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.
Been a while since I updated the blog, but winter is a slower time on the fossil front. Compared to last winter, even purchases are down as I either have most of the stuff on offer, it's too expensive, or it's not in pristine condition. But I do have a trilobite coming in a few weeks, and one other I received not long ago. This post will be a potpourri of odds and ends. Lots of stuff coming up...
Pictured here is a wee Acastoides sp. from Morocco. It was cheap and very nicely articulated, so I added it to the trilobite family. I've also had a bit more cash in the PayPal account due to selling some surplus trilobites.
I also managed to spend an afternoon adding to my trilobite sketchbook with these two Russian beauties.
It's a rock! No, not just a rock, but a Russian rock, and a Russian rock containing an asaphid I am currently preparing. Due to the nature of the matrix, and my current tools, this is a 100-200 hour job. I'll create a separate post when it's done.
Hobbling my preparation efforts has been a clogged air hose, likely in the built-in moisture trap for my Paasche AECR. One might think a basic air hose with a 1/4" - 1/16" would be a cinch to replace, but three hours of hardware store visits and plenty of time searching the web says otherwise. I finally got my part and am ready to get to the next critical phase in the prep, which involves swapping between scribing and abrading due to the stickiness of the matrix.
And that wasn't the whole of my prep equipment frustrations, either. I had just been talking with my friend Kevin, saying that I've gone over a year without needing a filter on my lines. Well, no sooner than I said that, the scribe starts acting more like a garden hose. So a trip to Princess Auto to fix that, and to locate a replacement hose (see above). I was also having serious air leak issues, and teflon tape for my big clumsy fingers usually results in my exhausting all the blue words I know, so I've gone for thread sealant instead. The filter/desiccant has already made for a much drier scribing experience. Nothing can be more frustrating than doing precision work under the scope while maintaining critical control of the tool than when it sprays water all over the fossil, turning scribing dust into cakey, opaque mud. And also pictured is a resupply of those handy nitrile gloves.
So when is the first dig of 2019? I'm hoping this weekend, weather and opportunity pending. I've got some other trips planned, too. It will be fantastic to get this season rolling and spend time with my favourite field comrades again as we swing hammers as spring clamours!