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Fossil stories

Conservation of a Jurassic marine reptile


The jaw unfortunately had begun to suffer from a common occurrence in fossil found in areas with high levels of pyrite known as pyrite decay, however after some work  the ‘toothy’ smile of the Ichthyosaur has been brought back to life in all its glory.

The problem - Pyrite decay

The Ichthyosaur specimen was found in rocks which were Jurassic in age. Geologists describe the surrounding rock as matrix, which in this scenario was a very find clay. The fossil was uncovered nearly 100 years ago where it has been in the collections at Northampton museum and art gallery since its donation. The surrounding rock was deposited during a time in which Northampton was under an ocean. During lithification the process in which sediments like sand becomes compacted into rock, sulphate and iron minerals provided an ideal environment for the formation of pyrite, commonly known as fool’s gold.

Pyrite is unstable at the earth’s surface, reacting with oxygen and water it begins to breakdown. This is commonly known as pyrite disease. During this chemical reaction, moisture in the air reacts to form sulphuric acid. This leads to the breakdown and destruction of fossils and geological samples over the long term. In order to protect against pyrite decay it is recommended to seal any fossils you find on the beach with a sealant, you will find many different examples online to use but a good recommendation would be B-72 Paraloid – a completely reversible resin which prevents pyrite reacting. Alternatively, you can attempt to keep fossils away from moisture in a very dry environment.


To preserve our fossil for future generations it was sent to professional conservationist Nigel Larkin. Using air abrasive pens, tiny precision tools which blast matrix away from the fossil, a thin layer of pyritised matrix was removed from the surface of the fossil. Sodium bicarbonate was used to neutralise the acidity of any sulphuric acid that was present on the surface. After removing all the surface matrix, it was important to ensure that the pyrite inside the fossil jaw would not react again to the environment. As a result, the fossil was submerged in ammonia gas for 36 hours to neutralise the PH of any possible surface acidity. After the conservation of the jaw was finished the fossil was 3D scanned and a 3D model produced which will be useable in future study.

Read more conservation stories

We follow passive conservation measures to care for our collection, essentially ensuring that the spaces in which they are displayed or stored do not cause them to deteriate. Where necessary we make minimal active interventions to care for our collections and prepare objects for display.

Conservation of a cabinet at Abington Park Museum