ROCKS+and+how+to+identify+them

ROCKS+and+how+to+identify+them - ROCKS . and how to...

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ROCKS . .. and how to identify them ROCKS . .. and how to identify them A tutorial program offered to you by the Applied Science Department of Glendale Community College presented by: Susan Celestian – Curator of the Arizona Mining and Mineral Museum Stan Celestian – Photographer and Instructor © copyright 2002
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THE ROCK CYCLE THE ROCK CYCLE Rocks are naturally occurring combinations or coherent aggregates of minerals, fossils or other hard materials. They are classified by the way in which they form. The three rock types are: igneous, sedimentary and metamorphic. All rocks on Earth are locked into a system of cycling and re-cycling known as the ROCK CYCLE .
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METAMORPHIC METAMORPHIC SEDIMENTARY IGNEOUS IGNEOUS m el t i n g h ea , pr es s u r e, on w e a po o n l f c weathering, transportation, lithification heat, pressure, ions THE ROCK CYCLE THE ROCK CYCLE
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IGNEOUS ROCKS IGNEOUS ROCKS IGNEOUS ROCKS are “born of fire”. In other words, they were once molten and upon cooling, the magma (molten rock) crystallized into solid rock. Igneous rocks may form deep inside the Earth or at the Earth’s surface when a volcano erupts. magma conduit Anat omy of a Vol cano vent lava l a n d s u r f c e
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IGNEOUS ROCKS IGNEOUS ROCKS Slow cooling deep beneath the Earth’s surface allows crystals to grow to large size (1/8” or more). These crystals are easily visible and distinguish this group of igneous rocks as INTRUSIVE . Rapid cooling near or at the Earth’s surface, produces many small crystals that are not readily seen by the unaided eye. This group of igneous rocks is called EXTRUSIVE and are typically volcanic in origin. Cooling may be so rapid that crystals do not have a chance to form and instead a glass is produced.
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LIGHT COLORED Felsic INTERMEDIATE COLORED DARK COLORED Mafic VERY DARK COLORED Ultramafic COARSE- GRAINED (You can see different minerals) GRANITE: Can see crystals. Usually gray or pink. Can see quartz - gray, glassy grains. Can see feldspar - pink, buff, or white. DIORITE : Can see crystals with somewhat more light colored feldspar grains than dark colored minerals. A mix of light and dark but with no quartz. Salt . GABBRO : Can see crystals — lots of flat shiny cleavage surfaces. Usually black to greenish black. FINE- GRAINED (You can NOT see crystals, for the most part) RHYOLITE : Usually gray, pink, pastel. Might see small clear, rectangular crystals. Sometimes banded. ANDESITE : Light to dark gray. Normally has small black crystals BASALT : Usually black or rust red. May have some or lots of gas bubble holes, some holes may be filled. May see small green grains. GLASSY
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ROCKS+and+how+to+identify+them - ROCKS . and how to...

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