PA Fossil Finder Posted June 23, 2015 Share Posted June 23, 2015 I recently visited several fossil sites in PA, one of which was Ordovician in age and full of hard limestone. The weathered outside of the limestone is tan colored, and can be removed with diligent scrubbing (I used an old toothbrush). The unweathered limestone, however, is very hard and dark gray. That day, I found many chunks of rock with small Cryptolithus heads poking out of the stone, and one half-complete trilobite. How could I prep these trilobites out of the limestone? I have and air compressor, should I buy and air scribe or something similar? Stephen Link to comment Share on other sites More sharing options...
Fossildude19 Posted June 23, 2015 Share Posted June 23, 2015 (edited) Hello, and welcome to the Forum. These would be more easily prepared mechanically - either by an Air scribe, which is like a mini jackhammer, or by an air abrasive unit. Search the forum for these terms, and you will find lots of entries in the Fossil Prep section. Getting into this can be a bit expensive. To do it manually, you would need dental picks and /or a pin vise/pocket scribe. Some people have success using electric rotary or vibratory engravers. Along the same lines, you could use an air powered pencil grinder in the same manner. You could also try some white vinegar soaks, to see if the limestone can be softened by the reaction with the acid in the vinegar. It may make prep easier, but it may also hurt your fossils,... so make sure to rinse thoroughly in water. Maybe some other folks will weigh in with their thoughts. Hope this helps some. Regards, Edited June 23, 2015 by Fossildude19 Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
PA Fossil Finder Posted June 23, 2015 Author Share Posted June 23, 2015 (edited) Hello, and welcome to the Forum. Actually, I have been a member on this forum for about two years. I don't post very often, mostly because my computer broke and I haven't been out collecting fossils recently. I have used white vinegar to help soften limestone, I will try that on some smaller pieces later. Edited June 23, 2015 by PA Fossil Finder Stephen Link to comment Share on other sites More sharing options...
Fossildude19 Posted June 23, 2015 Share Posted June 23, 2015 Actually, I have been a member on this forum for about two years. I don't post very often, mostly because my computer broke and I haven't been out collecting fossils recently. I have used white vinegar to help soften limestone, I will try that on some smaller pieces later. Oops! Must have been reading too many posts at the same time - Sorry 'bout that. Glad you are posting again. Good luck with the trilo prep. Regards, Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
PA Fossil Finder Posted June 25, 2015 Author Share Posted June 25, 2015 (edited) I've been looking into getting an air eraser, probably one of the cheaper ones to start. What psi is best for prepping fossils (my air compressor goes to about 40-50 psi), and what is the best abrasive to use? Edited June 25, 2015 by PA Fossil Finder Stephen Link to comment Share on other sites More sharing options...
Fossildude19 Posted June 25, 2015 Share Posted June 25, 2015 I've been looking into getting an air eraser, probably one of the cheaper ones to start. What psi is best for prepping fossils (my air compressor goes to about 40-50 psi), and what is the best abrasive to use? Harbor Freight Tools has a cheap one for about 28 bucks. Cheaper, if you have a coupon. They operate at between 35-60 PSI. I find that dolomite is good for harder matrix. For softer matrix, you can use sodium bicarbonate. (Baking Soda.) You can usually get dolomite from pottery supply places. I got mine from Axner Pottery Supply online. The prep section has some good threads regarding these things, for further information. Regards, Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
PA Fossil Finder Posted June 25, 2015 Author Share Posted June 25, 2015 Thanks for the help! The harbor freight eraser was actually what I was looking at anyway. Stephen Link to comment Share on other sites More sharing options...
TStodard Posted June 26, 2015 Share Posted June 26, 2015 Newb question: Is that "air eraser" like a mini sandblaster? Link to comment Share on other sites More sharing options...
Fossildude19 Posted June 26, 2015 Share Posted June 26, 2015 Yes, exactly what it is. Regards, Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
TStodard Posted June 26, 2015 Share Posted June 26, 2015 NIce. Stopping at harbor freight on the way home Link to comment Share on other sites More sharing options...
PA Fossil Finder Posted July 31, 2015 Author Share Posted July 31, 2015 Update: I did buy the Harbor Freight air eraser, and it works great with baking soda! Baking soda is less than a dollar a box at the local dollar store, so I got loaded up with tons of the stuff and started blasting some fossils. The limestone these Cryptolithus trilobites are in is hard enough in the unweathered areas that baking soda doesn't work. The weathered outsides of the limestone is quite easy to blast off though. These are the heads that I showed at the beginning of this post: Only some of the limestone would come off, so that is about as far as I can go with the air eraser. Here are a few other good ones: The upside down one is cool! Stephen Link to comment Share on other sites More sharing options...
Fossildude19 Posted July 31, 2015 Share Posted July 31, 2015 Great job on the prepping so far! Thanks for showing the update. Regards, Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
FossilDAWG Posted July 31, 2015 Share Posted July 31, 2015 Harbor Freight also sells an electric engraving tool that has a carbide tip. It comes to a point, not a chisel shape, but it does a reasonable job of chipping off rock. If you get one you should practice on some throw-away pieces before tackling anything you really want to keep. When you get close to the actual trilobite you should direct the tip at an angle to the shell, never directly at it. If you angle it right, and the matrix is not too "sticky", you can get the rock to flake off the shell. These things are not nearly as good as a real air chisel, but it's a lot better than scraping with a dental pick. I think I paid about $7. Don Link to comment Share on other sites More sharing options...
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