2-1 minerology questions - Tagged

Minerals: Overview

Definition: Building blocks of rocks.
Known minerals: Approximately 5,000, with 50-100 new minerals identified each year.

Key Definitions:
- Mineral:
  - Naturally occurring
  - Inorganic solid
  - Ordered internal molecular structure
  - Definite chemical composition
- Rock:
  - Solid aggregate or mass of minerals.
Examples: Beryl with microcline from Pakistan.

Examples of materials that are NOT minerals include ivory, bone, seashells, coral, and petrified wood.

Crystalline Structure:
- Mineral atoms are arranged in an orderly framework known as a crystal lattice.
- Glass has a random arrangement, lacking a specific pattern, unlike quartz crystals.
Galena Atomic Structure:
- Cubic structure allows for cubic cleavage and distinctive crystal shape.

Ionic Bonding:
- Involves the transfer of electrons to form oppositely charged ions.
- Example: Halite (NaCl) shows ionic bonding via electron transfer.
Covalent Bonding:
- Involves sharing of electrons between atoms; generally stronger than ionic bonds.

Polymorphs:
- Example: Diamond and graphite; both are forms of carbon but have different structures and properties.
  - Diamond: Strong covalent bonds in a 3-D grid.
  - Graphite: 2-D sheets with weak Van der Waals bonds.

Crystal Form: External expression of atomic arrangement, often competing for space.
Luster Types:
- Metallic
- Nonmetallic
  - Examples include Pearly, Vitreous, Resinous, Silky, Dull, Earthy.
Color:
- Highly variable and unreliable for identification; gemstones often exhibit exotic colors.
Streak:
- Color of a mineral in powdered form, helpful for distinguishing between forms of the same mineral.
Hardness:
- Measured by Mohs scale, which assesses resistance to scratching.
  - Mohs Scale:
    - Diamond (10), Corundum (9), Topaz (8), Quartz (7), etc.
Cleavage:
- Planes of weak bonding leading to flat, shiny surfaces; described by the number of planes and angles.
Fracture Types:
- Smooth, Rough, Splintery, Irregular, Conchoidal.

Rock-forming minerals: Comprise >98% of continental crust; important for understanding Earth’s structure.
Silicates:
- Most abundant mineral group, characterized by the silicon-oxygen tetrahedron.
- Various structures (e.g., isolated tetrahedra, ring structures, chains, sheets).

Olivine: High-temperature Fe-Mg silicate.
Pyroxene Group: Single-chain silicates with distinctive cleavages.
Amphibole Group: Double-chain silicates with characteristic angles.
Mica Group: Sheet structures with one direction of cleavage (Biotite and Muscovite).
Feldspar Group: Most common, characterized by a 3-D framework.

Carbonates:
- Includes limestone, dolostone; effervesce with dilute HCl (example: Calcite).
Economic Value:
- Varieties like Hematite (iron ore), Halite (salt), Sphalerite (zinc ore), Native Copper (copper).