GEO 208 Environmental Geology: Mineral Resources and the Environment Study of the Natural Environment

Course Overview and Learning Objectives

• Course and Textbook Reference: GEO 208 Environmental Geology. Earth Resources and Environmental Textbook: Chapter 2 (Pages 28-29, 38-50) and Chapter 14 (Pages 403-429).
• Main Topic: Week II - Mineral Resource and Environment.
• Thematic Focus: The materials cover minerals (definitions, formations, examples, uses, and hazards), rocks (formation, classification, resource use, and the rock cycle), and the environmental and economic significance of mineral types.
• Key Educational Goals:     * Define minerals and explain their formation via geological, biological, and weathering processes.     * Identify important mineral and rock types and their ecological significance.     * Differentiate between a RESOURCE and a RESERVE, emphasizing the geological, economic, and legal factors that define them.     * Analyze the factors controlling the availability of mineral resources and the environmental impact of their development.     * Understand the relationship between human population growth and resource utilization.     * Examine the roles of recycling and sustainability in mineral use.

Understanding Minerals

• Geological Definition: A mineral is a substance that must meet four distinct criteria:     1. Naturally occurring solid: It must exist in nature, not be synthetic (e.g., steel is not a mineral because it is man-made).     2. Inorganic process formation: It is formed through inorganic means. Bones and teeth are not minerals because they are formed by organic processes, although fossilized teeth may become minerals through mineralization.     3. Characteristic crystal structure: It has a specific internal arrangement of atoms in an orderly crystalline lattice.     4. Specific chemical composition: It has a chemical formula where elements combine in specific ratios (e.g., Quartz is $SiO_2$; Phlogopite, a form of mica, is $KMg_3AlSi_3O_{10}(OH)_2$).
• Common Mineral Examples and Exclusions:     * Ice: Glacial ice is a mineral ($H_2O$) as it occurs naturally as hexagonal crystals. Ice cubes in a freezer are not considered minerals because they are human-made.     * Quartz: A recognizable mineral with the formula $SiO_2$.     * Diamond: A mineral composed of carbon; one notable mine at Point Lake, NW Territories, Canada, was discovered in 1991 ($1.47 \text{ billion}$ value; Canada is the 4th largest diamond producer globally).     * Opal: An "opal" is a mineraloid rather than a true mineral because it lacks a crystalline structure and a specific chemical composition.     * Glass and Petroleum: Glass lacks a crystal structure; petroleum and natural gas are not solids and are derived from organic matter, therefore they are not minerals.     * Coal: Not a mineral because it is derived from the remains of plant material and organic processes.

Identifying Minerals via Physical Properties

• Color: While some minerals have diagnostic colors (e.g., Sulfur is yellow, Azurite is blue), color is often unreliable as two different minerals may share a color, or the same mineral can occur in different colors due to impurities.
• Streak: The color of a mineral in its powdered form, created by rubbing it against an unglazed porcelain plate. This is often more diagnostic than the mineral's surface color.
• Luster: The quality and intensity of light reflected from the surface. Types include:     * Metallic: E.g., Pyrite ("fool's gold").     * Vitreous: Glassy, like Quartz.     * Resinous: Like dried tree resin, seen in Sphalerite ($ZnS$).     * Pearly: Seen in Talc.     * Dull: No shine.
• Crystal Form and Habit: The distinctive shape or flat/planar surfaces (crystal faces) formed during growth through crystallization or precipitation (e.g., Halite/Table salt has a cubic habit).
• Cleavage: The manner in which minerals break along planes of weakness. Examples include:     * One-directional: Mica.     * Two-directional: Potassium feldspar.     * Three-directional: Halite.
• Hardness (Mohs Hardness Scale): A scale from 1 (softest) to 10 (hardest) based on scratch resistance.     1. Talc (Common object: Fingernail at $2.5$)     2. Gypsum     3. Calcite (Common object: Copper Penny at $3.5$)     4. Fluorite     5. Apatite (Common object: Knife/Glass Plate at $5.5$)     6. Orthoclase (Common object: Steel Nail at $6.5$)     7. Quartz     8. Topaz (Common object: Masonry Drill Bit at $8.5$)     9. Corundum     10. Diamond

Hazardous Minerals and Environmental Health

• Asbestos: Part of the Serpentine or Amphibole groups, characterized by thin, long fibrous crystals. Exposure is linked to lung cancer and respiratory disease. It was historically used in roofing, fencing, wall materials, and soundproofing. Asbestos-related deaths are described as being at an epidemic scale in the U.S., exceeding deaths from tuberculosis, drowning, and accidental firearm discharge in 2002.
• Mercury ($Hg$): A toxic heavy metal extracted from Cinnabar ($HgS$). It is highly toxic, non-biodegradable, and can be absorbed through the skin. Mercury concentrations increase up the food chain (biomagnification) from aquatic insects to insect-eating fish, fish-eating fish, and finally humans. In 2008, U.S. mercury emissions totaled $89,422\text{ lb}$ ($44.7\text{ tons or } 40,561\text{ kg}$).
• Arsenic ($As$): Often associated with sulfur in minerals like Arsenopyrite ($FeAsS$). It causes respiratory problems if inhaled and is a major groundwater contaminant. Over $137 \text{ million}$ people in more than $70 \text{ countries}$ are affected by arsenic poisoning in drinking water. The drinking water standard is $10\text{ ppb}$.

Rocks and the Rock Cycle

• Rock Definition: Solid aggregates of one or more minerals, sometimes containing non-mineral content. Rocks serve as geological clues to Earth's history.
• The Rock Cycle: A process of conversion and reconstitution:     * Weathering: Breaking down rocks on the surface.     * Melting: Creating magma.     * Metamorphism: Changing form due to pressure and temperature.
• Igneous Rocks: Formed from cooling magma. Texture depends on cooling rate:     * Slow cooling: Forms large crystals (Coarse-grained, e.g., Plutonic/Intrusive rocks like Granite).     * Rapid cooling: Forms small crystals (Fine-grained, e.g., Volcanic/Extrusive rocks like Basalt).     * Extremely rapid cooling: Produces glassy textures with no crystals.
• Chemical Classification of Igneous Rocks:     * Felsic: High silica content ($70-75\% \text{ } SiO_2$); light-colored; rich in quartz and feldspar (e.g., Granite).     * Intermediate: Approximately $60\% \text{ } SiO_2$ (e.g., Diorite/Andesite).     * Mafic: Lower silica content ($45-50\% \text{ } SiO_2$); dark-colored; rich in iron, olivine, and pyroxene (e.g., Basalt, which makes up the ocean floor).
• Sedimentary Rocks: Formed at low temperature and pressure from sediments through Lithification (compaction, cementation, and recrystallization).     * Detrital/Clastic: Formed from rock fragments (clasts). Examples: Conglomerate, Sandstone, Siltstone, Shale.     * Chemical: Formed via precipitation from water (e.g., Limestone, Salt deposits, Banded iron formation).
• Metamorphic Rocks: Rocks transformed by high pressure and temperature from existing igneous or sedimentary precursors.

Mineral Economics and Availability

• The Resource-Reserve Distinction:     * RESOURCE: Elements, compounds, minerals, or rocks in a form that has the potential to be extracted at a profit.     * RESERVE: The portion of the resource that is currently identified and legally extractable at a profit.
• Factors Governing Availability: Availability is limited not just by physical exhaustion but by mineral economics. Strategies to address limits include finding new resources, finding substitutes, recycling, increasing efficiency, or doing without.
• Utilization Categories:     * Metal Production: Abundant metals (Iron, Aluminum, Chromium, etc.) and Rare metals (Gold, Silver, Copper, Zinc, etc.).     * Building materials: Aggregates, sand, crushed stone, tile clays.     * Chemical/Petrochemical industry: Produced from natural gas or crude oil.     * Agriculture: Fertilizers and nutrients.

The Mining Life Cycle and Environmental Impact

• Mining Techniques:     1. Open-pit mining: Used for surface deposits (e.g., Bingham Canyon Copper Mine in Utah, the largest excavation on Earth at $4\text{ km}$ wide and $1\text{ km}$ deep).     2. Underground mining: Used for deep deposits. Eight of the ten deepest mines are in South Africa; two are in Ontario, Canada (Kidd Creek and Creighton).     3. Pan mining: Used for alluvial deposits.
• Development Cycle:     * Exploration ($8-10+ \text{ years}$): Mapping, drilling, permitting.     * Construction ($1-3 \text{ years}$): Building infrastructure like roads and power grids.     * Operation ($10-30 \text{ years}$): Extraction and ongoing exploration.     * Closure and Reclamation ($1-2 \text{ years}$ for closure, $1-4 \text{ years}$ for reclamation): Environmental remediation, reforestation, and land redevelopment.     * Monitoring ($5+ \text{ years}$): Ensuring long-term safety and stability.
• Environmental Consequences:     * Land Disturbance: In the U.S., $60\%$ of mining land is for extraction, and $40\%$ for waste disposal.     * Waste Generation: Over the last $100 \text{ years}$, U.S. mining has produced $50 \text{ billion}$ tons of waste. Current average production is $1-2 \text{ billion}$ tons annually.     * Pollution: Acid mine drainage (white streaks of leached minerals in runoff), habitat degradation, deforestation, and water pollution.     * Gold Mining and Mercury: Inorganic mercury used to recover gold can transform into Methyl-Mercury, the most toxic organic form, which enters the environment through the food chain.