 => Pyroxenes

• Double Chain = 2 O's shared + 1   Si:O= 4:11
 => Amphiboles

Silicate structural groups
• Sheet = 3 lower O's shared  Si:O= 2:5
­ Clays & mica

Silicate structural groups
  3-D framework all O's shared  Si:O=1:2
 Quartz & Feldspar

Silicate Chemical Groups - 2
 2 Major Silicate Categories => Fe, Mg versus Si
  Mafic Silicates

- high Fe & Mg = low Si    ex.: olivine, pyroxene, amphibole

  => high Temperature, less complex

Silicate Chemical Groups
  Felsic Silicates

 low Mg & Fe = high Si    ex.: mica, feldspar, quartz

  => low Temperature, more complex

Rock-Forming Minerals - Nonsilicates
- Chemical precipitates from water at normal T's

  carbonates => calcite and dolomite

  sulfates => gypsum         evaporites
  halides => halite

Rock-Forming Minerals - Nonsilicates
  Hydrothermal minerals (other than silicates)
­  native elements (gold, silver,copper)
­  sulfides => pyrite & galena
 

  Weathering products
­ oxides => hematite
­ clays