grommit Posted April 16, 2008 Share Posted April 16, 2008 We found some of our first fossils the other day. Some were nicely presented shells in rock. Others were ammonite sections, about 20-30 degrees of arc of about 1 ft diameter circle. All we can see are the telltale bumps and shape. It almost seems like a rock cast into the proper shape. For all I know, it is a nice piece under 5 mm layer of rock/dirt. How could I start to clean this? Does anybody ever chisel these? Or is soaking / acid baths better? Thanks, Grommit. Link to comment Share on other sites More sharing options...
Guest Nicholas Posted April 16, 2008 Share Posted April 16, 2008 I suggest you post a picture of it to see what we're dealing with. I personally prefer slowly grinding away the rock with a rotary tool such as a dremel. Depending on the type of rock sometimes soaking in just water can soften it and make things a whole bunch easier. I'm new to prepping but we have some pros on the site that may be able to help. Link to comment Share on other sites More sharing options...
ashcraft Posted April 16, 2008 Share Posted April 16, 2008 The type of matrix, and the composition of the fossil are important. If the matrix is limestone, and the fossil is silica, extraction is simplified, versus both limestone. Brent Ashcraft ashcraft, brent allen Link to comment Share on other sites More sharing options...
grommit Posted April 19, 2008 Author Share Posted April 19, 2008 The type of matrix, and the composition of the fossil are important. If the matrix is limestone, and the fossil is silica, extraction is simplified, versus both limestone.Brent Ashcraft The older pictures are posted in the "Help identifying" section, under title that is something like "Newbies first find". The ammonites are what I am really interested in extracting. The older finds appear to be encased in really hard dry mud. We went to my younger sons school today, and pulled out several from the area. The older one found one that has interesting exposed sections, and a large snail (conch?) Pictures from today attached. I'd be happy with any/all advice as to how to start. exposed section nice snail type thing. same as #1 different, but lots of detail Link to comment Share on other sites More sharing options...
Roger Posted April 19, 2008 Share Posted April 19, 2008 Grommit Looks like a nice start. . . Concerning preparation of fossils the first thing I do is wash them with soap and water. I use an old vegetable brush and basically scrub them. Do not use a wire brush as you will scratch them but the stiff fiber brushes won't. For smaller fossils, use an old tooth brush. This washing will eliminat all of the dirt, mud and sometime even loosely attached matrix from the fossil. Once they dry, then you can see what you really have. From an initial observation of your pictures it looks as though you have three ammonites and one gastropod (snail). The gastropod is definately what they call a "steinkern" which mean that there is no shell material left - what you have is a limestone cast of the original shell. Before you get disappointed, there are many formations that ONLY have steinkerns - there was never any shell materail preserved. This does not lessen the value of your fossil nor take away the ability to identify it. Tools for cleaning fossils - first of all remember that softer things will not scratch hard things therefore wood won't scatch stone but metal will. So when getting ready to prep your fossil by removing excess matrix (the rock or material which surrounds the fossil) you need to carefully examine your fossil to see where fossil begins and matrix ends. Some of the tools I use are as follows: Safety glasses - a good pair. You can not blink fast enough to keep stone chips and metal shards out of your eyes therefore USE THE GLASSES. Toothpicks (the big round sturdy ones used to keep sandwiches together) Sewing needles - again not the small ones but the big ones ( they are relatively cheap at the fabric store) Needle vise - it is a small tool in which you can insert a needle and tighten it down. Hand held engraver - these can be a bit more pricey. They have a vibrating tip and the better ones have several power settings that control the speed of vibration. Hand held rotory tool (either airpowered or electric powered) - some one in an above post mentioned a Dremel. Again these are a bit more expensive (especially the air powered ones) but can be used for a lot of thing other than fossil prep - atleast that is how I rationaized my purchase to my wife<grin>). Airscribe (Chicago Pneumatic) - essentially it is a hand held mini jack hammer with interchangable tips. Where the rotory tool spins, this one moves back and forth. Again the better ones have a variable airflow that controls the amount of movement. Cold Chisels - these are used for cleaning large amounts of matrix away from the fossil. Not meant for close up work. DO NOT USE A WOOD CHISEL. They will chip and fling a piece of metal - not a pretty sight!! Small Cold Chisels - these can be used as you get closer to the fossil. A regular hammer and a smaller hammer - not for hitting the fossil but for using with the chisels. Again make sure that you get a well tempered hammer that won't fling shards from the head. A good magnifying light is nice to have as well unless you have great eyesight. I don't, so I have one of those jeweler's lights (magnifying lens encircled by a florescent light) I am sure that I may have forgotten something but these are really basic tools. When you set out to prep your fossil, it is good to have an idea of what the fossil looks like. Sometime if you can identify what fossil you have then you have an idea of how the fossil may be hidden in the matrix. For example your first ammonit picture, the ammonite has nodes but the last picture that ammonite does not. Therefore when prepping the first specimen you should be carefuly when trying to expose the nodes whereas the second specimen you don't have that issue. finally - you need patience. Don't get in a rush - after all the fossil has been there for millions of years (or 6000 years depending on your religious orientation) and you can take your time. I am sure that there are many more skilled preparators on this forum that will also give you ideas. Listen and learn from all of them and don't be afraid to stop and ask questions if you are uncertain how to proceed. Good luck Roger Link to comment Share on other sites More sharing options...
grommit Posted April 19, 2008 Author Share Posted April 19, 2008 Wow. Thanks. Now my kids are scrubbing away with toothbrushes. Are ammonites ever just steinkerns? They are scrubbing away at some of the crummier specimens that definitely show real fossil. Unfortunately, some of the larger ones just have the shape, but we are hoping the real stuff is underneath. I'll go with the millions of years, but when I take them to work, they will be caveman food / pets to some. My wife bought lots of the tools you mentioned years back for reasons I still haven't figured out. Maybe she had good foresight. Link to comment Share on other sites More sharing options...
Roger Posted April 19, 2008 Share Posted April 19, 2008 Wow. Thanks. Now my kids are scrubbing away with toothbrushes. Grommit <<Are ammonites ever just steinkerns?>> yes - generally they are always steinkerns (caveat - depending on the geologic formation collected from). If they have shell material if will be almost like a mother of pearl. . . <<Unfortunately, some of the larger ones just have the shape, but we are hoping the real stuff is underneath.>> The last ammonite you pictured is already showing it's suture lines therefore there is nothing but more rock beneath. However it is a nice specimen. The reason nothing more will be beneath is that the process of fossilization is similar to pouring concrete (hang with me here the analogy is ok but obviously weak in areas <grin>). Think about putting a bone in the middle of a concrete pour and then continuing to pour concrete. It doesn't leave a hump where the bone is because the depth of the concrete on either side eventually swallows and covers the whole bone and forms a flat top as the concrete settles. Therefore it is very seldom that a fossil will have an outer shell of matrix that mimics the shape of the fossil. Continuing the analogy - after the concrete hardens and dries, 20 years later the concrete is torn up. When they come to the area where the bone is located the concrete will probably break along the outlines of the bone since the bone was a weak spot (it wasn't the same material therfore created a weak spot). When it breaks apart there will be a cast of the bone in the concrete and perahps the bone itself which acted like a mold. Often with ammonites, the ammonite will act as a mold and make a cast of itself in the matrix layer. Sometimes when they split apart (like the bone a fossil is generally a weak point in the overall matrix) you'll end up with a cast and a mold. Now you say well then why wasn't the ammonite's shell preserved like the bone was? This is where the analogy breaks down. When we are talking about fossilization, we are talking about a long time (millions of years) for the matrix to lithify and become stone. As this is happening, other chemical actions are occurring in the matrix and the shell material of the ammonite is being either replaced or eaten away. If it is the latter, then it is being replaced very slowing by matrix - so slowly that it maintain the same shape and outlines - even down to preserving the sutures. If it is replaced by another mineral, then you have a shell but not the original shell material. For a better explanation, I suggest that you and the kids look up "fossilization" on the net. . . it will give you a better understanding of what I am trying to protray. <<My wife bought lots of the tools you mentioned years back for reasons I still haven't figured out.>> She is a very wise woman - obviously one well worth keeping<grin>!! Many of the tools I mentioned are used a lot in arts and crafts and other hobbies. btw - since most of your fossils are limestone - acid won't work!!! It'll desolve the limestone and kill the detail. Roger Link to comment Share on other sites More sharing options...
grommit Posted April 19, 2008 Author Share Posted April 19, 2008 Thanks for the long and informative reply. I don't want to belabor the point, but I am confused on one issue. The last ammonite is showing sutures, so it has nothing left to dig out. Scrub it up, then leave it alone. The gastropod has nothing more worth doing, except scrubbing. The first ammonite has a definite change in texture between the matrix and the fossil proper. I guess this is still rock, just differently mineralized. This can be seen in the 3rd picture. Is that still called a steinkern? Or does that only apply to things where the matrix and the fossil are the same material? I'm guessing the difference is whether the actual shell is still there in near original form, or whether it has mineralized. I'll google fossilization and steinkern. Link to comment Share on other sites More sharing options...
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