igneous rock classification

• Intrusive igneous rocks are formed when molten rocks solidify at depth within the lithosphere and may be revealed by uplift and erosion.
• Fine-grained igneous rocks form with rapid cooling on the earth's surface, with crystals less than 1mm in diameter.
• Igneous rocks can be classified as silicic, intermediate, mafic, or ultra-mafic based on the percentage of silica or mineral composition.
• Igneous rocks are formed from the cooling and solidification of molten lava or magma, and consist of an interlocking mosaic of crystals.
• Crystal size in igneous rocks is determined by the rate of cooling, with slower cooling resulting in larger crystals (intrusive) and faster cooling resulting in smaller crystals (extrusive).
• Medium-grained igneous rocks form with slower cooling of magma at intrusions, taking hundreds of thousands of years, with crystals 1-3mm in diameter.
• Silicic minerals, such as quartz and feldspar, are rich in silica.
• Extrusive igneous rocks are formed when molten rock reaches the earth's surface through a volcano eruption.
• Rapid cooling of erupted lava can result in a glassy texture, such as obsidian, while cooling of lava flowing into the sea can result in pillow lava (glassy on the outside, fine-grained on the inside).
• Coarse-grained igneous rocks form from slow cooling magma chambers deep underground over millions of years, with crystals larger than 3mm in diameter.
• what is the name of the silicic rock with a fine grain and containing quartz, k feldspar, plagioclase feldspar and mica?

  rhyolite
• what is the name of the silicic rock with a course grain?


  granite
• what is the name of the intermediate fine grained rock?

  andesite
• what minerals do mafic rocks conatin?

  olivine, augite, plagioclase feldspar
• what is the name of the rock that contains OAP minerals with a grain size of less that 1mm?

  basalt
• what is name and silica composition of a rock containing OAP minerals with a grain size between 1-3mm?

  dolerite
• what is the coarse grained mafic igneous rock?

  gabbro
• what is the name and silica composition of the rock that contains augite and olivine?

  peridotite and ultra mafic