Atoms, Ions, and Elements -
Mineral Building Blocks

Earth Materials

Rock = aggregate of one or
 more minerals.

Minerals = the building
 blocks of Rocks.

- properties

- clues concerning processes

- resources, etc.

Chemical Composition
=> building blocks of minerals

.  Elements, Atoms, and Ions

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

distinctive properties

100 commonly occurring, 88 elements in Earth's crust

-> 8 of these make up 98% of the crust
(O, Si, Al, Fe, Ca, Mg, K, Na)

2. Atoms
structure of an atom

Nucleus => protons (+) and neutrons (0)
 Orbitals => electrons (-)

=> atomic number and atomic weight

3.  Ions => atoms with extra or too few electrons
 has net charge

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

Why do ions form?
 chemical stability
octet rule

B.  Compounds and Chemical Bonding

 compound = chemical combination of two or more
  elements held together by bonds.........

Types of Chemical Bonds

1.  Ionic => electrical attraction between cations (+) and anions (-)
  ex.  Na+ + Cl- = NaCl Halite

2.  Covalent => e- shared among neighboring atoms to fill orbitals
 Very strong bond.......

II.  What is a mineral ?

A.  Definition:

 naturally occurring

 inorganic solid

 definite chemical composition

 regular repeating geometry = crystalline
Crystalline Structure
 B.  Crystals => atoms arranged in regular, ordered,  and repeated patterns.....

 Ex.: NaCl Halite

1.  Rows and columns of alternating Na+ and Cl- intersecting at right angles. Most efficient arrangement of elements.

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

III.  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

1.  Chemical Composition
2.  Crystal Habit
3.  Cleavage
-orderly breakage
4.  Fracture
5.  Hardness
 Mohs Hardness Scale
Comparative
6.  Specific Gravity
- density
7.  Color  => trace elements
8. Streak
9.  Luster
Other => reaction to acid, taste, magnetic, striations, etc.

IV.Mineral Types

 A. Silicates = Most Common

~ 93% of Earth's crust = Si and O

B.  Silicate Structural Unit

 1.  Si surrounded by 4 O's = silica tetrahedron

 2.  Si - O tetrahedrons link by sharing O's

(SiO4)4- = anion with net charge -4 -> attaches to cation

D.  2 Major Silicate Categories => Fe, Mg versus Si

1.  Ferromagnesian Silicates (mafic) - dark colors

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

  => high Temperature, less complex

2.  Nonferromagnesian Silicates (felsic) - light colors

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

low Temperature, more complex

E.  Nonsilicates =>
 1.  Chemical precipitates from water at normal T's

 -carbonates => CaCO3 (calcite) &  (Ca,Mg)CO3 (dolomite)

 -sulfates => CaSO4 (gypsum)         evaporites
 -halides => NaCl (halite)

2.  Hydrothermal minerals (other than silicates)

 - native elements (Au, Ag, Cu)

 - sulfides => FeS2 (pyrite)

3.  Weathering products

 - oxides => Fe2O3 (hematite)