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Igneous Rocks

Igneous Rocks. Igneous Rock Formation. Igneous rock: forms when lava or magma cools and minerals crystalize Magma : molten rock below the Earth’s surface Lava : is magma that flows out onto the Earth’s surface The type of igneous rock that forms depends on the composition of the magma.

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Igneous Rocks

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  1. Igneous Rocks

  2. Igneous Rock Formation • Igneous rock: forms when lava or magma cools and minerals crystalize • Magma: molten rock below the Earth’s surface • Lava: is magma that flows out onto the Earth’s surface • The type of igneous rock that forms depends on the composition of the magma. • Of all of the compounds present in magma, silica is the most abundant and has the greatest effect on the magma characteristics

  3. TYPES of MAGMA • Three types of Magma: • 1. Basaltic • 2. Andesitic • 3. Rhyolitic

  4. Classification of Igneous Rocks • Classification of igneous rock is based on mineral composition, crystal size, and texture. • Two Classifications of Igneous Rocks • Intrusive: when magma cools and crystalizes below the Earth’s surface • Extrusive: Magma that cools and crystalizes on Earth’s surface

  5. Classification of Igneous Rocks • Texture: • Size • Shape • Distribution of the crystals or grains that make up the rock • Rhyolite is fine grained while granite is coarse grained • The difference in crystal size is because one is intrusive and the other extrusive Rhyolite Granite Obsidian

  6. Classification of Igneous Rocks • Crystal size and cooling rates • Cools quickly- small crystals • Example: rhyolite- extrusive • Cools slowly- larger crystals • Example: Granite- intrusive

  7. Classification of Igneous Rocks • Rock textures provide information about rock’s formation. • Porphyritic Rocks: large, well formed crystals surrounded by finger grained crystals of the same mineral or different minerals • Vesicular Rocks: Magma contains dissolved gases. If lava is thick enough it traps the gases and holes called vesicles are formed pumice

  8. Igneous Rocks as Resources • Veins: a vein is a distinct sheet-like body of crystalized minerals within a rock. Veins form when mineral are deposited through precipitation. • Pegmatites: Ores of rare elements, such as lithium and beryllium.

  9. Igneous Rocks as Resources • Kimberlites: minerals formed deep in the crust or in the mantle. Can only from under high pressure. • Example: Diamonds • Igneous Rocks in Construction: • Interlocking grain texture makes them strong • Resistant to weather

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