names of crystalline igneous rocks
Texture determines whether an igneous rock is defined as Intrusive (coarsely crystalline) or Extrusive (finely crystalline). Intrusive Igneous Rocks. 1. Fig. 3.2: Intrusive igneous rocks form at some depth within the crust due to slow cooling of magma, resulting in formation of large crystals.Individual crystals can be seen with the naked eye. These rocks are termed texturally as coarsely crystalline or phaneritic.. Fig. 3.2: Intrusive igneous rocks form at some depth within the crust due to slow cooling of magma, resulting in formation of large crystals. Individual crystals can be seen with the naked eye. These rocks are termed texturally as coarsely crystalline or phaneritic.