Beginners Guide to Air Preparation of Fossils

Though by no means an expert,to get used to managing the website I thought I would try and share a little knowledge on how to prepare a rough ammonite nodule from beach found.

I have taken an example of a small iron stone concretion typical of those to be found on the Yorkshire coast. Nearly all of these have an ammonite inside,usually a Dactylioceras commune.

Rough beach preparation with a hammer blow is usually done to save carrying back useless nodules.

Many break through the ammonite with the first hammer blow,so if you can see a really large edge of ammonite I would advise against beach preparation,and go straight to the air pen.

Image 1    below       Rough Iron Stone Nodule


The iron coloured outer layer chips away very easily

So,the next step is to crack the nodule open. Watch your eyes!! and watch your hands ,though with some care these nodules tend to spit pretty easily.You must wear eye protection,a decent hammer helps,and gloves are a must.

The result hopefully will be a popped out ammonite as in the image below:

Image 2  below     Popped out ammonite :


 A word about preparation cabinets. Stone dust  kills!! I made a small cabinet that extracts all the dust away to the outside.It is advisable to wear a suitable dust mask aswell. You only get one set of lungs!!!!.

It is air tight and has a small kitchen extraction fan in the rear,venting to the outside.

Image 3     Home made extraction cabinet :

I use a KM airpen. This runs off an air compressor.

Image 4      Air compressor  200litre receiver tank:

The airpen is a fine chisel  that vibrates up and down chipping off the rock matrix. The challenge to expose as much of the fossil without damaging it!

Image 5      Airpen :

An air tool to reduce the matrix and expose more of the fossil.This tool was supplied by Ken Mannion.

My preference is for an equal area of matrix all around the fossil,this may be flat,or in some cases dished.

Once roughed out,I use a dremmal to grind the matrix smooth.

Here is the fossil after penning,but before grinding the matrix:

Image 6      Fossil after penning:

At this stage,grinding of the matrix is done with the dremal. This can generate a lot of dust so definitely done in the dust extraction cabinet.

After grinding with the dremmal my preference is to sand the matrix down with fine wet and dry sand paper.I then dry the fossil and apply a layer of furniture wax or fossil varnish to the fossil itself.This masks minor 'dings',  the trademark of beginner preparators!

Here's the finished ammonite.A thin layer of furniture polish has beenapplied.

Image 7     Finished ammonite    Dactylioceras  commune