Earth Systems and Minerals Overview

Earth as an Operational System

• Earth is an interconnected system of interacting spheres: Geosphere (solid Earth), Atmosphere, Hydrosphere, Cryosphere, and Biosphere.
• Earth materials include minerals, rocks, soil, loose fragments, fossil fuels, and water in various forms (solid, liquid, gas), and atmospheric gases.
• The lithosphere is the rigid outer layer of the geosphere; includes crust and upper mantle, comprising tectonic plates.

Defining a Mineral

• Geological definition of "mineral" differs from nutritional/pharmaceutical use.
• A geological mineral is: naturally occurring, inorganic, solid at room temperature, with an orderly internal crystalline structure, and a definable chemical composition.
• Some naturally occurring substances, e.g., water and mercury, are liquids at room temperature, still considered minerals by exception.
• Calcite, although sometimes formed organically, is considered a mineral due to its abundance and geological significance.
• The International Mineralogical Association amended the definition in 1985: a mineral is an element or compound, normally crystalline, formed by geological processes.
• Mineraloids lack crystalline structure (amber, pearl, opal, obsidian).

Rock Composition

• Rocks are composed of one or more minerals (or mineraloids)
• Three major rock types: igneous (molten material crystallization), sedimentary (mechanical/chemical weathering products), and metamorphic (chemical/physical reorganization under heat/pressure).
• Mineral identification is key to understanding rock formation history.

The Big Ten Minerals

• The International Mineralogical Association recognizes over 5,000 minerals.
• A subset known as "The Big Ten" are critical for identifying common rocks.
• The Big Ten minerals are: olivine, augite, hornblende, biotite, calcium-rich plagioclase, sodium-rich plagioclase, potassium-rich feldspar, muscovite, quartz, and calcite.

Atomic Structure and the Periodic Table

• Matter is composed of atoms with a nucleus (protons, neutrons) and electron cloud.
• Elements are atoms with a specific number of protons (atomic number).
• The periodic table arranges elements by atomic number and chemical properties.
  • Elements have a chemical symbol, name, atomic number, and atomic mass (protons + neutrons).
  • Atomic mass is an average mass reflecting natural isotopes (different neutron counts, same chemical behavior).

Earth's Crust Composition

• Of the 92 naturally occurring elements, eight are dominant in Earth's crust.
• These elements form the most common rock-forming minerals.
• Commonly found elements include oxygen and silicon.

Mineral Chemistry and Bonding

• Minerals form through chemical bonding between elements.
• Ionic bonds form when electrons are transferred between elements, creating charged ions (cations + and anions -).
• Covalent bonds form when electrons are shared between elements to attain full valence shells.
• A unit cell is the smallest repeating unit of a mineral's crystal structure.
• The orderly structure of atoms in a mineral is reflected in the mineral's physical shape.

Silicate Minerals

• The silicate minerals are the largest mineral group.
• The silica tetrahedron (SiO4) is the fundamental building block of silicate minerals.
• The negative charge of the silica tetrahedron is balanced by cations.
• Different silicate minerals form at varying cooling temperatures and magma compositions.

Bowen's Reaction Series

• The Bowen's Reaction Series presents a sequence of mineral formation during magma cooling.
• The discontinuous branch (left side) shows mineral crystallization that changes with decreasing temperature (e.g., olivine, pyroxene, amphibole, biotite).
• The continuous branch (right side) shows plagioclase feldspar crystallization with a continuous change in composition from calcium-rich to sodium-rich with decreasing temperature.

Other Important Mineral Groups

• Calcite is a non-silicate carbonate mineral, often formed organically or by precipitation.
• Clay minerals are sheet silicates formed through weathering.
• Other non-Silicate minerals, and oxides are major components of earth's crust and significant in historical geology.

Additional Mineral Formation Processes

• Minerals can form through organic processes (e.g., shells), weathering, metamorphism, or crystallization of magma.
• Metamorphism occurs deep within the Earth, changing mineral composition and structure.

Applications in Historical Geology

• Mineral identification allows geologists to understand past environments (volcanoes, burial of ancient beaches).
• Isotopes are useful geological tools to understanding Earth's history by analysis of rock samples.
• Oxygen levels and dissolved iron in ancient oceans are significant in Earth history.
• Evaporating water creates halide mineral deposits.