Image from the Mineral and Gemstone Kingdome
Image from the Mineral and Gemstone Kingdome
The Rock Cycle --New rocks are constantly being formed. Igneous rocks cool from melts, they are broken and dissolved at the earth's surface to make sedimentary rocks and are squeezed and altered deep beneath the earth to form metamorphic rocks. Plate tectonics controls which rocks form at what location.
Differentiation -- the earth divided into layers, the solid inner core, the liquid outer core, the mantle, and the crust.
The continents evolved through the gradual accumulation of the lightest material in the earth. As the upper mantle was repeatedly melted and refrozen. The continents continue to grow today.
Self Test: Thicknesses
Crust -- 0 to _____ km deep, Mantle -- _______ to _______ km deep
Outer core _______ to _______ km, Inner Core _______ to _______ km deep
The core is about _____? times thinner than the earth's crust.
Plate Tectonics -- The outer skin of the earth is composed of a hard lithosphere riding on a softer asthenosphere. The lithosphere is broken into a series of plates that move across the earth's surface. The plates separate at divergent margins, where new oceanic crust is made through sea floor spreading, come together at convergent margins, where: 1) one plate is subducted beneath the other at deep sea trenches, or 2) continent-continent collisions. The plates slide past each other at transform margins.
Minerals -- The earth is made up of liquids, gasses and rocks. Most (but not all) rocks are made of minerals.
Definition of a mineral:
A rock -- is a solid aggregate or mass of minerals
Atomic Structure -- Crystals are atoms arranged in a definite, regularly repeating pattern
Chemical Composition - specific ratio of chemical elements
Elements
Atoms
Components
Characteristics
Variations
Atoms are the fundamental building blocks of all chemicals, each atom has a nucleus central core of the atom which contains all of the mass/weight of the atom - composed of neutrons and protons , surrounded by an electron cloud made of electrons - no mass/weight -negative charge -form in shells which can hold a specific number of electrons- interior shells fill before electrons are added to outer shells - atom is most stable when outer shell is full. The number of protons in an atom is its atomic number, that determines its chemical properties. Its atomic mass number is determined by the number of protons and neutrons.
A Sodium atom has 11 protons, and 12 neutrons, so its atomic weight is 23. The atoms of many chemical elements also have isotopes and where some atoms have additional neutrons.
Ions are atoms that are charged because they have either gained or lost electrons. Cations have lost electrons and are positively charged. Common cations are Sodium (Na+), Calcium (Ca2+), Potassium (K+), Magnesium (Mg2+), and Iron (Fe2+ or 3+). Anions are atoms that have gained electrons and are negatively charged. Sometimes anions are formed by groups of atoms that stay together. Common anions are Oxygen (O2-), Sulfur (S2-), Chlorine (Cl-), Carbonate (CO32-), and Sulphate (SO42-).
Crystal structure - regular repeating atomic arrangement
bonds:
Isotopes and Radioactive Decay
Most minerals are crystals with atoms fixed into place by ionic bonding , where the positive and negative charges on the cations and anions attract each other. The positive and negative charges must balance each other, so for example, a CO32- needs two Na+, but only one Ca2+. CaCO3 makes one common mineral called calcite.
Covalent bonds are made when atoms share electrons, without really giving them up. Silicon usually shares an electron with each of 4 surrounding atoms of oxygen, making a silicate anion SIO44-. Almost all the rocks in the earth's crust and upper mantle are silicates.
Structure of Minerals
Polymorphs
Physical properties -- to identify minerals, we must be able to tell them apart through identification of their physical properties.
Common elements in rocks:
Si, Al, O, Ca, Mg, Fe, Na, K
Mineral Classification -- Minerals are classified based on their anions. Oxides have metals attached to O2-, Sulfides are metals with S2-, Carbonates are metals with CO32-. Silicates are metals with networks of SiO44- tetrahedra.
Common Minerals -- Rock-forming, silicate minerals, these minerals are silicates combine to form the rocks in the earth's crust.
silicate structure - SiO4 tetrahedron
Silicate tetrahedra can occur isolated and surrounded by iron and magnesium.
silicate minerals
Olivine is an example and is common in the upper mantle.
Chain Silicates have silicate tetrahedra joined into chains. Amphibole and Pyroxene are examples. These have 2 cleavages and are common in igneous rocks.
Sheet silicates have layers of silicon tetrahedra, they all have one cleavage plane. Muscovite, Biotite, and Kaolinite are examples, Muscovite and Biotite are micas and are common in igneous and metamorphic rocks. Kaolinite is a clay , and forms at the earths surface, it is common in sedimentary rocks. Talc and serpentine form in metamorphic rocks
Framework silicates have silicon tetrahedra joined in three dimensions Quartz,, K-feldspar, Plagioclase (Ca-Na Feldspar ),are examples.
Non-silicate minerals
Self Test
What does Ferromagnesian mean?
Which minerals are the Ferromagnesian Silicates?
Which are the nonferromagnesian silicates?
You should know that calcite and dolomite are important carbonate rock forming minerals, common in sedimentary rocks.
Gypsum and Anhydrite are important sulphates.
You should know the following minerals are important ores
Pyrite and Galena are sulfides.
Magnetite, Hematite, Limonite, are oxides and are ores of iron.
Halite is a source of Rock Salt
Graphite, diamond and sulfur are native elements where the element occurs in its pure form and is not combined with an anion like oxygen or silicate.
Be able to define all the terms on P. 61.