Thursday, 22 November 2012

Crushing rock – part 1

For the last few weeks I have been preparing my rock samples for future analytical work. There are over 400 samples to be washed and prepared, first removing seaweed and barnacles, then cutting the rock down to pieces ready for further analysis. This involves a low of rock sawing and crushing using various machines, a messy job but it is very interesting as you get to see ‘inside the rock’. In this blog I will go through the first few stages of rock crushing.

Why is crushing rocks useful for scientific research?

Surprisingly, there is actually a lot you can learn from sawing and crushing rocks. I am preparing the samples for five different types of analysis:
  1. Large samples with a complex interior structure are sawed ready to be polished (see blog 8).
  2. Small pieces of rock are prepared for thin sections. Thin sections can tell us about the rock composition, structure and texture, helping us understand how they formed.
  3. Small pieces of rock containing organic material are selected for study at the University of Southampton for their palynomorph content such as plant spores.
  4. Small pieces of rock containing microfossils are retained for future sieving (see blog 3).
  5. Crushed rock powder will be analysed for carbon isotopes and carbon content. Samples containing plant material or a high organic content are selected.
Crushing Rock in pictures

Step 1
Slice off the weathered surface of the rock using a rock saw to expose fresh rock underneath. In the pictures below you can see me sawing a conglomerate. This saw is also used for cutting small pieces of rock for thin section.

Step 2
Use the rock splitter to break the sample up into smaller pieces. By splitting rocks along their bedding planes you can reveal hidden structures and fossils. Here I have split a siltstone rock and a fossilised burrow along the bedding surface was revealed. The rock pieces produced can be put aside for sieving and palynology, or crushed further for geochemical analysis.

Step 3
By using a machine called a fly press the rock pieces are crushed into millimetre sized fragments.

In the next post I will detail the next steps in the rock crushing process.

Until next time

Our Local Geology Society

This is a very short blog to promote our local amateur geology group in Leicester, the Leicester Literary and Philosophical Society, Section C, Geology, established in 1849. The society holds research talks, seminars and summer fieldtrips, attended by geology amateurs and professionals of all ages, you can find out more information here. I have been a member for many years and now I am on the committee as the Department of Geology staff representative, so yes I am biased towards the society! Through this group I have learned a lot about our local geology, such as building stones, local fossil sites and about Charnia and other Ediacaran fossils from Charnwood Forest in Leicestershire, which are the oldest fossils in the UK. If you would like to get involved with a local society, check out the links page on the Charnia website (

On Monday last week we welcomed our Tweed leader Professor Jenny Clack to give a talk at the parent body meeting of the Lit and Phil. This was well attended and gave an overview of the entire project, plus some information on new tetrapod fossil finds. Before the talk I put on a small fossil and rock display in the geology department and Jenny also brought in some tetrapod and rhizodont (fish) fossil specimens. My favourite specimens were the tetrapod toe bones which were very cute!

Fossil display in the Sylvester Bradley Museum in the Department of Geology, Leicester. Sorry about the blurry photo! We had sedimentary rock specimens, thin sections, microfossils and some large tetrapod and fish bones. Staff, students and members of the Lit and Phil Geology society came to the display.

Next week TWEed project partner Dr Gregory Edgecombe from the Natural History Museum will be talking about his research on a new Burgess Shale-type biota from the early Cambrian of Australia. See the Charnia website for more details.

Until next time