Classification of Rocks
Rocks can be categorized based on their formation process, physical traits, and chemical makeup. Below is a detailed overview of each classification criterion:
1. Geological Formation
- Igneous Rocks: These rocks form from the solidification of molten magma or lava. They are known for their crystalline texture and are often found in volcanic regions.
- Sedimentary Rocks: Formed from the compaction and cementation of mineral and organic particles, these rocks often display distinct layers and may contain fossils.
- Metamorphic Rocks: Resulting from the transformation of existing rocks under high pressure and temperature, metamorphic rocks are characterized by their dense and foliated structure.
2. Physical Characteristics
- Stratified: These rocks display distinct layers or strata, which are typically formed from sedimentary processes.
- Unstratified: Lacking any obvious layering, these rocks are often massive and may be igneous or metamorphic in origin.
- Foliated: These rocks have a banded or layered appearance due to the alignment of minerals under directional pressure, common in metamorphic rocks.
3. Chemical Composition
- Argillaceous: These rocks are rich in clay minerals and tend to be soft and easily weathered.
- Siliceous: Containing a high amount of silica, siliceous rocks are typically hard and resistant to weathering.
- Calcareous: Composed primarily of calcium carbonate, these rocks include limestone and marble, and they react with acid.