Minerals and Their Economic Importance

Mineral Classification and Properties

• Obsidian: Volcanic glass, non-crystalline (amorphous).
• Jet: Organic lignite, a precursor to coal, non-crystalline.
• Opal: Amorphous silica with chemical composition SiO2·nH2O.

Economic Importance of Minerals

• Copper: Used for electric cables, wires, and switches.
• Feldspar: Utilized in glass, ceramics, and sanitary ware.
• Calcite: Found in toothpaste, construction, and antacid tablets.
• Iron: Major component in buildings, magnets, and cars.
• Halite: Commonly known as table salt, used in food preservation.
• Graphite: Employed in electrical applications, pencils, and lubricants.

Mineral Groups

• Rock-forming Minerals: Abundant minerals in various rocks, divided into:

  • Primary Minerals: Crystallized directly from magma or lava, including essential (define rock) and accessory (do not define rock) minerals.
    • Essential examples: Feldspar, quartz, biotite.
    • Accessory examples: Zircon, sphene, apatite (major source of phosphorus).
  • Secondary Minerals: Formed by the alteration of primary minerals through weathering/hydrothermal processes (e.g., clay minerals).

• Ore-forming Minerals: Minerals suitable for metal extraction.

  • Examples: Hematite (Fe2O3 - iron), galena (PbS - lead), malachite (Cu2(CO3)(OH)2 - copper), native gold (Au).

Factors Affecting Ore Minerals

• Suitability determined by:
  • Ease of separation from gangue and concentration for smelting.
  • Energy required to release metals from mineral bonds; sulfide, oxide, or hydroxide minerals require less energy to smelt than silicate minerals.

Mafic and Felsic Minerals

• Mafic Minerals: Rich in iron and magnesium, generally dark-colored (e.g., olivine, pyroxene).
• Felsic Minerals: Light-colored (e.g., quartz, feldspar).

Gangue and Metallic Minerals

• Gangue Minerals: Non-valuable minerals associated with ore minerals.
• Metallic Minerals: Sources of metals such as iron, aluminum, copper, and more.

Industrial Minerals

• Mined for physical properties such as hardness, color, and luster.
• Applications include abrasives (garnet), cosmetics (calcite, talc), and agricultural uses (phosphates).

Mineral Nomenclature

• Mineral names based on physical properties, chemical composition, locality, or mineralogist.
• Examples include:
  • Albite: Named for its white color (Latin: albus).
  • Chromite: Contains chromium.

Mineral Identification Techniques

• Identified by physical properties (color, luster, hardness) or advanced methods (XRD, chemical analysis).
• Test methods include flame tests, where a clean wire loop is dipped into a sample to observe emission colors.

Carbonate Minerals

• Key constituents of sedimentary rocks, also found in igneous and metamorphic rocks.
• Identification assists via chemical staining and various discrimination tests (e.g., between calcite and dolomite).

Silicate Minerals Classification

Silicate minerals are the most common on Earth; classified into 7 sub-groups based on their silicate anion structure:

• Nesosilicates: Independent tetrahedra (e.g., Olivine).
• Sorosilicates: Double tetrahedra (e.g., Epidote).
• Inosilicates: Single-chain (e.g., Pyroxene) and double-chain (e.g., Amphibole).
• Phyllosilicates: Sheet structure (e.g., Mica).
• Tectosilicates: 3D frameworks (e.g., Feldspar, Quartz).

Metamorphism and Its Types

• Metamorphism occurs under high temperature and pressure, transforming existing rocks.
• Common metamorphic minerals: garnet and serpentine.
• Types of metamorphism:
  • Contact Metamorphism: High temperature, low pressure, driven by nearby magma.
  • Regional Metamorphism: High temperature and pressure over large areas, usually at convergent plate boundaries.

Important Mineral Tests

• Tests for differentiating minerals include specific reactions with chemical solutions (e.g., Lemberg test for calcite and dolomite) and response to thermal tests for emissions in flame.

This quiz covers various minerals, including obsidian, jet, opal, and their characteristics. It also explores the economic importance of minerals like copper, feldspar, calcite, iron, halite, and graphite. Test your knowledge about the properties and uses of these vital resources.