Atoms, Compounds,Atoms, Compounds,Minerals and RocksMinerals and Rocks

Atoms

Atoms - the smallest unit of an element that retains the physical and chemical properties of that element

Made up of a nucleus, and a “cloud” of electrons

Nucleus made up of protons and neutrons

Number of protons determines which type of Element the atom is

Element - distinctive type of matter with specific phyisical and chemical properties

Examples: Iron, Oxygen, Hydrogen, etc.

Generally grouped as Metals or Nonmetals

Compounds

Compound - substances made by the bonding of chemical elements (from chemical reactions). Compounds are comprised of two or more different elements.

Chemical bonds may be made by

– sharing electrons between atoms - covalent bonds

– lending or borrowing electrons with mutual attraction of oppositely charged atoms - ionic bonds

The properties of compounds are dramatically different from those of the elements that comprise them

A Mineral isA Mineral is

Naturally occurringNaturally occurring Inorganic (not made from animals or Inorganic (not made from animals or

plants)plants) SolidSolid with a definite chemical composition with a definite chemical composition

(formula)(formula) and an orderly arrangement of atoms and an orderly arrangement of atoms

(crystal structure)(crystal structure) Minerals are chemical compounds

Crystal StructureCrystal Structure

How do crystals form?How do crystals form?

Atoms must be free to Atoms must be free to movemove

Chemical bonds dictate Chemical bonds dictate the geometric arrangement the geometric arrangement of atomsof atoms

Crystal is external Crystal is external manifestation of order at manifestation of order at atomic levelatomic level

Crystal StructureCrystal Structure

Atoms must be free to Atoms must be free to movemove

Under what conditions Under what conditions does this occur?does this occur?

In a melt (magma)In a melt (magma)

In solution (dissolved in In solution (dissolved in water)water)

Abundance of chemical elements Abundance of chemical elements in Earth’s Crustin Earth’s Crust

O – 46.6%O – 46.6% Si – 27.7%Si – 27.7% Al – 8.1%Al – 8.1% Fe – 5.0%Fe – 5.0% Ca – 3.6%Ca – 3.6% Na – 2.8%Na – 2.8% K – 2.6%K – 2.6% Mg – 2.1%Mg – 2.1% Other – 1.7%Other – 1.7%

Silicate MineralsSilicate Minerals

O and Si make up nearly 75% of crustO and Si make up nearly 75% of crust Most common elements should make up Most common elements should make up

most common mineralsmost common minerals Common “rock-forming” minerals are Common “rock-forming” minerals are

silicatessilicates Silicates have Si, O and other elements such Silicates have Si, O and other elements such

as Fe, Mg, Al, Na, K, Caas Fe, Mg, Al, Na, K, Ca

Silicon-Oxygen TetrahedronSilicon-Oxygen Tetrahedron

““Building Block” of Silicate mineralsBuilding Block” of Silicate minerals Si surrounded by 4 OSi surrounded by 4 O O may be shared so that tetrahedra link togetherO may be shared so that tetrahedra link together

Sharing TetrahedraSharing Tetrahedra

Olivine – Fe,Mg silicateOlivine – Fe,Mg silicateSingle TetrahedraSingle Tetrahedra

Pyroxene – Fe, Mg, Al silicatePyroxene – Fe, Mg, Al silicateSingle ChainsSingle Chains

Amphibole – Fe, Mg, Ca, Na, Al, F Amphibole – Fe, Mg, Ca, Na, Al, F silicatesilicate

Micas (biotite, muscovite) – K, Al Micas (biotite, muscovite) – K, Al +/-Ca, Mg, Fe silicates+/-Ca, Mg, Fe silicates

Complex silicatesComplex silicates

Quartz SiOQuartz SiO22

Feldspars Feldspars – Na,Ca silicates Na,Ca silicates

PlagioclasePlagioclase

– K, Al silicatesK, Al silicates

Other mineralsOther minerals

Bowen’s Reaction SeriesBowen’s Reaction Series

Other Mineral “Families”Other Mineral “Families”

Halides – contain metals and Cl, F, I, etc.Halides – contain metals and Cl, F, I, etc. Carbonates – contain metals and COCarbonates – contain metals and CO33

Oxides/Hydroxides – contain metals and O Oxides/Hydroxides – contain metals and O or OHor OH

Sulfides – contain metals and SSulfides – contain metals and S Phosphates – contain metals and POPhosphates – contain metals and PO44

““Native” Elements – pure elementsNative” Elements – pure elements

So, What is a Rock?So, What is a Rock? A Rock is: An “aggregate” of minerals Usually, a mixture of two or more minerals, each

of which remains distinct