igneous.jpgIgneous Rocks

These rocks are formed by the cooling of molten rocks called magma. The creation of these rocks form underground or on the surface. When the magma cools slowly underground (intrusive), the crystals are large enough to see by the human eye. On the other hand, when the rocks are cooled quickly on the surface (extrusive), the crystals are so small that a magnifier or microscope has to be used to see them.nlbowen2sm.jpg

History of Igneous Rocks

The word Igneous come from the Greek term, "out of the fire". Professor Norman L. Bowen summarized results of experiments done early in the 1900’s on crystallization of granitic magmas. These experiments showed that there is a definite sequence of minerals that crystallize as the temperature of magma is lowered: Start with a collection of molten magma and progressively cool it. Minerals will crystallize (solidify) in a order. Bowen’s Reaction Series represents a sequence that has implications for other types of rocks as well, although it is only used to determine the crystallization sequence in a molten magma (intrusive igneous rocks).

Application of Igneous Rocks

There are several examples for igneous rocks.
  • Granite: an igneous-plutonice rock with a medium to coarse grained that is high in silica , potassium, sodium, and quartz. Its used widely in construction ornamental stone and monuments.
  • Pumice: An igneous-volcanic rock, it is a porous, brittle variety of rhyolite and is light enough to float. It is used as an abrasive material in hand soaps, emery boards, etc.


  1. Beiser, A. (1988). Physical Science (2nd Edition). New York, NY: McGraw Hill
  2. Craig, L (2011). Physical Science Lab Book. Rock Hill, SC: York Technical College
  3. Wicander, Reed, and James S. Monroe. Historical Geology: Evolution of Earth and Life through Time. 6th Edition ed. Belmont, CA: Brooks/Cole, Cengage Learning, 2010.

This WikiPage developed by Richmond Pierce - Fall2011