The London clay has 3 main types of fossil preservation, carbonation, pyritization and preserved in phosphatic nodules. On this page I will highlight some of the methods in which to best preserve and prepare these types of fossils. 

Pyritization is a common way many fossils are preserved in the London Clay. Pyritization often preserves the fossil wood, bivalves and other types of shell, starfish, crinoid and insect. Fossil wood and shells preserved in pyrite are very common in the London clay while starfish and crinoid are very rare. Insect fossils are extremely rare in the London clay and should be reported if found. 

These pyrite fossils are very unstable and will decay quickly if not treated properly. This is because of the rapid oxidation of Iron Sulphide. To slow down this process you can put the pyrite fossils in a dry container with silica gel to absorb water moisture. Other products such as pyrite stop (https://www.zoicpalaeotech.co.uk/products/pyrite-stop) can be quite effective. 

In the case of very important fossils such as insects, Ammonium gas can be used in a sealed container as this will prevent the decay of the pyrite. However, this should only be done by a professional as Ammonium is a toxic gas and will cause extreme respiratory distress.

To learn more about how to stop the decay of pyrite check: https://www.zoicpalaeotech.co.uk/pages/pyritefossils 

When the fossils are in a phosphatic nodules they are usually in a stable condition but often requires preparation to reveal the fossil. This nodule will often harden the closer to the centre you get. Some of the softer nodules can be prepped with a brush and water with repeated brushing, however often the fossils will require a much stronger tool. 

There are 2 types of these stronger tools, Manual tools, and Machine tools.

Manual tools include scalpels to scrape away the rock, this is quite good as it is low cost for the tools are provides a lot of control over the fossil preventing damage. However manual tools are very time consuming to use and not suitable for bulk matrix removal. 

Machine tools include air abrasives and air pens, these are often very expensive to set up and requires much more safety features. However, these are much faster than any manual tool and can provide easy preparation of the fossils. 

To learn more about air abrasives check out: https://www.zoicpalaeotech.co.uk/pages/all-about-air-abrasives  

To learn more about air pens check out: https://www.zoicpalaeotech.co.uk/pages/how-to-choose-an-air-pen 

On certain London Clay Rocks, Acid preparation can work such as with cement stones and septaria that can be partially acid treated due to the composition as they contain a percentage of limestone and calcite. The 6 or 7% formic acid is best used for bones. It can be quite difficult to get the correct percentages and to acid prep correctly. (Thanks to Dave Savage for helping me with the acid information)

WHEN USING ANY TOOLS PLEASE CHECK THE SAFETY OF THE OPERATING TOOLS

Carbonation is how the fossilised wood on the London Clay is preserved. The teredo wood is often stable and does not need any stabilisation, the best way to prepare teredo wood is via polishing and slicing. The other type of carbonized wood is black in colour and is extremely unstable, there is very little which can be done to preserve this type of fossil, however product mentioned in the Pyrite section might have some effect.