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When I got down to Georgia my wife had an early birthday gift for me. She always tries to get me things that are fossil, rock climbing or backpacking related. This time she said that she searched the Fossil Forum site and some member was talking about chisels, so she bought the ones below. These should be great when collecting my Ordovician or Pennsylvanian road cuts.
@snolly50 was nice enough to send me a mess of a Moroccan concretion to play with recently. It started out as what appeared to be bits of vertebrae poking out of the block. After about 4 hours of scribing with my ME9100, I had uncovered a few scraps of bone but no centra were evident. The natural crack that you see opened up from the vibrations of the scribe and no robust bone was evident in the crack either. With John's permission, I began exploring the back of the block, hoping to find something worthy to prepare. Bingo, I found some bone. The crack happened to peel through a small section of the centra rather than through a full cross section giving the appearance of a lack of large bone in the concretion. 4 or 5 hours later and the verts were mostly exposed. Unfortunately, this concredtion had a thin layer of softer rock on the outside and a significantly harder inner core. The matrix is MUCH harder than the bone and I fought the bones trying to crumble the entire time. This has copious amounts of Vinac on the bones to stabilize them. At this point, the ME9100 is almost making no progress on matrix removal. Enter the Super Jack scribe. This beast will plow through the matrix. It ultimately saved me around 12 hours of scribe work on this project. The one thing you have to be careful of is the increased vibrations to the block with the more powerful scribe. I spent more time consolidating and aggressively applied Vinac to any bone as it was exposed. Prep progressed quickly with me alternating between the Super Jack for bulk matrix removal and the ME9100 for close to the bone work. Including the exploratory time, I have 16 hours into this prep at the finish. I left some of the tool marks on the matrix rather than completely smoothing it out because I think it highlights the rugged nature of the piece and most Moroccan stuff has tool marks. The ones I have seen that are totally clean look off to my eye. It would be like @RJB leaving tool marks on his crab concretions. None of them have it so if they were there, it would look wrong. Here's the final product.
As part of my fossil preparation process I have the need to reduce the size of the background rock on some specimens collected in the field. My preferred tool is a 300mm slab saw I acquired a while back made for lapidary work as this has very little vibration. Normally if I use it to cut agate or similar rock I use the cheap home brand baby oil, works a treat, good for the hands and no smell after. On the test piece I did with the softer stone the oil permeated into the rock base and the fossil and cleaning in detergent straight after only got the surface clean. I doubt the baby oil will harm the fossils but suspect it will prevent permanent gluing of damaged material and leaves and oil stain that I do not want. I tried a second piece and painted the surface with paraloid to seal, but the cut edges still stain. So currently I drain the coolant from the saws sump and replace with water cut the fossils and then drain the water from the sump as the water will cause the diamond blade to rust. The question - does anyone know of a coolant that can be used that will not seep into the softer fossils / rock and will not rust the diamond blade? Mike D'Arcy