As I posted last time, I received a block containing the trilobite Asaphus lepidurus for me to prepare. Despite the three of this species I've prepared before, this one was by far the toughest due to the nature of the matrix being hard, sticky, and calcitic. It meant very slow scribing, micrometre by micrometre, under high magnification. Of course, I was having plenty of problems with my equipment that added to the aggravation.
This is the block when I got it, and then after an hour and a half of patient scribing with an ARO clone with the not so great factory tip. As thick as the block was (with trilobite at the bottom), I couldn't risk a chisel... So it was the long way down.
Several more hours as I also work the matrix down. The plan is to have the trilobite standing in this orientation, sitting in a depression. The matrix is starting to play tricks with my eyes. At this point, I'm slowly revealing the right pleurae, heading for the axis, and working around the cephalon.
This stuff is sticky, and largely impervious to abrasion even at higher pressures. It took several hours to find the other eye, negotiating very carefully so as not to accidentally scribe it off. Once the pleurae and axis were largely revealed, working that top of the cephalon took eight or so hours on account of extra stickiness. I also didn't want to knock off the diminutive tubercle by mistake.
After the left side pleurae are exposed at their tips, let the long abrasion session begin. I swapped between the Paasche with the 18 gauge dispensing needle (the disposable needles just arrived yesterday just in time) and the pin vise. There were several very stubborn, translucent bits of calcite to slow me down.
I finished it off with some matrix smoothing, and this is the end result. Measuring 80 mm. Despite the limits of my current equipment, and the unholy horror of this matrix, I managed to do some justice to this trilobite, exposed for the first time in 450 million years.