Extracting microfossils from flint

Flint meal is a rich source of siliceous microfossils. The material is often packed with sponge spicules, as well as foraminifera and ostracods.

To collect flint meal unweathered, fresh flints recently eroded out of chalk are necessary. Some locations will have a higher concentration of meal bearing flint nodules, but when you are at a chalk location, it is always worth keeping an eye out for the ‘right type’ of flint.

Flint meal bearing flint nodules tend to have a pitted and uneven appearance. When broken, cavities inside the rock can be seen, and in these cavities a powdery chalk like substance can sometimes be found – this is flint meal.

Once you have collected a quantity of this material, place it in acid to remove its calcium carbonate content and then wet sieve it through 2mm, 250 micron and 150 micron sieves.

When dry, you should be able to find many different types of sponge spicules in the residue, together with other types of microfossils. These can then be mounted on microfossil slides available from UKGE, using a 20% PVA in water solution.

Typical flint meal bearing flint - straight out of the chalkTypical flint meal bearing flint – straight out of the chalk.

Split flints containing flint meal
Split flints containing flint meal.

Endecotts Test Sieves Available from UKGE

Microfossil Slides

by Joe Shimmin