1. Igneous Rocks:
* Formation: Formed from the cooling and solidification of magma (molten rock) or lava.
* Characteristics:
* Often have a crystalline texture (interlocking crystals).
* Can be classified further based on texture (fine-grained, coarse-grained) and mineral composition.
* Examples: Granite, basalt, obsidian.
2. Sedimentary Rocks:
* Formation: Formed from the accumulation and cementation of sediments (rock fragments, minerals, organic matter).
* Characteristics:
* Often have layered or banded appearance.
* May contain fossils.
* Can be classified further based on grain size and composition.
* Examples: Sandstone, limestone, shale.
3. Metamorphic Rocks:
* Formation: Formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are transformed by heat, pressure, or chemical reactions.
* Characteristics:
* Often have a foliated texture (layers or bands).
* May show signs of recrystallization or mineral growth.
* Examples: Marble, slate, gneiss.
Additional Characteristics Used for Classification:
* Mineral Composition: The specific types of minerals present in the rock.
* Texture: The arrangement and size of grains or crystals within the rock.
* Color: While not always a reliable indicator, color can be helpful in identifying certain rock types.
* Hardness: A measure of the rock's resistance to scratching.
* Cleavage: The tendency of a rock to break along specific planes.
* Density: The mass of the rock per unit volume.
These characteristics are used in combination to create a comprehensive classification system for rocks.
