Primary rocks are formed at the first instance in the geological time scale and are result of solidification of magma and lava like granite, gabbro, pegmatite, basalt.
- Hard and resistant to erosion.
- Sudden cooling results in small and smooth grains and slow cooling results in large-sized grains.
- Primarily eroded by mechanical weathering.
- Water seepage is low and hence does not have high groundwater levels
- Lack fossil deposits but are rich in ferrous deposits.
Depending upon their location there are following types of primary rocks:
- Formed due to cooling and solidification of magma within the Earth crust.
- Associated with features like dykes, batholiths, laccoliths, phacoliths etc.
- They generally have large crystals.
- Formed due to cooling and solidification of lava on the surface of the Earth.
- They have small-sized crystals.
These primary rocks can help us to study the earth’s interior and have high economic importance. UNESCO’s global framework for geo-heritage can go a long way in guiding countries to conserve their landforms.