Minerals

• what are the three classifications of rocks?

  igneous, sedimentary and metamorphic
• how do igneous rocks form?

  from the cooling and solidification of molten rock
• what are extrusive rocks?

  igneous rocks formed by volcanism - when magma exits and cools above the earth's surface
• how are sedimentary rocks formed?

  by the hardening and cementation of layers of sediment deposited at the earth's surface
• how are metamorphic rocks formed?

  from pre-existing rocks being transformed under intense heat and pressure in their solid states
• how is marble formed?

  recrystallisation
• what are minerals?

  naturally occurring inorganic crystalline solids
• what does crystalline mean?

  regular internal structures
• what are diagnostic properties?

  characteristic physical properties which allow us to identify which mineral they are
• what do we call the physical properties which allow us to distinguish which mineral is which?

  diagnostic properties
• what do minerals aggregate together to form?

  rock
• does one rock have to contain only one kind of mineral?

  no
• what are the main rock forming minerals known as?

  silicates
• what do silicates contain?

  silicon and oxygen combined with metallic elements
• what process do minerals form by?

  crystallisation
• what is the process of crystallisation?

  the process of forming solid crystals, melt or deposition directly from the gas phase = there is no liquid stage
• how is each silicon organised?

  4 fold coordination to the surrounding oxygen in a regular tetrahedron
• what is the building block of silicate minerals known as?

  the SiO4 silica tetrahedron
• what is the charge on a silica tetrahedron?

  -4
• why is the charge of a silica tetrahedron -4?

  there are four lots of O2- which gives a charge of -8 and one lot of Si4+ which gives a charge of +4, these balance out to give the charge of -4
• what does the charge of -4 mean for the silicate tetrahedron?

  that it is a silicate anion
• name a mineral made from isolated tetrahedrons?

  olivine
• what is olivine made from?

  silica anions and metal cations - usually iron or magnesium
• name a mineral made from single chains of tetrahedra?

  Pyroxene
• how many cleavage planes does pyroxene have?

  two
• name a mineral made from double chained silicates?

  amphibole
• when does amphibole form?

  when every other tetrahedron in a single chain shares its third oxygen ion with an adjoining chain
• name a mineral formed when sheets of tetrahedra form?

  mica and quartz
• when do sheets form?

  when every tetrahedra shares three of its oxygen ions with neighbouring tetrahedrons
• name two common sheet silicates?

  muscovite and biotite
• what are the three cations added to feldspar to solve the charge imbalance?

  K+, Na+ and Ca2+
• what are feldspars containing the K+ cation called?

  K-feldspars or alkali feldspar
• what are feldspar containing N+ or Ca2+ called?

  plagioclase feldspar
• what is mineral polymorphism?

  when we have the same chemical composition, but different physical crystal structures
• give an example of a mineral polymorphism?

  graphite and diamond
• what are both graphite and diamond made from?

  pure carbon
• what are the bonds between sheets called?

  van der Waals bonds
• what is the most common mineral with no cleavage planes?

  quartz
• what is the name for the list which determines which mineral can scratch other minerals?

  Mohs scale of hardness
• what is the softest mineral on Mohs scale of hardness?

  talc