Rocks and Minerals

• Rock - a naturally formed, non-living earth material.
• Rocks are made of collections of mineral grains that are held together in a firm, solid mass.
• Bed rock - a mass of consolidated rock that has not weathered.
• Three Types of Rocks

  • Igneous
  • Sedimentary
  • Metamorphic
• Igneous Rock - molten rock materials cools and solidifies form.
• Magma - molten rock matter below Earth's surface
• Lava - magma that erupts onto Earth's surface
• Chemical composition of the magma and the rate at which it cools determine what rock forms as the minerals cool and crystallize.
• Texture - can be classified in terms of their size and mineral composition.
• Felsic - light colored, light-weight minerals especially silicon and aluminum
• Granite -coarse-grained intrusive rock
• Rhyolite - fine-grained extrusive rock
• Mafic - lower in silica and rich in heavy minerals
• Basalt - dark colored fine-grained extrusive rock
• Gabbro - coarse-grained intrusive rock that cools at depth
• Intrusive/Plutonic

  • Form within the Earth
  • Slow cooling
  • Interlocking large crystals
  • Example: granite, gabbro
• Extrusive/Volcanic

  • Form on the surface of the Earth as a result of volcanic eruption
  • Rapid cooling
  • Glassy and/or fine-grained texture
  • Example: basalt, obsidian
• Vesicular - has holes which was caused by rapid air cooling and causes air bubbles to be trapped inside the rock.
• Sedimentary - formed by the compaction and cementing together of sediments, broken pieces of rock-like gravel, sand, silt, or clay (lithification)
• Three major categories of sedimentary rocks: clastic, organic, and chemical precipitate.
• Lithification - the process that converts sediments into solid.
• Organic Sedimentary Rock - lithify from remains of organisms, both plants and animals (ex. coal)
• Chemical Precipitates - the solid materials left behind after a liquid evaporates.
• Clastic Sedimentary Rock - form from fragments of preexisting rocks, shells, or bones.
• Conglomerate - lithified mass of cemented roughly rounded pebbles, cobbles, and boulders and may have clay, silt, or a filming in spaces between those large particles.
• Breccia - composed of lithified fragments that are angular rather than rounded.
• Sandstone - consist of cemented sand-size particles, most commonly grains of quartz, has granular, porous, resistant to weathering.
• Siltstone - individual siltsized particles are not easily visible.
• Shale - compaction of finely-grained sediments.
• Stratification - layering in rocks
• Bedding Plane - boundary between sedimentary layers that represent depositional events.
• Cross Bedding - a pattern of thin sediment layers that accumulate at an angle to the remain strata.
• Origin of Sediment - produced by weathering and erosion or by precipitation from solution.
• Weathering - chemical and mechanical breakdown of rocks
• Erosion - processes that get the weathered material moving
• Metamorphic Rock - when the minerals in an existing rock are

  changed by heat or pressure within the Earth
• 2 types of metamorphic rock - foliated (presence) and non-foliated (absence)
• Types of Formation

  1. Contact Metamorphism
  2. Regional Metamorphism
• Contact Metamorphism – when a rock is

  exposed to extreme heat and pressure within

  the Earth but does not melt, the rock become

  metamorphosed
• Regional Metamorphism – occurs commonly

  when crustal rocks are subjected to great

  pressures by tectonic processes or deep burial, or where rising magma generates heat and

  pressure, to re-precipitate perpendicular to the

  applied stress, forming platy surfaces or wavy

  bands.