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How Fossils are Prepared


How Fossils are Prepared
Photo © Steve Cole / Getty.
Fossil preparation is a process by which paleontologists (or fossil preparators) remove the sediment or rock—also referred to as the matrix—surrounding a fossil to reveal the details of the preserved lifeform. Proper fossil preparation best reveals any information a fossil can provide while poor fossil prepration can result in the loss of that information. Depending on the type of fossil and the condition it is in when it is discovered, its preparation can be quite simple or may require considerable knowledge, skill, and patience. The actuall cleaning of a fossil to reveal the specimen is just one in a series of tasks that are carried out to interpret a fossil.

The basic steps in fossil preparation include:

  • Documenting the fossil
  • Collecting the fossil
  • Preparing the fossil

Documenting the Fossil

Fossil preparation begins in the field as soon as a fossil is discovered. There is great deal of valuable information that can be gained from an in-situ fossil. The rock or sediments in which the fossil has been preserved can lend clues about the fossil's age and how it might have formed. If there are other fossils located in the rocks and sediments close to the fossil, they can provide context—hints of prehistoric animal communities or evidence of ancient climate conditions. Thus, the first step is carefully documenting details about the specimen itself, its geographic location, and the geological setting in which it was found. Specimens are assigned unique numbers that are used to cross-reference the fossil specimen with all of the data that have been collected for it.

Collecting the Fossil

The next step in preparing a fossil is collecting the fossil. In some situations a fossil may be sitting loose on the surface of the ground and can simply be picked up with little effort at all. In other situations, the fossil may be only partially exposed or may be extremely fragile. These situations may require more skilled methods of freeing the fossil from the surrounding substrate.

One such process is called field jacketing. Field jacketing involves carefully excavating around the fossil to determine its extent. Then the fossil is covered in a plaster and burlap cast. This cast supports the fossil and protects it while it is cut out of the surrounding rock and transported to the laboratory where more delicate cleaning of the fossil can take place. If a fossil is extremely fragile, the preparer may coat it with consolideants (resins that strengthen the fossil).

Preparing the Fossil

Once the fossil has been collected from the field, it is often taken back to a laboratory where a preparator removes the sediment or rock that encases the fossil remains. To do this, the preparator uses a wide range of tools depending on the nature of the matrix in which the fossil is held. Such tools might include brushes, air abrasive devices, mini air hammers, electric etchers, pneumatic rotary grinders. If the fossil is unstable and requires consolidants and adhesives to prevent it from degrading, these are applied in moderation. The preferred resins used today soak into the fossil and give it support from the inside out (rather than simply coating the outside surface of the fossil as older consolidants did, leaving the interior structure weak and vulnerable).


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