Igneous rocks are formed through crystallisation process while cooling of magma
Types based on formation
Plutonic Rocks (Intrusive)
cooled and solidify below the crust
- Granite
- Diorite
- Gabbro
- Peridotite
Volcanic Rocks (Extrusive)
cooled and solidify on the surface
- Rhyolite
- Andesite
- Bassalt
- Komatite
Types based on Silica content
Felsic Rocks
High Silica content over 65%
- Granite
- Rhyolite
Intermediate Rocks
55 to 65% Silica content
- Diorite
- Andesite
Mafic Rocks
45 to 55% Silica content
- Gabbro
- Basalt
Ultramafic Rocks
less than 45% Silica content
- Peridotite
- Komatite
Types based on Mineral content
vary based on feldspar, quartz, olivine, pyroxene content — composition affects colour and density
Types based on Elemental content
vary based on iron, magnesium, calcium and potassium content