Mineralogy Overview

Definition of Minerals

• Minerals are naturally occurring, homogeneous solids.
• They form through geological processes.
• Minerals have a definite chemical composition.
• They have an ordered atomic structure (crystal lattice).
• Minerals have specific physical properties that distinguish them from other substances.
• Minerals are inorganic, meaning they do not contain organic materials.

Mineral Classification

• Mineral classification categorizes minerals based on chemical composition and structure.
• Polymorphs share a common chemical formula but have different crystal structures (e.g., diamond and graphite).
• Mineraloids resemble minerals but lack a definite crystalline structure (e.g., opal and obsidian).

Key Characteristics of Minerals

• Minerals are homogeneous, naturally occurring substances.
• They have a definite chemical composition.
• Their atomic structure is highly ordered.
• They have specific physical properties, including hardness, luster, and cleavage.

Crystalline Structure

• Crystalline structure refers to the arrangement of atoms in a mineral.
• Crystalline solids have a regular, repeating three-dimensional lattice structure.
• Amorphous solids lack this specific order.

Physical Properties of Minerals

• Physical properties help identify and classify minerals.
• Color is useful for initial identification, but can vary.
• Streak is the color of the mineral's powder, which is more consistent.
• Hardness is measured on the Mohs scale.
• Cleavage is the tendency of a mineral to break along smooth planes.
• Fracture describes how a mineral breaks in a non-cleavage manner.
• Luster describes how light reflects off a mineral's surface (e.g., metallic, glassy).
• Specific Gravity is the density of a mineral relative to water.
• Magnetism and Tenacity are other properties used in mineral identification.

Rocks - Formation of Minerals

• Rocks are aggregates of minerals.
• The Rock Cycle describes the processes of transformation between igneous, sedimentary, and metamorphic rocks.

Igneous Rocks

• Igneous rocks form from the cooling of molten rock (magma or lava).
• Intrusive igneous rocks cool slowly beneath the surface.
• Extrusive igneous rocks cool quickly at the surface.

Sedimentary Rocks

• Sedimentary rocks form from the accumulation and cementation of sediments (fragments of other rocks, minerals, or organic matter).
• Chemical sedimentary rocks form from dissolved minerals precipitating out of water.
• Clastic sedimentary rocks form from cemented fragments of other rocks.
• Biochemical sedimentary rocks form from living organisms.

Metamorphic Rocks

• Metamorphic rocks form when existing rocks are transformed by heat, pressure, or chemical reactions.
• Foliated metamorphic rocks possess distinct layering.
• Non-foliated metamorphic rocks lack layering.

Earth Processes

• Earth processes include various geological phenomena and activities that continuously shape Earth's surface.
• Geologic processes continuously shape the Earth's surface.
• Surface evolution changes landforms due to geological activity.
• Earth's magnetic field protects the planet from solar radiation.
• Plate movement causes earthquakes, volcanic activity, and builds mountains.
• River erosion and sediment deposition reshape landforms.

Endogenic Processes

• Endogenic processes occur deep within Earth's interior.
• They are driven by internal heat and involve mountain building, volcanic activity, and earthquakes.
• Tectonic processes involve the movement of Earth's lithospheric plates.
• Igneous processes are the formation and crystallization of magma.

Exogenic Processes

• Exogenic processes occur at or near the Earth's surface and are driven by solar energy.
• Examples include weathering, erosion, and mass movement.
• Weathering breaks down rocks into smaller pieces and sediment.
• Erosion transports rock from one location to another.
• Mass wasting involves the movement of soil and rock down slopes.
• Sedimentation involves the accumulation of sediments.

Weathering

• Weathering is the process of breaking down rocks and minerals at or near the Earth’s surface.
• Types include Physical (mechanical), Chemical, and Biological weathering