| MadSci Network: Earth Sciences |
Ashley: 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 fossils. 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 again: DO THIS ONLY WITH ADULT SUPERVISION. 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 specimens. 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: www.gsa.state.al.us
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