Major Rock Types to Know for Physical Geology

Rocks are the building blocks of our planet, and understanding their types is key in Physical Geology. This overview covers igneous, sedimentary, and metamorphic rocks, highlighting their formation, characteristics, and significance in Earth's history and processes.

1. Igneous rocks

   • Formed from the cooling and solidification of molten rock (magma or lava).
   • Classified into two main types: intrusive (plutonic) and extrusive (volcanic).
   • Commonly contain minerals such as quartz, feldspar, and mica.

2. Sedimentary rocks

   • Formed from the accumulation and compaction of mineral and organic particles.
   • Often contain fossils and provide important information about Earth's history.
   • Classified into three main types: clastic, chemical, and organic.

3. Metamorphic rocks

   • Formed from the alteration of existing rocks due to heat, pressure, and chemically active fluids.
   • Can originate from igneous, sedimentary, or other metamorphic rocks.
   • Characterized by foliation (layering) or non-foliated textures.

4. Granite

   • A common intrusive igneous rock composed mainly of quartz, feldspar, and mica.
   • Known for its coarse-grained texture and durability.
   • Often used in construction and as a decorative stone.

5. Basalt

   • A fine-grained extrusive igneous rock formed from the rapid cooling of lava.
   • Typically dark in color and rich in iron and magnesium.
   • Commonly found in oceanic crust and volcanic islands.

6. Limestone

   • A sedimentary rock primarily composed of calcium carbonate (calcite).
   • Often forms in marine environments from the accumulation of shells and coral.
   • Used in construction, agriculture, and as a raw material in various industries.

7. Sandstone

   • A clastic sedimentary rock composed mainly of sand-sized mineral particles or rock fragments.
   • Often forms in desert or river environments and can contain fossils.
   • Used in construction and as a reservoir rock for oil and gas.

8. Shale

   • A fine-grained sedimentary rock formed from compacted clay and silt.
   • Often contains fossils and is known for its ability to split into thin layers.
   • Important source rock for oil and natural gas.

9. Marble

   • A metamorphic rock formed from the recrystallization of limestone under heat and pressure.
   • Known for its beauty and variety of colors, often used in sculpture and architecture.
   • Can contain distinctive patterns and veining.

10. Slate

    • A fine-grained metamorphic rock derived from shale, characterized by its ability to split into thin sheets.
    • Often used for roofing, flooring, and other architectural applications.
    • Forms under low-grade metamorphic conditions.

11. Gneiss

    • A high-grade metamorphic rock characterized by its banded or foliated appearance.
    • Formed from the alteration of granite or sedimentary rocks under intense heat and pressure.
    • Often contains a variety of minerals, including quartz, feldspar, and biotite.

12. Schist

    • A medium to high-grade metamorphic rock known for its pronounced foliation and shiny appearance due to mica content.
    • Forms from the metamorphism of shale or other sedimentary rocks.
    • Often contains garnet, kyanite, or other minerals, indicating specific metamorphic conditions.