Rock-Forming Minerals Overview

Rock-Forming Minerals Overview

• Minerals are categorized into families based on their anion composition.

Silicates

• Most abundant mineral group in the Earth's crust.
• Key component: silicate ion (SiO4)4-, typically forms a tetrahedral structure.
• Common silicates include quartz (SiO2), K-feldspar (KAlSi3O8), olivine ((Mg, Fe)2SiO4), and kaolinite (Al2Si2O5(OH)4).
• Silicate tetrahedra can combine in various arrangements to form diverse minerals.

Carbonates

• Composed of cations and carbonate ion (CO3)2-.
• Notable examples include calcite (CaCO3), dolomite (CaMg(CO3)2), and siderite (FeCO3).
• Frequently found in limestone and marble, which are composed largely of calcite.

Oxides

• Formed from metallic cations combined with oxygen.
• Essential for various metal ores such as iron, chromium, and titanium.

Sulfides

• Minerals consisting of metallic cations bonded to sulfide ions (S2-).
• Important sources for copper, zinc, nickel, lead, and iron; notable examples are pyrite (FeS2) and galena (PbS).

Sulfates

• Composed of sulfate ions (SO4)2-.
• Common minerals include gypsum (CaSO4·H2O) and anhydrite (CaSO4).

Physical Properties of Minerals

• Hardness: measured using scratch tests.
• Cleavage: minerals break along flat surfaces based on crystal structure.
• Fracture: irregular breakage not along cleavage planes, such as conchoidal fractures.
• Luster: the way light interacts with a mineral’s surface (e.g., metallic, vitreous).
• Color: generally unreliable for identification; streak color provides more reliable information.
• Specific gravity and crystal habit/shapes vary among minerals.

Identification Techniques

• Chemical composition analysis using microprobes and chemical methods.
• Crystal structure analysis through X-ray diffraction.
• Physical properties assessment.

Special Properties of Minerals

• Certain minerals possess unique traits such as magnetism, fluorescence, and chemical reactivity.

Mineral Resources

• Building materials include stone, sand, gravel, and limestone.
• Non-metallic minerals encompass gypsum, coal, and various industrial minerals.
• Metallic minerals include non-ferrous and ferrous metals such as copper, gold, and iron.

Types of Ore Deposits

• Diverse origins include magmatic, pegmatite, hydrothermal, and sedimentary processes leading to different valuable minerals.

Economic Considerations in Mining

• Factors influencing mining economics include ore richness, quantity, extraction costs, and market prices of the extracted products.

Life Cycle of a Mine

• Phases of mining include exploration, development, active mining (with various processing stages), and eventual shut-down.

Issues and Challenges in Mineral Exploitation

• Questions surrounding mineral ownership and access to resources in unclaimed regions like the sea floor and Antarctica.
• Prospective consequences include environmental impacts such as pollution and mismanagement of natural resources.

Soil as a Resource

• Soil is a thin, crucial layer of the Earth's surface, important for sustaining life.
• Three primary soil types are classified as sand (gritty), silt (smooth), and clay (sticky and malleable).

Rock and Mineral Classification

• Rocks are characterized by visual and textural properties, including color, texture (proportion of sand, silt, clay), and hardness measurement through scratch tests.