Introduction to Minerals and Rocks
Importance of Minerals
- Fundamental building blocks of The Earth
- They hold important clues for the history of The Earth
- Knowledge of Minerals and rocks is the first step to better identifying and managing Earth's resources
- They are important to our health
- They serve various uses for modern economic development
- 'If we didn't grow it, it came from a mineral'
Periodic Table
- 92 Elements found in nature (Hydrogen to Uranium)
- 8 elements make up more than 90% of The Earth's crust. (O, Si, Al, Fe, Ca, Na, K, Mg)
What are Minerals?
- Naturally occurring Earth materials formed by geological processes
- They each have a specific chemical composition
- They are inorganic
- Solids
- Have an orderly, regular, repeating crystalline structure
- Cube (halite, pyrite)
- Hexagon (quartz)
- Octahedron (Diamond Flourite)
- Dodecahedron (garnet)
Rocks
- Rocks are inorganic solids that are made or of groups of minerals
- They can be formed of a single mineral or a combination
There are 3 Kinds of Rocks
- Ingenious Rocks
- Crystallization of Molten Rock
- Sedimentary Rocks
- Accumulation of layers of sediment
- Metamorphic Rocks
- Buried sedimentary rocks that have been altered by heat and pressure
Rock Cycle - A Recycling System
- Deposition - Depositing of small particles in a layer
- Weathering - Effects of wind and water breaking the bonds of the rock
- Erosion - Transportation of the weathered particles to a new location
- Metamorphism - Pressures and temperatures applied
Intrusive Igneous Rocks
- Crystallized from Molten Rock (magma)
- Slower cooling underground
- Larger coarser crystals - can be seen with your eyes alone
- Surrounded by smaller crystals - Phenocrysts
- Surrounding rock that is incorporated - Inclusions
- Batholiths and Plutons
- Large Igneous Intrusions
- Many Plutons make a Batholith
Extrusive Igneous Rocks
- Crystallize at Earth's surface from Molten Rock (lava)
- Cool rapidly so they have fine grains - small crystals that require a microscope to see.
- A mass of extrusive igneous rock surrounding bits of phenocrysts is called a porphyritic rock.
Sedimentary Rocks
- 75% of all rock on the Earth's surface
- Weathering (breaking, alteration, and erosion of rock) results in transportation of sediment via wind, water, or ice. The sediment is then deposited and goes through a process called lithification where it is compacted and cemented or 'glued' together.
- Sedimentary rocks are deposited in layers called
- There are two types of sedimentary rocks, Detrital (or clastic) and Chemical (or non-clastic)
Detrital (Clastic) Sedimentary Rocks
- Classified according to grain size:
- Shale (layered)
- Mudstone: < 1/256mm
- Siltstone: 1/256mm - 1/16mm
- Sandstone: 1/16mm - 2mm
- Conglomerate: > 2mm
Chemical (Non-Clastic) Sedimentary Rocks
- Classified according to mineral composition
- Halite - NaCl
- Gypsum - CaSO4, 2H2O
- Limestone - CaCO3
Metamorphic Rocks
- Form when heat, pressure, and//or chemically active fluids interact with sedimentary or igneous rocks
- There are three kinds of metamorphic rocks defined by process:
- High pressure, low temperature - Regional Metamorphism
- characteristic of subduction zones.
- sediments have heavy load applied to them and produce a more dense rock.
- High pressure, high temperature - Regional Metamorphism
- changes low-grade sedimentary rocks to high-grade metamorphic rocks.
- Low pressure, high temperature - Contact Metamorphism
- Magma intrudes into upper crust and heats up surrounding rocks
- Heat source can provide environment for mineral deposits/valuable ores.
