Lecture 5 Earth Materials: Minerals and Rocks

About Earth Materials All Earth materials are composed of atoms bound together. Minerals are composed of atoms bonded together and are the building blocks of rocks. Rocks are composed of minerals and they record various geologic processes.

Minerals are the building blocks of rocks. 1. What Are Minerals? Minerals are the building blocks of rocks.

What Are Minerals? Geologists define mineral as a naturally occurring, solid, crystalline substance, usually inorganic, with a specific chemical composition.

Naturally occurring = found in nature What Are Minerals? Naturally occurring = found in nature Solid, crystalline substance = atoms are arranged in orderly patterns Usually inorganic = not a product of living tissue With a specific chemical formula = unique chemical composition

2. The Structure of Matter The atom is the smallest unit of an element that retains the physical and chemical properties of that element.

Atomic nucleus: protons and neutrons. 2. The Structure of Matter Atomic nucleus: protons and neutrons. Electrons: cloud of moving particles surrounding the nucleus. Example: the carbon atom (C)

The Carbon Atom electron cloud atomic nucleus

The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons …

The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons … proton (+) neutron

The Carbon Atom electron cloud atomic nucleus carbon has 6 electrons… … and a nucleus of 6 protons … electron (–) proton (+) neutron

The Carbon Atom electron cloud atomic nucleus Carbon has 6 electrons … … and a nucleus of 6 protons … … and 6 neutrons having no charge. electron (–) proton (+) neutron

2. The Structure of Matter Isotopes – atoms of the same element with equal numbers of protons but different numbers of neutrons.   Example: the carbon atom (C) typically has 6 neutrons and 6 protons (called C12), but there are also small amounts of C13 and C14.

Example: H + H + O = H2O Example: Na + Cl = NaCl 2. The Structure of Matter Chemical reactions – interactions of the atoms of two or more elements in certain fixed proportions. Example: H + H + O = H2O Example: Na + Cl = NaCl

Chemical compounds that are minerals form by: electron sharing or 2. The Structure of Matter Chemical compounds that are minerals form by: electron sharing or electron transfer

Carbon atoms in a diamond Electron Sharing: Carbon atoms in a diamond

Sodium (Na) + chlorine (Cl) = Electron Transfer: Sodium (Na) + chlorine (Cl) = NaCl (halite)

Sodium (Na) + chlorine (Cl) = Electron Transfer: Sodium (Na) + chlorine (Cl) = NaCl (halite) Each sodium ion (circled in red) is surrounded by 6 chloride ions (circled in yellow), and vice versa.

in the proper proportion and proper arrangement 3. The Formation of Minerals How do minerals form? Crystallization – atoms come together in the proper proportion and proper arrangement

Electrical charges of atomic ions Cation – positively charged 3. The Formation of Minerals Electrical charges of atomic ions Cation – positively charged Anion – negatively charged Atomic ions arrange themselves according to charge and size.

3. The Formation of Minerals The forces of electrical attraction between protons (+) and electrons (-) that hold minerals and other chemical compounds together covalent bonds ionic bonds metallic bonds

3. The Formation of Minerals

During cooling of molten rock During evaporation of water 3. The Formation of Minerals When do minerals form? During cooling of molten rock During evaporation of water Upon changes in temperature and pressure on existing minerals

Chemical classes of minerals: 4. Classes of Rock-Forming Minerals Chemical classes of minerals: Silicates – contain O and Si Carbonates – contain C and O Oxides – contain O and metallic cations Sulfides – contain S and metallic cations Sulfates – contain SO4 and metallic cations

Chemical classes (cont.): Halides – contain Cl, F, I, or Br 4. Classes of Rock-Forming Minerals Chemical classes (cont.): Halides – contain Cl, F, I, or Br Hydroxides – contain OH Native elements – masses of all the same element metallically bonded

4. Classes of Rock-Forming Minerals Formation of silicate minerals Silicate ion (SiO44–) Oxygen and Silicon are the two most abundant elements in Earth crust Silicates are the most common mineral in the Earth’s crust Oxygen ions (O2–) Silicon ion (Si4+)

Identity is determined by: texture composition 6. What Are Rocks? Rocks are naturally occurring solid aggregates of minerals, or in some cases, non-mineral solid matter. Identity is determined by: texture composition

Rocks are classified into three groups: 6. What Are Rocks? Rocks are classified into three groups: Igneous Sedimentary Metamorphic

6. What Are Rocks? [granite and gneiss: John Grotzinger/Ramón Rivera-Moret/Harvard Mineralogical Museum; sandstone: John Grotzinger/Ramón Rivera-Moret/MIT.] Production of igneous and metamorphic rocks typically requires proximity to a plate boundary

Igneous Rocks

Sedimentary Rocks

Metamorphic Rocks Recrystallization of existing rocks leads to the formation of metamorphic rocks

Interactions between the plate tectonic and climate systems 7. The Rock Cycle Interactions between the plate tectonic and climate systems

7. The Rock Cycle

7. The Rock Cycle

7. The Rock Cycle

7. The Rock Cycle

7. The Rock Cycle

7. The Rock Cycle