FFF = Flat Fossil Fish!

When I was in Tucson, AZ for the annual huge fossil, gem and mineral show in January I picked up five small “plates” of limestone each having a fossil fish encased in the stone. I bought these unprepared so I’d be able to practice new methods of fossil preparation. These thin (varying from 1/4” to 1/2” thick) plates of limestone are quarried from a famous area called the Green River Formation near Kemmerer, Wyoming. The fossils found in this ancient lake bed deposit are dated to be @50 million years old.

The specimens I picked up are from a part of the sea bed referred to as the “sandwich layer.” It’s a layer between where more rare and special finds are often located. Hence, they weren’t expensive to acquire and I could feel okay with myself for practicing on them. I’ve seen wonderful specimens from this Green River Formation for a long time in books and museums and at fossil shows like Tucson, talked to dealers who prepare them to ask about techniques to do so but had never touched one myself before. The five plates I picked up were from this sandwich layer which only seems to show a couple of the most common fish found in the formation: Knightia alta and Diplomystus dentatus. Therefore they were inexpensive and sold for just this purpose – for dummies like me to practice on! These small fish are kind of, distantly, related to modern herring.

I’ve prepared four of the five fish so far and been learning as I go. I’m getting a little better at my technique and figuring out the best ways to go about it. The first one isn’t as well prepared as the fourth one I just finished but I’m learning and that’s what it’s about. I’ve learned my air scribe tools (compressed air mini “jack hammer” type tools) are too much, the micro blaster (a type of sand blaster to remove rock from fossils) is generally too aggressive as well and that picking off one small spot of stone at a time from the surface with sharp pin vises, needles and other pointy tools is the way to go. Very slow and gives the best results. The work is pain staking as we do our best to pick away thin layers & grains of stone to expose the flattened impression of the fish scales, fins, vertebral column, eye socket, mouth parts, tail and general outline of the body of the fish. They were buried under layers of fine sediment which hardened and became limestone leaving just this thin impression in the rock. It’s like trying to pick away stone from a fragile piece of paper and not disturb the paper; not a chore for the impatient!

I didn’t do any video recording on these first four but will try to do a time-lapse video of the preparation, or at least some of the prep, on the last one I work on. Time lapse would show the process and show the fish being exposed little by little as we go. I’ll post that in a future entry here.

In the meantime, here’s a set of still photos from the most recent little fish we cleaned up. In order from the beginning of exploring to find out where is what, to the final product. Enjoy

Here’s a sample of the tools we use to hand pick the rock away from the surface of the stone. This is almost a “before” photo but note where I started to clear away some where the bumps of vertebrae were showing through.
After the first session of preparation just a little is exposed. I hold the plate up to the light, sunlight is best, to pick up the faint bumps on the surface that show where something is hidden below.
After another clean up session; more is exposed and the natural dark fossil is showing up.
More! Head is to the left and tail to the right. Look closely at the head and you can start to make out the mouth parts showing through where stone has been gently picked away.
Now we’re getting somewhere. The void to the left is the eye socket and you can pick out the open mouth posture. Still more to go…
And here’s the final result fully exposed and outlined using an air scribe to make deeper indentations surrounding the fish.