Minerals

Definition of Terms

  • Mineral: naturally occurring, inorganic, solid with an orderly crystalline structure and a definite chemical composition; building blocks of rocks.

  • Ice vs water: ice (solid, crystalline) is a mineral; liquid water is not. Snow can be considered mineral when solid and crystalline.

  • Key takeaway: Minerals are solid, inorganic, naturally formed with a defined composition and crystalline structure.

Mineral Properties

  • Hardness: a measure of a mineral's resistance to scratching; Mohs hardness scale describes hardness on a 1\leq H \leq 10 scale.

  • Luster: quality and intensity of reflected light; categories include metallic, nonmetallic (vitreous, glassy; waxy; silky; pearly; resinous; earthy).

  • Crystal form/habit: geometric forms from repeating atomic patterns; e.g., gold atoms arranged cubic; real crystals may be imperfect.

  • Cleavage vs Fracture:

    • Cleavage: tendency to split along planes of weakness, forming smooth surfaces.

    • Fracture: breaks along curved or irregular surfaces.

  • Color vs Streak:

    • Color: surface color of mineral.

    • Streak: color of powdered mineral.

  • Density / Specific gravity: ratio of mineral mass to its volume; specific gravity = density(mineral) / density(water).

  • Example: Halite (table salt)

    • Formula: NaCl

    • Luster: non-metallic, vitreous

    • Hardness: 2-2.5

    • Color/Streak: White

    • Crystal form: Cubic; Cleavage: Perfect cubic

    • Specific gravity: approx. 2.2

    • Other: salty taste; very soluble; produces reddish spark in flame

Mineral Groups

  • Silicate minerals:

    • Contain silicon and oxygen (SiO4) tetrahedra and may include metals.

    • Make up >90\% of Earth’s crust.

    • Often contain Al, Fe, Mg, etc.

    • Examples: Quartz (SiO2), Feldspars, Olivine, Muscovite, etc.

  • Non-silicate minerals:

    • Do not contain SiO4 tetrahedra.

    • Examples: Carbonates (e.g., CaCO3), Oxides (e.g., Fe2O3), Sulfates (e.g., CaSO4), Sulfides, Halides (e.g., NaCl), Native elements (e.g., Au, Cu).

Mineral Groups (Table Snapshot)

  • Native elements: Gold, Silver, Copper, Diamond, Graphite, etc.

  • Oxides: Hematite (Fe2O3), Magnetite (Fe3O4), etc.

  • Sulfides: Pyrite (FeS2), Galena (PbS), etc.

  • Carbonates: Calcite (CaCO3), Dolomite (CaMg(CO3)2)

  • Halides: Halite (NaCl), Fluorite (CaF2)

  • Sulfates: Gypsum (CaSO4·2H2O), Anhydrite (CaSO4)

Periodic Table (Essentials)

  • Organized by atomic number, left to right and top to bottom.

  • Periodic trends: electron configurations, reactivity, and properties emerge across periods and groups.

Seatwork: Minerals (Conceptual Questions)

  • Why is glacier ice a mineral but river water is not?

    • Ice is a solid with a crystalline structure formed naturally; water is a liquid and not crystalline.

  • Major groups of minerals: features of Silicate vs Non-silicate.

    • Silicates: Si and O frameworks (SiO4); include most crust minerals (e.g., Quartz, Feldspars).

    • Non-silicates: lack SiO4 frameworks; include carbonates, oxides, sulfides, sulfates, halides, native elements.

  • Four types of nonsilicate minerals:

    • Carbonates (e.g., Calcite)

    • Oxides (e.g., Hematite)

    • Sulfides (e.g., Pyrite)

    • Halides (e.g., Halite)

  • Cleavage vs Fracture:

    • Cleavage: clean, flat surfaces along planes of weakness.

    • Fracture: irregular or curved break surfaces.

  • Unknown mineral hardness exercise:

    • If Calcite (Mohs hardness 3) does not scratch the unknown and Apatite (Mohs hardness 5) does scratch the unknown, then

    • The unknown hardness 3 < H_{unknown} < 5 , harder than 3 but softer than 5). An approximate value could be around 4 depending on the mineral.