MadSci Network: Earth Sciences

Re: What are the steps to removing a fossil from a rock?

Date: Tue May 9 08:21:41 2000
Posted By: David Kopaska-Merkel, Staff Hydrogeology Division, Geological Survey of Alabama
Area of science: Earth Sciences
ID: 956886692.Es


The most important thing to remember about cleaning fossils is that most of 
the things you can try are potentially dangerous, so always seek help from 
an adult first (I mean someone who is right there to help you like your 
parent or teacher -- asking me over the internet doesn't count for safety 
purposes!). The second most important thing to remember is that most 
fossils are fragile, so be gentle with them.

There is not one set of steps needed to remove fossils from rock, because 
there are many different kinds of rock, and many different kinds of fossil 
preservation. Each presents its own problems and opportunities for 
cleaning. In general, it is not easy to clean a fossil, though some kinds 
are easier to deal with than others. If you have a particular fossil you 
are trying to "prepare" (that's what it's called when one removes or cleans 
a fossil so that it can be seen better) then you should tell me what it is 
like and maybe I can help you more. For now, I'll give you some general 
information that should help. 

Some fossils cannot be removed from the rock. Most of these are trace 
fossils, like footprints, and they are simply impressions in the rock 
itself; they are not made out of different material. 

Most plant fossils are carbon films that are very fragile, and they are 
usually preserved in shale. Any preparation beyond splitting the rock to 
reveal the fossil could easily damage the fossil. However, it is possible 
sometimes to use a sharp blade to pry off thin layers of rock that cover 
parts of the plant fossils. DO THIS ONLY WITH ADULT SUPERVISION!

Fossils in soft sandstone or soft shale are the easiest to prepare. Some 
fossils, like shark teeth, tend to pop right out of the rock, especially if 
they are preserved in soft, poorly cemented sandstone. Fossils in soft 
sandstone can often be cleaned with a small brush. A used toothbrush works 
well. Sometimes soaking soft shale in water, or water plus detergent, will 
loosen the fossils, or even make the shale disintegrate without harming the 

Most fossils are sea shells in limestone, and they are not easy to prepare. 
If the fossils are made of silica (what glass is made of), then the 
limestone could be dissolved in acid because the silica fossil will not 
dissolve. THIS IS DANGEROUS! If you know a chemist, that person can help 
you do this safely. Otherwise, don't try it!! 

Most sea shells are made of calcium carbonate, which is the same thing 
limestone is made of. However, the shells are often just a little bit 
harder than the surrounding rock, because they have a regular crystal 
structure, and there is a surface of weakness separating the fossil from 
the rock. The best way to clean this kind of fossil is using a vibrotool, a 
tool with a sharp point that vibrates, or a sharp metal pick, like the kind 
dentists use (dentists will sometimes give you old ones that are only a 
little broken). This is not very easy, and you can hurt yourself, so once 

Most of the fossils in Ohio are probably calcium carbonate shells in 
limestone, and so it will not be very easy to remove them from the rock. If 
there are pieces of rock covering parts of the fossils, sometimes you can 
remove the extra rock with hammer and chisel. There is a strong chance you 
will smash the fossil if you try this, so don't try it on your prettiest 

Here are some good general rules about cleaning fossils:

1. Try any method on ugly specimens first.
2. Always wear safety goggles.
3. Consult an adult before you try anything.

Here is a list of publications you can use to get more information:

Resources for the Study and Preparation of Fossils
	The following brief list of publications contains a few general 
references for teachers who may not have their own resources on this topic; 
no endorsement of the following books is intended.

Lichter, Gerhard, 1993, Fossil collector's handbook:  New York, Sterling 
Publishing, 160 p.
MacFall, R. P., and Wollin, J. C., 1972, Fossils for amateurs:  New York, 
Van Nostrand Reinhold, 341 p.
The Nature Co., 1995, Dinosaurs:  New York, Time-Life Books, 64 p.
Psihoyos, Louie, 1994, Hunting dinosaurs:  New York, Random House, 267 p.
Reader's Digest, 1995, A look inside dinosaurs:  Westport, Connecticut, 
Joshua Morris Publishing, 19 p.
Whitaker, G. O., and Meyers, Joan, 1965, Dinosaur hunt:  New York, 
Harcourt, Brace, and World, 94 p.

I hope this information helps.

David Kopaska-Merkel
Geological Survey of Alabama
PO Box 869999
Tuscaloosa  AL 35486-6999
(205) 349-2852
FAX (205) 349-2861
web site:

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