Types of Rocks

• Rock


  A solid, naturally occurring material made up of minerals or mineral-like matter like shells
• Types of rocks


  • Igneous
  • Sedimentary
  • Metamorphic
• Igneous rocks


  • Formed when magma or molten rock cools
  • Can cool quickly at the surface (extrusive/volcanic) or slowly inside the earth (intrusive/plutonic)
• Igneous rocks


  • Obsidian
  • Granite
  • Basalt
  • Scoria
  • Rhyolite
• Obsidian


  Igneous extrusive/volcanic rock made of quartz, alkali, and feldspar, with a glassy appearance and hardness of 6-7
• Granite


  Igneous intrusive/plutonic rock made of feldspar, quartz, and mica, with medium to coarse grain crystals and hardness of 5-5.5
• Basalt


  Igneous extrusive rock made of plagioclase feldspar and pyroxene, dark and dense with a fine grain and hardness of 5-6
• Scoria


  Igneous volcanic rock made of feldspar, augite, and hornblende, with cavities filled with other minerals
• Rhyolite


  Igneous extrusive rock made of feldspar, quartz, and mica, with a very fine and often porous texture that can float in water
• Sedimentary rocks


  Formed from pre-existing rocks or pieces of once living organisms that accumulate on the Earth's surface or under the ocean
• Types of sedimentary rocks

  • Clastic (formed from fragments of pre-existing rocks)
  • Chemical (formed by precipitation of minerals from water)
  • Organic (formed from the accumulation of plant and animal debris)
• Clastic sedimentary rocks


  Subdivided by dominant particle size: clay, silt, sand, gravel, pebble, boulder
• Shale


  Fine-grained clastic sedimentary rock composed of mud (clay minerals and silt-sized quartz/calcite particles)
• Sandstone


  Common clastic sedimentary rock composed of sand-sized grains of mineral, rock, or organic material, bound by a cementing material
• Conglomerate


  Coarse-grained clastic sedimentary rock composed of pebbles and boulders, with smaller particles filling the spaces between
• Limestone


  Organic sedimentary rock often composed of the skeleton fragments of marine organisms like coral
• Metamorphic rocks


  Formed from existing rocks subjected to extreme heat and pressure, which changes the original structure
• Types of metamorphic rocks

  • Foliated (with crystals in stripes)
  • Non-foliated (without crystals in stripes)
• Slate


  Foliated metamorphic rock with very small minerals, formed from the parent rock shale
• Marble


  Non-foliated metamorphic rock with fine to medium crystals, formed from the parent rock limestone
• Quartzite


  Non-foliated metamorphic rock, formed from the parent rock sandstone
• Gneiss


  Foliated metamorphic rock, formed from the parent rock schist
• Schist


  Foliated metamorphic rock, formed from the parent rock slate