Fossil Preparation Requires Care and Precision

Hobbyists and paleontologists prepare fossil specimens for research or exhibition by removing the surrounding rocky material (matrix) and cleaning the fossil. However, fossil preparation must be done carefully with the best available methods to produce excellent results.

Revealing Fossils

Fossils often come out of the ground embedded in matrix, delivered to the institution in a field jacket. Thus, they require preparation to fully reveal the fossil to be studied or exhibited. Poor preparation can result in permanent damage to a fossil or leave it unusable.

Thus, preparation should only be performed by specialists who understand the specimens, the materials to be removed and preserved, and the techniques available to accomplish those tasks.

Fossil Preparation Techniques

Fossil preparation involves three primary techniques, chemical, mechanical, and non-invasive. With chemical preparation, you apply specific compounds, like hydrochloric acid, to the specimen to dissolve the matrix around the fossil. Mechanical preparation uses physical force to remove the matrix with various methods and tools. Non-invasive preparation involves the use of non-destructive technology to reveal information about the fossil.

Chemical Preparation

Small shelly or other phosphatic fossils can be extracted from a carbonate matrix using hydrochloric acid or acetic acid. Organic fossils can also be extracted from silicate rocks using hydrofluoric acid. Or, a cellulose nitrate film which adheres to the organic component may be applied, allowing the rock to be dissolved around it.

Mechanical Preparation

  • Airscribes – Airscribes are pneumatic striking tools, like miniature jackhammers that force small flakes of matrix away from the fossilized bone. Airscribes vary in size, allowing for granular removal or for the large-scale removal of harder material.
  • Rotary Tools – To delicately remove material too hard or brittle to eliminate with a scribe, rotary tools can be used. Rotary tools may also be useful in the prep lab for trimming jackets and other destructive processes.
  • Micro-Abrasive Blasting – Acting as a smaller and much more precise sand blaster, micro-abrasive blasting machines deliver a fine stream of abrasive material, such as sodium bicarbonate to precisely remove the matrix surrounding the fossil.

In addition, well-prepared specimens often retain a layer of fine dust. This troublesome layer is most simply removed by micro-abrasive blasting. Operators often use aluminum oxide powder to cut the matrix. But this must be done carefully to avoid damaging the fossil. For best results, they direct the nozzle at an angle to the bone.

Fossil Preparation

Advantages of Micro-Abrasive Blasting for Fossil Preparation

Abrasive blasting became popular with paleontologists in the 1960’s. It can potentially reveal fine details that may not be visible after using other mechanical techniques. Some in the field also find it to be faster than other techniques.

The abrasive blasting technique works best when the matrix is softer than the surrounding fossil and where poor separation between the fossil and the matrix occurs. Experienced operators often use blasting to remove the last layer of matrix from a specimen.

You may also consider it for use on delicate fossils. And, with an abundance of caution, you may want to use abrasive blasting when you fear that vibrations from other mechanical tools may harm the specimen.

Professional Endorsement

The proof of the micro-abrasive blasting technique for fossil preparation is in its use. So, consider that prominent paleontologist, Alan Langerheinich, only uses Airbrasive® blasting equipment. He has found that Airbrasive machines outperform the other micro-abrasive blasting brands and models on the market.

For example, in the preparation of a Trilobite specimen, intricate work is required to remove the matrix around free-standing spines and the compound eyes. Success requires very precise powder flow control. Using a vibratory powder feed system, such as that on the Airbrasive Model K, the required precision is achieved.