Built by a geologist

Minerals: The Building Blocks

Minerals: The Building Blocks Minerals are the fundamental building blocks of rocks — and understanding them is the foundation of all geology. What Is a Mineral? A mineral must meet five criteria: 1. Naturally occurring — Not made by humans synthetic diamonds are not minerals 2. Inorganic — Not produced by living organisms coal is not a mineral 3. Solid — Must have a fixed shape water is not a mineral, but ice is 4. Definite chemical composition — A specific formula or narrow range e.g., quartz = SiO₂ 5. Ordered crystal structure — Atoms arranged in a repeating 3D pattern The Major Mineral Groups Minerals are classified by their chemistry: | Group | Examples | Notes | |-------|----------|-------| | Silicates | Quartz, feldspar, mica, olivine | Make up 90% of Earth's crust | | Carbonates | Calcite, dolomite | React with acid fizz test | | Oxides | Hematite, magnetite | Important ore minerals | | Sulfides | Pyrite, galena, chalcopyrite | Many metallic ore minerals | | Sulfates | Gypsum, barite | Often formed by evaporation | | Halides | Halite rock salt , fluorite | Formed by evaporation | | Native elements | Gold, silver, copper, diamond | Elements occurring in pure form | Physical Properties for Identification Geologists identify minerals using observable properties: - Hardness — Resistance to scratching Mohs scale: 1 = talc, 10 = diamond - Luster — How light reflects: metallic, vitreous glassy , earthy, silky, etc. - Streak — Color of the powdered mineral scraped on a porcelain plate - Cleavage — Tendency to break along flat planes - Fracture — How it breaks when not along cleavage conchoidal, irregular, etc. - Color — Often unreliable many minerals come in multiple colors - Crystal form — The external shape reflecting internal atomic arrangement - Specific gravity — Density relative to water Why Minerals Matter - Every metal we use was once locked in a mineral - Building materials cement, glass, ceramics come from minerals - Gemstones are simply beautiful mineral crystals - Soil forms from the weathering of minerals - Understanding minerals is essential for identifying rocks