Module 3: Minerals

Overview

• Focus on the definition, importance, and physical properties of minerals.
• Encourages familiarity with common rock-forming minerals using physical and chemical properties.
• Includes experiments to strengthen knowledge and skills.

Definition of Minerals

• Minerals are the building blocks of rocks.
• The Earth's crust is composed of various rocks, each an aggregate of one or more minerals.
• Mineralogy: The study of minerals.
• Mineralogist: A person who studies minerals.

Characteristics of Minerals

To be considered a mineral, a substance must have the following characteristics:

1. Naturally Occurring: Formed by natural processes, not man-made.
2. Inorganic: Not made from plants or animals; no carbon-based compounds.
3. Homogeneous Solid: Uniform structure throughout.
4. Definite Chemical Composition: Specific and consistent chemical makeup.
5. Crystalline Structure: Ordered arrangement of atoms, ions, or molecules.

• Mineraloid: Non-crystalline mineral-like substances (e.g., Opal).

Importance of Minerals

• Essential in everyday life, used in various applications such as glass (neural parts), pencils (graphite), toothpaste (fluoride), coins and wiring (chalcopyrite), etc.
• Humans require 16 essential minerals for survival (e.g., sodium, potassium, calcium).
• Over 4,200 minerals exist, but only 100 are common (rare ones include gold, silver).

Physical Properties of Minerals

Mineralogists identify minerals based on their chemical and physical properties:

1. Luster: Brightness of light reflected from mineral surfaces. Types include:

   • Metallic
   • Non-metallic (e.g., glassy, earthy, silky)

2. Color: Often variable and not reliable for identification.

3. Streak: Color of the mineral's powder, more consistent than surface color.

4. Hardness: Scratchability of a mineral, measured by Mohs hardness scale (1 to 10).

   • Examples: Talc (1), Gypsum (2), Diamond (10).

5. Cleavage: Ability of a mineral to break along planes.

   • Examples: Muscovite (one direction), Feldspar (two directions).

6. Specific Gravity: Ratio of the mass of a mineral to the mass of an equal volume of water.

7. Crystal Form or Habit: External shape of crystals or crystal groups.

8. Tenacity: Mineral cohesiveness, including:

   • Brittleness (e.g., Pyrite)
   • Malleability (e.g., Gold)
   • Ductility (e.g., Copper)
   • Flexibility and Elasticity (e.g., Biotite)
   • Sectility (e.g., Gypsum)

9. Other Special Properties:

   • Taste (e.g., Halite tastes salty)
   • Odor (e.g., Clay minerals)
   • Striations
   • Magnetism
   • Double Refraction (e.g., Calcite)
   • X-ray fingerprints
   • Chemical Tests (e.g., Calcite reacts with hydrochloric acid)

Identifying Minerals

• Correct sequence used by mineralogists:
  1. Luster
  2. Hardness
  3. Color
  4. Streak
  5. Crystal form/habit
  6. Cleavage
  7. Specific gravity
  8. Other properties

Conclusion

• Discussion on module three in minerals concludes with a comprehensive understanding of the definition, importance, and properties of minerals.