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     The Earth has melted rock deep inside it.  This is called magma.  If the magma stays underground, cools, and hardens, it is called intrusive igneous rock.  Because it is inside the Earth, it cools slowly so that it makes big crystals. When the magma flows through and around other rocks, it makes veins of rock inside it.
     Extrusive igneous rock is made when magma comes to the Earth’s surface in the form of lava and then cools and hardens.  Lava flows out of volcanoes.  Lava and magma are the same.  They just change the name of the magma when it comes to the surface.  Since it cools quicker, the crystals of surface igneous rock are smaller.
     Some igneous rock is coarse or large grained and some is fine grained.  The kinds of minerals in the rock decide its color.  Silica makes the rock light colored and darker colors have other minerals and no silica in them.  Some usual combinations of minerals that make ores are lead-zinc, zinc-iron-manganese, or iron-titanium.  About 4/5ths of the Earth’s crust is made up of igneous rock.

Igneous rocks

Mt. Rushmore =
igneous rock

Examples of igneous rocks:

	Gneiss
	Granite
	Sand

Examples of minerals found in igneous rocks:

	Alexandrite			Platinum
	Amethyst			Pyrite
	Chalcopyrite			Quartz
	Copper			Ruby
	Diamond			Sapphire
	Galena/Lead			Silver
	Garnet			Sphalerite
	Graphite			Talc
	Hematite			Tin
	Magnetite			Titanium
	Mica			Topaz
		Biotite		Turquoise
		Lepidolite		Uraninite
		Muscovite		Zinc
	Olivine/ Peridot

Citations:

Fuller, Sue.  Rocks & Minerals.  London: Dorling Kindersley, 1995.

Zim, Herbert S.  Rocks and minerals: a guide to familiar minerals, gems, ores and rocks.  New York:  Golden Press, 1957.