Mineral Identification

Mineral Color

• Color is not a reliable characteristic for identifying minerals.
• Example: Quartz can come in many colors (white, blue, green).
• Different minerals can share the same color.

Hardness

• Measured using a piece of glass (hardness 5.5 on the Mohs scale).
• Scratch test method:
  • Place glass on a table.
  • Try scratching the glass with a mineral sample.
  • If it scratches, the mineral's hardness is greater than 5.5.
  • If it doesn't, the mineral's hardness is less than 5.5.

Luster

• Describes how light reflects off the surface of a mineral.
• Two types for class: metallic and non-metallic.
• Metallic: Minerals that look like metal (e.g., Galena, Pyrite).
• Non-metallic: Minerals that do not look like metal (e.g., Olivine, Gypsum).

Breakage: Cleavage vs. Fracture

• Fracture: Random breakage with irregular shapes.
  • Examples: Olivine, Hematite, Quartz, Pyrite.
• Cleavage: Predictable breaking with flat surfaces.
  • Examples: Calcite (flat surfaces, predictable), Galena (90° angles), Halite, Biotite Mica (sheets).

Streak

• The color of a mineral in powdered form.
• Use streak plates (black and white ceramic tiles).
• Procedure:
  • Rub the mineral on the streak plate to create powder.
  • Observe the color of the streak.
• Examples:
  • Hematite: Reddish-brown streak.
  • Pyrite: Grayish-black streak.
  • Calcite: No streak or very faint white.

Other Properties

• Taste: Halite tastes salty (do not lick samples).
• Magnetism: Magnetite is magnetic.
• Double Refraction: Calcite doubles the image viewed through it.
• Reaction with Acid: Calcite fizzes when in contact with hydrochloric acid.