• Question: what is you favourite rock

    Asked by KaiF to Anna, James, Joe, Leonie, Olivia on 12 Mar 2015. This question was also asked by MLG sloth.
    • Photo: James Pope

      James Pope answered on 12 Mar 2015:

      Hi KaiF,

      AWESOME QUESTION! As someone who started out as a geologist I love a wide range of rocks, but I guess my all time favourite is Sandstone.

      Sandstone is a sedimentary rock which means it is laid down by layers of sediment lying on top of each other which eventually get stuck together and compressed to form a rock.

      The reason I like sandstone the most is that we can tell from sandstone so much about the climate when the sandstone was laid down. Sandstone comes in two types, aeolian (wind blown) and fluvial (water moved). If it is fluvial, we know we had rivers and the size of the sand grains tells us how much water we had, whether it was a big Amazon type river or a small river that dried up in summer. If it is Aeolian, we know we had desert. In Scotland, the “Old Red Sandstones” are 400 million years old and they tell us Scotland was covered by a huge desert at that time. We can even see the shape of sand dunes in the way the sandstone is formed so we can even work out where the wind was coming from at that time.

      Finally, sandstones are great for building and are an important part of the construction of lots of famous and old buildings here in the UK.

    • Photo: Leonie Oostwoud Wijdenes

      Leonie Oostwoud Wijdenes answered on 12 Mar 2015:

      Mine is Blue Apatite because I love the colour

    • Photo: Joe Spencer

      Joe Spencer answered on 12 Mar 2015:

      My favourite is a rock, i think.
      Calcite, because it’s birefringent and looks different depending what angle you look at it, it has cool applications in lasers and optics as well.

    • Photo: Olivia Lynes

      Olivia Lynes answered on 16 Mar 2015:

      For no particular scientific reason- I really like opals! Not really a rock but something that forms on a rock.

Comments

  • Photo: James

    James commented on :

    Sadly Joe (and Leonie), neither of those are rocks, but are minerals. They form as crystals only of themselves. Some minerals, such as Quartz do form rocks (Quartzite) through metamorphic processes, but I can’t find any rocks that form from your minerals.

    Sorry guys!

  • Photo: Joe

    Joe commented on :

    I did know that and was going to mention it, just thought minerals could count in this question.
    Then If it’s a rock.. I’ll go with obsidian.

  • Photo: Leonie

    Leonie commented on :

    This was the most pretty one I could find when I googeled ‘blue rock’. Any suggestions on real rocks that are blue James?

  • Photo: James

    James commented on :

    Leonie, the answer is Blue schist, a metamorphic rock that commonly forms in and around subduction zones as sea bed is dragged under continental crust. The blue when it occurs the rock being metamorphosed has a high concentration of an amphibole mineral called glaucophane. Normally schists are a grey colour.

    It can also occur in slate, the Blue Mines in France an example of slate with this colour.

  • Photo: Leonie

    Leonie commented on :

    Thanks James, I go with blue schist then!