Rock Groups


What is a rock?

  • a coherent, naturally occurring solid
  • consists of an aggregate of minerals or, less commonly, glass



  • a rock holds together
  • rock can form cliffs or be carved into sculptures
  • a pile of unattached mineral grains is not a rock





Naturally occurring:

  • manufactured materials, such as concrete and brick are not rocks




An aggregate of minerals or a mass of glass

  • the vast majority of rocks consist of an aggregate (collection) of many mineral grains and/or crystals stuck or grown together
  • some rocks contain only one mineral
  • some rocks contain several different kinds of minerals
  • a few rock types consist of glass




What holds rock together?

  • natural cement: mineral material the precipitates from water and fills the spaces between grains
  • called clastic rocks:




  • minerals can interlock together like pieces of a jigsaw puzzle
  • called crystalline rocks:





Rock Classification

  • igneous
  • sedimentary
  • metamorphic