Introduction to Mineralogy
Fundamentals, classification, properties, and significance
1. What Is Mineralogy?
- Definition – The scientific study of minerals: naturally occurring, inorganic solids with a defined chemical composition and ordered atomic structure.
- Scope – Includes identification, classification, physical & chemical properties, formation processes, and economic uses.
- Relation to other fields – Overlaps with crystallography, petrology, geochemistry, materials science, and environmental science.
2. Basic Concepts
| Concept |
Description |
| Mineral Species |
A distinct chemical composition and crystal structure (e.g., quartz = SiO₂). |
| Mineral Group |
A set of species sharing a similar structural framework (e.g., feldspar group). |
| Crystal Lattice |
The three‑dimensional arrangement of atoms repeated periodically. |
| Unit Cell |
The smallest repeat unit of a crystal lattice; defined by lattice parameters (a, b, c, α, β, γ). |
| Polymorphism |
Different crystal structures for the same chemical composition (e.g., calcite vs. aragonite, both CaCO₃). |
| Solid Solution |
Continuous chemical variation between end‑member minerals (e.g., olivine: (Mg,Fe)₂SiO₄). |
3. Classification of Minerals
3.1 By Chemical Composition (Dana & Strunz systems)
| Class |
Main Anions / Elements |
Typical Examples |
| Native Elements |
Pure elements (metals, semimetals) |
Gold (Au), Diamond (C) |
| Silicates |
SiO₄ tetrahedra |
Quartz, Feldspar, Mica |
| Oxides |
O²⁻ |
Hematite (Fe₂O₃), Rutile (TiO₂) |
| Sulfides |
S²⁻ |
Pyrite (FeS₂), Galena (PbS) |
| Carbonates |
CO₃²⁻ |
Calcite (CaCO₃), Dolomite (CaMg(CO₃)₂) |
| Halides |
Cl⁻, F⁻, Br⁻ |
Halite (NaCl), Fluorite (CaF₂) |
| Phosphates |
PO₄³⁻ |
Apatite (Ca₅(PO₄)₃(F,Cl,OH)) |
| Sulfates |
SO₄²⁻ |
Gypsum (CaSO₄·2H₂O) |
| Phyllosilicates (sheet silicates) |
Si₂O₅ layers |
Mica, Talc |
| Tectosilicates (framework silicates) |
SiO₂ framework |
Quartz, Feldspar |
3.2 By Crystal System
| System |
Axes & Angles |
Representative Minerals |
| Cubic (Isometric) |
a = b = c; α = β = γ = 90° |
Halite, Pyrite |
| Tetragonal |
a = b ≠ c; α = β = γ = 90° |
Zircon |
| Hexagonal |
a = b ≠ c; α = β = 90°, γ = 120° |
Beryl |
| Trigonal |
a = b ≠ c; α = β = 90°, γ = 120° (often treated as a subset of hexagonal) |
Calcite |
| **Orthorh |
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