mineral structures - the better one

• island silicate

  • olivine
  • iron and magnesium bond to the 4 spare bonds on the silicon tetrahedra
  • strong covalent bonds - fractures, and high hardness and density
• single chains - pyroxenes

  • formed in the abscence of iron and magnesium
  • silicon tetrahedron bond with atoms like oxygen
  • each tetrahedra share 2 oxygen atoms - bridging oxygen
  • chains are joined by ionic bonds - cleavage develops along theses lines
  • augite
• double chain inosilicates - amphiboles

  • single chains link to form double chains
  • even less available bonds for metallic elements
  • hornblende
  • joined by ionic bonds - cleavage develops along these lines
  • lower hardness and density than island silicates
• sheet silicates

  • double chains link to make a 2-dimensional lattice - a sheet of strongly bonded hexagons
  • sheets held by ionic bonds - cleavage
  • low hardness and density
  • mica
• framework silicates

  • oxygens bonds to each of the four bonds on the silicate tetrahedra
  • 3-dimensional framework - sheets upon sheets
  • covalent bonds - fracture not cleavage
  • high hardness
  • no metal ions so low density
  • quartz