Minerals: Fracture and Specific Gravity

Properties of Minerals

• Fracture occurs when minerals break irregularly, without defined cleavage planes.
• Specific gravity indicates a mineral's weight relative to an equal volume of water; native metals typically exhibit high specific gravity.
• Examples of mineral properties:
  • Magnetite is strongly magnetic.
  • Sulfur has a distinctive odor.
  • Halite tastes salty.
  • Fluorite can disperse ultraviolet light into visible light.
  • Calcite reacts with acid, similar to dolomite but less effective in powdered form.

Mineral Groups

• Silicates: Composed of silicon and oxygen; make up over 90% of rock-forming minerals.
  • Most common elements in the Earth's crust include Silicon (46.6%), Oxygen (27.7%), Aluminum (8.1%), Iron (5.0%), Calcium (3.6%), Magnesium (3.1%), Sodium (2.8%), and Potassium (2.6%).
• Oxides: Minerals with oxygen anion combined with metal ions.
• Sulfates: Contains sulfur and oxygen anion (SO4) with other ions.
• Sulfides: Composed of sulfur anion (S2) with metal ions; some are sources of economically valuable metals like copper, lead, and zinc.
• Carbonates: Contain the carbonate anion (CO3) with other elements.
• Native Elements: Form as distinct, individual elements; include metals and semi-metals.
  • Metals (e.g., gold, lead) have high thermal and electrical conductivity.
  • Semi-metals (e.g., arsenic, bismuth) are more fragile and less conductive.
  • Nonmetals (e.g., sulfur, diamond) are not conductive.
• Halides: Minerals composed of halogen elements combined with other elements.

Rocks

• Rocks are naturally formed combinations of organic and inorganic materials that consist of one or more minerals.
• Classification depends on formation, composition, and texture.
• Rocks undergo continuous changes through the rock cycle.

Igneous Rocks

• Formed from the cooling of magma or lava.
• Magma formation occurs through:
  • Heating of existing rock.
  • Release of pressure.
  • Changes in rock composition.
• Magma freezes at temperatures between 700 °C and 1,250 °C.
• Two types of igneous rocks:
  • Intrusive Igneous Rocks: Formed beneath the Earth's surface (e.g., gabbro, granite).
  • Extrusive Igneous Rocks: Formed on the surface (lava).

Characteristics of Minerals

• Minerals must be naturally occurring, inorganic, solid with an orderly crystalline structure, and have a definable chemical composition.
• Water is excluded as a mineral since it is not solid.
• Pearls, though naturally occurring and crystalline, are organic and thus not categorized as minerals.

Objectives of Study

• Identify physical and chemical properties of minerals.
• Understand the relationship between rock types and their formation processes.
• Illustrate the rock cycle.
• Recognize the significance of minerals in society.

This quiz explores key concepts related to minerals, focusing on how they break, specifically through fractures rather than cleavage. Additionally, it covers the concept of specific gravity in minerals, comparing their weight to water. Test your knowledge of mineral properties and characteristics!