Ch 2 minerals

Bonus Questions

  • March 2025 earthquake = Myanmar

Chapter 2: Minerals

The Building Blocks of Rocks

Definition of Minerals

  • Minerals are:

    • Naturally occurring

    • Inorganic

    • Crystalline solids

    • Have a narrowly defined chemical composition

    • Exhibit characteristic physical properties

  • Isotopes:

    • Atoms with the same atomic number but different mass numbers.

    • Example: Carbon-12, Carbon-13, and Carbon-14 all have six protons, hence the same atomic number.

Mineral Characteristics

  • Over 4,500 minerals identified, but fewer than 25 are common rock-forming minerals.

  • Most abundant elements in Earth's crust by % weight:

    • Oxygen: 46.6%

    • Silicon: 27.7%

Groups of Minerals

Main mineral examples:

  • Halite = NaCl

  • Quartz = SiO2

  • Olivine = Mg,Fe2SiO4

  • Gypsum = CaSO4,2H2O → white sands at mexico

Major Mineral Groups

  • Silicate minerals (SiO4)4-:

    • Most abundant in Earth’s crust.

  • Carbonates (CO3)2- :

  • Phosphates (PO4)3- :

Types of Silicates

  • Nonferromagnesian silicates:

    • light in colour (quartz)

  • Ferromagnesian silicates:

    • dark in color (olivine)

Carbonate Minerals

  • Calcite and Aragonite (CaCO3)

  • Dolomite

Identification of Minerals

  • Color:

    • Can vary based on impurities or range of chemical formula.

  • Streak:

    • The color of the powdered mineral left on a streak plate. More reliable for identification than color.

  • Luster:

    • The appearance of the mineral in reflected light, classified as metallic or nonmetallic

Additional Identification Techniques

Physical properties of minerals

  • internal structure and chemical composition

  • Polymorphism:

    • Some elements and compounds can form multiple minerals (e.g.,

    • (Graphite, Diamond) CaCO3

    • (Calcite, Aragonite) C

Cleavage and Fracture

Cleavage

  • break along planes between weak bonds

  • planar directions

Fracture

  • Fracture:

    • broken without any preferred cleavage directions.

Hardness and Specific Gravity

Hardness

  • Based on Moh's hardness scale from 1 to 10:

    • 10: Diamond

    • 7: Quartz

    • 3: Calcite

    • 2: Gypsum

    • 1: Talc

Additional Useful Properties for Mineral Identification

  • Taste (e.g., Halite is salty)

  • Feel

  • Magnetism

  • Double refraction (optical property)

  • Reaction with dilute hydrochloric acid (e.g., Calcite, Aragonite react; forms bubbles).

Origin of Minerals

  • Crystallization from molten rock material (magma).

  • Precipitation from sea or lake water (e.g., Halite, Gypsum).

  • biomineralization = carbonate minerals