Unit 3: Earth Materials (35 Hours = 35 classes)

Minerals: Why care? Why should we care? Nearly all manufactured products we use are obtained from minerals. aluminum: soft drink cans graphite (carbon): our pencil lead copper: wire for our electricity talc: baby powder silver & gold: our jewelry silicon: our computer chips

Minerals: Why care? Why else care? Important geologic events that affect us involves rocks and minerals. Why else care? volcanic eruptions earthquakes weathering and erosion mountain building

4. Possess an orderly internal structure Minerals: the building Minerals: blocks of rocks What is a mineral? -> To be considered a mineral, it must: 1. Occur naturally 2. Be inorganic 3. Be a solid 4. Possess an orderly internal structure 5. Have a definite chemical composition

2) contains a mixture of one or more minerals Minerals: the building Minerals: blocks of rocks What is a rock? -> different from that of a mineral. A rock: 1) is solid 2) contains a mixture of one or more minerals 3) occurs naturally as part of our planet

Some rocks composed entirely of one mineral Minerals: the building Minerals: blocks of rocks Rocks and minerals Some rocks composed entirely of one mineral limestone (calcite) Most rocks have more than one kind of mineral granite Some rocks contain non-mineral matter coal (has organic debris) obsidian (volcanic glassy rock -> not crystalline)

Minerals The composition of minerals rock mineral

The composition of minerals Example from book: Figure 2.2 Granite & constituent minerals

minerals rock mineral minerals The composition of minerals So far we have: minerals rock mineral collection of one or more minerals A collection of one or more types of atoms

How do we define Minerals? chemical composition The composition of minerals How do we define Minerals? chemical composition internal (“atomic”) structure (~ 4000 minerals on Earth)

Example: mineral quartz made up of silicon (Si) & oxygen (O) atoms Chapter 2: Matter and minerals 3. The composition of minerals Atomic structure Example: mineral quartz made up of silicon (Si) & oxygen (O) atoms

element: is a pure Chemical substance consisting of one type of atom. Minerals The composition of minerals atom: the smallest particle of a chemical element that retains the chemical properties of that element. element: is a pure Chemical substance consisting of one type of atom.

112 known elements Only 92 occur naturally The composition of minerals

There are over 100 known elements, but Minerals The composition of minerals There are over 100 known elements, but only 8 of these make up more than 98.5% of Earth’s crust by mass; Oxygen (46.6%) 2) Silicon (27.7%) 3) Aluminum (8.1%) 4) Iron (5.0%) 5) Calcium (3.6%) 6) Sodium (2.8%) 7) Potassium (2.6%) 8) Magnesium (2.1%)

Different elements are joined together to create specific minerals. The composition of minerals Different elements are joined together to create specific minerals. Example: Quartz contains silicon (Si) and oxygen (O) element name symbol

An atom is a world unto itself, and has the following parts: Minerals The composition of minerals But what is an atom?? An atom is a world unto itself, and has the following parts: nucleus: heavy central region electrons: negatively charged particles circling nucleus electrons nucleus

protons = positive electrical charge Minerals The composition of minerals protons = positive electrical charge neutrons = neutral electrical charge The electrons are negatively charged neutrons electrons one atom protons

A model of a single atom The composition of minerals Minerals T&L: Figure 2.4 A

...in 3D The composition of minerals Minerals Again, a model of one atom Nucleus of protons and neutrons T&L: Figure 2.4 B

# protons determines type of atom Minerals The composition of minerals # protons determines type of atom # protons determines the atomic number Example: All Helium atoms have 2 protons “ Carbon “ “ 6 “ “ Uranium “ “ 92 “

The composition of minerals Atomic structure Minerals The composition of minerals Periodic table of the elements 6 => 6 protons equals # of protons

Different elements combine to make compounds Minerals The composition of minerals Different elements combine to make compounds Compound- two or more elements combined. Example 1: water (2 hydrogen atoms + 1 oxygen atom = H2O) Example 2: salt (1 sodium atom + 1 chlorine atom = NaCl) The smallest amount of a compound is a molecule.

6 protons = carbon Carbon: The composition of minerals # of protons determines the type of atom 6 protons = carbon # neutrons in an atom can vary # neutrons + # protons = “mass number” 6 protons & 6 neutrons: mass number = 12 C 6 protons & 7 neutrons: mass number = 13 C 6 protons & 8 neutrons: mass number = 14 C How we write it Carbon: 12 13 14

C These variations of the same element are isotopes Minerals The composition of minerals These variations of the same element are isotopes Some isotopes are unstable, and disintegrate through radioactive decay C 14 Example: Carbon-14 is unstable The rate of disintegration is steady, which lets us use this as a clock

How do different atoms combine? Bonding Minerals The composition of minerals Bonding How do different atoms combine? Bonding 3 main types of bonds: “ionic bond” – lose or gain electrons to form ions “covalent bond” - sharing electrons “metallic bond” - electrons are free to move about from atom to atom

Minerals The composition of minerals When atoms give away or gain electrons, they are no longer electrically neutral: they “have a charge” Any atom with a charge is called an “ion” 90% of minerals are ionic

Ionic Bonding Example: Table Salt: Sodium (Na) and Chlorine (Cl) Minerals The composition of minerals Ionic Bonding Example: Table Salt: Sodium (Na) and Chlorine (Cl) Sodium loses an electron to share with Chlorine atom Now, becomes a positively charged ion Chlorine gains the electron from the Sodium atom Now, becomes a negatively charged ion

Example: Sodium (Na) and Chlorine (Cl) Minerals The composition of minerals Example: Sodium (Na) and Chlorine (Cl) Atoms arrange in orderly fashion: w/ alternating sodium and chlorine atoms, so each negative ion is surrounded by positive ions, and visa versa.

Example: Sodium (Na) and Chlorine (Cl) Minerals Example: Sodium (Na) and Chlorine (Cl) Such orderly arrangement at the atomic level produces specific shapes in crystals at the macroscopic level that reflect the atomic structure

Covalent Bonding - electron sharing Like diamond, C Minerals The composition of minerals Covalent Bonding - electron sharing Like diamond, C

Metallic Bonding - free movement of electrons between cations Minerals The composition of minerals Metallic Bonding - free movement of electrons between cations

….but not all compounds are minerals: WHY? The composition of minerals Most minerals are compounds ….but not all compounds are minerals: WHY?

The structure of minerals What determines the particular crystalline structure of a mineral? diamond Amethyst (quartz) pyrite

The structure of minerals size of the ions involved electrical charge of the ions involved

Important: conditions under which a mineral forms: temperature Minerals The structure of minerals Important: conditions under which a mineral forms: temperature pressure Completely different minerals can form from the same atom,depending on how the atoms are arranged more pressure -> closer packing of atoms -> different substance

Different minerals with the same chemical composition The structure of minerals Different minerals with the same chemical composition are “polymorphs” graphite (a form of pure carbon) soft gray material, e.g., pencil lead crystal structure: sheets of carbon diamond (also pure carbon) forms deep in Earth at high pressures, & is hardest substance known to humans crystal structure: dense & compact