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MINERALS AND ROCKSAN INTRODUCTION TO GEOLOGY:
MINERALOGY AND PETROLOGY
MineralsA mineral is a naturally occurring solid with a
specific chemical composition and atomic arrangement (crystalline structure).*
Quartz = Silica + Oxygen or SiO2
* Some references also add “inorganic” to the definition, but there are some rare organic minerals too (i.e., whewillite).
Methods to Identify Minerals1. Color2. Streak3. Luster4. Fluorescence5. Chemical Composition6. Hardness
1. Talc2. Gypsum3. Calcite4. Fluorite5. Apatite6. Orthoclase7. Quartz8. Topaz9. Corundum10. Diamond( Mnemonic Devise - The Geologist Can Find An Ordinary Quartz Tourists Call Diamond)
7. Specific Gravity8. Crystal Form9. Optical Properties10. Cleavage11. Fracture12. Magnetism13. Electrical Properties14. Melting Point15. Geologic Setting
Copper
Gold
Pyrite (Fool’s Gold)
Arsenic
Bauxite (aluminum ore)
Kaolin Mine Near Thomson, Georgia
Barite (rose morphology)
Quartz
ROCKS• A rock is any naturally occurring solid mass of mineral or minerals.
• There are three primary types of rocks:1) Sedimentary2) Igneous3) Metamorphic
SEDIMENTARY ROCKS
Rocks formed from accumulation and hardening of water or airborne sediment, plant or animal remains, chemical action, or evaporation.
Some of the most common sedimentary rocks are:• Limestone• Shale• Sandstone
Limestone
Limestone with fossils
Shale
Sandstone
Peat Coal
Igneous Rocks
• Igneous rocks are formed by the cooling of magma from deep within the earth
• There are two main categories of igneous rocks:
1) Intrusive – formed underground
2) Extrusive – formed above ground
The most common intrusive igneous rock is granite.
Some common extrusive igneous rocks include:
• Basalt• Obsidian• Pumice
Granite with thin-section
← Obsidian
Pumice →
Basalt – vesicular (with holes), dense, and thin-section
Metamorphic Rocks
These rocks are formed by other rocks being buried deep within the earth and subjected to very high temperature and pressure.
Common metamorphic rocks include:• Marble• Greenstone• Slate• Schist• Gneiss
Marble with thin section
Greenstone
↑Slate (plain)
Slate with Pyrite ↓
Gneiss
Schist – highly folded
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