Types of Rocks

• Igneous


  Formed from magma within the earth at high temps

  Magma cools to produce rocks with a crystalline structure

  Have no preferred allignment
• Intrusive Igneous


  Also called Plutonic Rocks; different crystal sizes formed at different depths
• Extrusive Igneous


  Erupted as lava or fragments from a volcano; gives a fine crystal size
• Sedimentory


  Formed at relatively low pressure and temp. at shallow depths below the Earths Surface

  Contain Fossils

  Made from weathering and erosion

  Made of clasts and held together by cement
• Metamorphic


  Rocks subjected to increased temp. OR increased Temp and Pressure

  Causes texture and mineral composition to change

  Minerals Recrystalise and often show preferred alignment

  Alignment creates Foliation
• Rock Texture


  Refers to what it is made of and how it looks - not just how it feels