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Igneous Rocks . Igneous rock definition . Rocks formed by the cooling and solidifying of molten materials. Igneous rocks can form beneath the Earth’s surface from magma , these are intrusive igneous rocks Or on the earths surface from lava , these are extrusive igneous rocks.
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Igneous rock definition • Rocks formed by the cooling and solidifying of molten materials. Igneous rocks can form beneaththe Earth’s surface from magma, these are intrusive igneous rocks • Or on the earths surface from lava, these are extrusive igneous rocks
Igneous Rock characteristics • Texture: Very Course, Course, Fine, Glassy, Vesicular and non-vesicular • Color: Light or Dark • Density: High or Low • Composition: Felsic Al, Si or Mafic Fe, Mg • If a Rock is Dark in color it will also have a Mafic composition and a High density. • If a rock is Light in color it will also have a felsiccompostion and a Low density
Very Course to Course Texture Course Crystal size 1mm to 10mm Very Course Crystal size 10mm or larger
Fine Texture Fine Crystal size Less then 1 mm
Glassy Texture Crystal size Non-crystalline Meaning no visible crystals
Vesicular Texture Visible gas pockets
Mafic Intrusive rockGabbro Large crystals Dark in color
Mafic extrusive rockBasalt small crystals Dark in color
Felsic Intrusive rock Granite Large crystals Light in color
Felsic extrusive rockRhyolite Small crystals Light in color