Lesson 5: Minerals

Earth's Minerals

Definition of Minerals

• Inorganic

• Naturally occurring

• Solid with orderly crystalline structure

• Definite chemical composition

• Building blocks of rocks

Mineral Groups

• Silicates: Contain Silicon & Oxygen (most abundant in Earth’s crust)

  • Make up 90% of common rock-forming minerals

  • e.g., Feldspar, Quartz

• Oxides: Made of oxygen and metal ions

  • e.g., Chrysoberyl, Alexandrite chrysoberyl crystal

• Sulfates: Contain sulfur and oxygen

• Sulfides: Contain sulfur and metallic elements

• Carbonates: Contain carbonate (CO₃) combined with other elements

  • e.g., Dolomite, Calcite, Rhodochrosite

• Halides: Combine halogen elements (like chlorine or fluorine) with metals

  • e.g., Halite (salt), Fluorite

Native Elements: Made of single elements

a. Metallic and Intermetals

• high thermal, conductive, shiny, soft (e.g., gold, lead)

b. Non-metallic

• non-conductive (e.g., sulfur, diamond)

c. Semi-metallic

• fragile, less conductive (e.g., arsenic, bismuth)

Properties of Minerals

• Luster:

  • How a mineral reflects light

• Hardness:

  • Resistance to scratching

Measured by Mohs Scale: (Friedrich Mohs, 1812)

1.) Talc

2.) Gypsum

---------- Fingernail

3.) Calcite

---------- Calcite

4.) Flourite

5.) Apatite

---------- Knife/Glass

6.) Feldspar

---------- Steel

7.) Quartz

8.) Topaz

9.) Corundum

10.) Diamond

Crystal Form/Habit – Common external shape/growth pattern of crystals

• Color and Streak

  • Color may vary; streak is mineral’s powdered form

• Cleavage: Tendency to break along flat planes

  • e.g., Calcite shows good cleavage

• Fracture: Breaks with uneven or jagged surfaces

• Specific Gravity: Density compared to water

  • Metallic minerals = higher

    • e.g., gold, silver

  • Non-metallic = lower

    • e.g., sulfur, gypsum

Other Properties

• Magnetism

• Odor

• Taste

• Acid reaction

• Tenacity: Resistance to breaking or deforming