Trilobite Preparation: From Quarry To Display
It looked like a rock. It felt like a rock. On closer inspection, it even exuded the distinctly earthy aroma that made it smell like a rock. The piece in question was expectedly heavy and rather nondescript, a predominantly dark grey mass featuring a blend of smooth and jagged edges that provided this particular five-by-five inch sedimentary stone with the appearance of a somewhat squashed softball. To the vast majority of people strolling through the Denver Fossil & Mineral Show that day, the specimen was nothing more than what it appeared to be. It was, indeed, a rock! Yet for whatever reason, this particular rock had drawn the interest of two intrepid souls who had begun studying it with a thinly veiled passion. At first they examined it with their naked eyes, holding it mere inches from their faces while rapidly commenting back-and-forth throughout the procedure. Then one of the two decided to pull out a pair of well-worn glasses from his jacket pocket, somewhat haphazardly placing them on the bridge of his nose while never missing a beat in the running discourse.
The rock was carefully rotated and studied from seemingly every available angle. Not a millimeter of its craggy surface missed detailed inspection. Finally, a minute later, a hand lens was borrowed from a near-by acquaintance and the examination moved on to an even more intense level of observation. The two proceeded to turn the rock over and over, angling it this way and that, making sure that the best possible light could shine upon certain key nooks and crannies. One even used a bit of saliva to wet-down a spot of particular interest in order to make it appear more prominent upon the stone surface.
It was then that the finger pointing began, with that one small area of the rock drawing their most ardent attention. Those strolling by the two began to be pulled into the scene by both the excited conversations taking place and the ever-wilder gesticulations that seemed to increase in direct accord with the pair's focus. What were those guys looking at? Was it a speck of gold, or possibly some sort of gem? Maybe it was a Martian meteorite? Actually, it was nothing of the sort. But to the eyes of our two paleontologically-inclined rock hounds, what they had stumbled upon was perhaps even more exciting than a chunk of a distant planet or even a diamond-in-the-rough. With their highly trained eyes, these fossil preparators had noted a series of nondescript dark marks permeating the rock surface, none bigger than the width of lead in a #2 pencil.
What they had found housed within this particular Devonian-age rock was the barely-there cross-section of a rare species of Moroccan trilobite, the exposed segments caused when the specimen had been revealed -- probably by a well-placed hammer blow -- along a rock's vertical plane. And as both were well aware, the best trilobites in the world were usually prepared from specimens discovered in cross-section, where there was far less chance that delicate genal spines or eye facets could suffer damage during initial extraction. Once they had negotiated a purchase price with the ever-eager North African fossil dealer who was offering the piece for sale, neither could wait to get this particular rock back to their lab and start what would be at least a 15-hour preparation process which would hopefully reveal in all of its former glory the trilobite treasure hidden within the 450 million year old matrix.
“Some people see a beautiful trilobite in a museum display or in a private collection and they assume that it was originally found that way,” said Zarko Ljuboja, an Ohio-based fossil preparator whose specialty is trilobites. “Occasionally, especially with some Lower Cambrian trilobites, that can happen. The shale is split and the entire trilobite is revealed. But most of the time the trilobite is either buried in the rock with only a small piece of shell showing, or you see them only in cross-section, where, if you're lucky you'll see the thin outline of the trilobite's profile. It usually takes a bit of imagination, and a lot of skill, to see that trilobite and then transform it into something special.”
It is believed that Michelangelo once explained his approach to sculpture by stating that he merely freed already-existing pieces of art from their surrounding stone. Certainly such an observation provides key insight into the breadth and scope of his genius. But while the Renaissance master's words may have reflected the unique thought process through which he created his renowned works, in the case of trilobite preparators such an approach is exactly how it's done. Perhaps those who work with fossils don't possess the inherent artistic elan of the famed Michelangelo, but when all is said and done, it is they who are the ones who truly free existing forms from their encasing stone matrix.
Yet for all their apparent skill, the work done by trilobite preparators has only become recognized during relatively recent times. Particularly over the last two decades things have changed radically within the trilo-prep world. If we venture back to the late '80s, fossil preparation was still basically an arduous, often haphazard process where acid baths, wire brushes and hand-held dental tools frequently left the resulting trilobite as little more than a bruised-'n-battered remnant. By the dawning of the 21st Century, however, prep work had evolved into a state-of-the-art procedure employing an exotic array of custom made electric drills and air abrasive machines. In the proper hands, each of these devices was capable of transforming half a billion year old trilobites into nearly flawless specimens guaranteed to garner admiration from both the scientific and collecting communities.
Many of these “next generation” trilobites now feature delicate free-standing spines -- some no thicker than an eyelash -- and amazingly detailed compound eyes, which make them both a joy to observe and a pleasure to study. Thanks to these recent advances in preparation techniques, trilobites have garnered a new, and perhaps unexpected prestige. Not only do they now posses increased value as scientific specimens, with more detail than ever being exposed to studious observation, but they have also emerged as beautiful pieces of natural art that have attracted a surprisingly large mainstream audience.
Getting a trilobite ready to attain such a lofty plateau, however, is far from easy. As one might imagine, each unprepared specimen presents its own particular set of problems and predilections. Some trilobites may come from Canadian quarries where the rock is so hard that proper preparation is nearly impossible. Others may hail from thinly-bedded sedimentary outcrops in Ohio where the demarcation between trilobite shell and matrix is, at best, marginal. And others may be found in Russian shale so easily shattered that it transforms the initial stages of the preparation process into little more than assembling a giant jigsaw puzzle. Such challenges, however, apparently come with the Paleozoic territory, and the modern breed of trilobite preparator seems to have a handy solution for just about every problem that may be thrown his way.
“Preparing trilobites is always a challenge,” said Ben Cooper, recognized as one of the world's leading trilobite preparators. “These days people expect free-standing spines on certain Moroccan and Russian specimens, and they always expect every trilobite to be perfect. Even the jobs that would appear relatively easy can suddenly turn difficult when you encounter something unexpected, which could range from a crinoid stem laying directly on top of the trilobite, to a pygidium that has become detached from the rest of the specimen. You have to keep a bag of 'tricks' handy -- everything from glues to resins to epoxies to solidify matrix, fill in missing shell and fix what you might accidentally break.”
Those who spend their professional lives preparing trilobites for study or display are an admittedly unusual lot, with the majority of these men (and, yes, they are all men) seemingly determined to both walk and work to the beat of their own drummer. Many might best be described as introverted eccentrics, artistically inclined independent thinkers, and even more significantly, independent doers. They're the kind of guys who would rather bypass their $30 an hour prepping fee for days-on-end in order to fix their own roof… when they could just as easily hire a roofer for $20 an hour. But major financial gain never seems to be a primary motivation for this lot. Otherwise, they'd argue, why the heck would they prepare trilobites in the first place?
Most seem to be nocturnal by nature, preferring to ply their prepping craft long after those who follow a more traditional 9-to-5 work schedule have turned their backs on another day. It is in the relative quiet of the wee hours that these “magicians” do their best to transform even the most initially obscure, geologically obtuse trilobite specimen into a true Paleozoic prize. Sitting for prolonged periods with their eyes glued to their high-powered binocular microscopes with their skilled hands often buried within the confines of well-ventilated prep cabinets (the fine-grained silicate powder used to remove surrounding rock from trilobites can cause major lung problems if inhaled over long periods of time), these guys seem happiest with only the ever-present whine of their air abrasive machine to keep them company.
Despite their skill and dedication, however, dealing with these unusual men can at times be more than a bit frustrating for those who collect and study trilobites. Prep guys rarely answer the phone (even when they're awake during daylight hours), usually don't respond to e-mails, and motivating them to finish a particular specimen can often turn into a true battle of wills… and patience. It has been often jocularly said of one particularly talented Midwestern prep master that if you send him a trilobite on Monday, he'll get it back to you by Friday -- just that the Friday in question may be two or three years hence.
Another prepper, this one based in New York State, has become renowned for seemingly renaming every specimen he works on… even if the scientific nomenclature for that particular trilo-type has been widely accepted for decades. Yet another has become infamous for literally putting out the “gone fishing” sign every time there is a salmon run near his Northwestern home, even if he is in the midst of an on-deadline project for a major museum.
Still, despite their occasionally curious and almost always unpredictable nature, the undeniable fact is that without the creative work put forth by the 20 or so individuals world-wide who've dedicated their careers to the art of fossil preparation, life simply wouldn't be the same for any of us who revel in those ancient arthropods called trilobites. By taking raw fossil-bearing stone and then transforming its contents into objects of natural beauty and scientific importance, these prep masters have found a unique way of almost bringing 500 million year-old creatures back to life.
“Those who prepare trilobites generally love what they do,” Cooper said. “It can be frustrating at times, especially when things don't go as planned and what you were hoping would turn out to be a complete, articulated specimen turns out to be nothing more than a partial. Yet it can also be a very creative process, one that also has the aura of scientific importance. You never know when you might reveal something that is new to science… perhaps a species that hasn't been seen for 500 million years. Sometimes you find yourself cranking out a ton of common specimens, and you know you're doing it just to pay the bills. But sometimes you get the chance to work on something special. And when you're sitting there late at night, staring into a pair of trilobite eyes that you've just uncovered, there's no question that there's nothing else in the world that I'd rather be doing.”
A typical "state of the art" trilobite preparation lab.
Traditional hand preparation using fine precision instruments (e.g. scribes, scalpels, rotary tools) under a stereomicroscope is augmented with micro air-abrasion (under an air evacuation hood) using a wide variety of abrasive grits. This micro sandblasting permits the removal of matrix surrounding the trilobite without damaging the shell exoskeleton and fine details such as spines and eye facets.
Master preparator Ben Cooper, using an air scribe to define features on an Olenoides superbus.
The completed Olenoides superbus demonstrating free standing spines.
The following pictures illustrate the progression from a “fresh from the quarry” fossil, encased in matrix, to a spectacular museum worthy specimen.
Fresh from the quarry, the pygidium of a rare Acanthopyge from Morocco can barely be seen. The pieces of matrix containing what is hoped to be a complete specimen have been assembled.
Preparation with an air scribe is begun on the hard Devonian limestone revealing part of the pygidium and thorax.
Other pieces of matrix are added to expose more of the trilobite.
An essentially complete trilobite is revealed, though tips of pygidial and genal spines remain covered.
More detailed prep work shows sweeping spines on the pygidium.
Genal spines are uncovered on the cephalon.
The complete specimen -- ready for museum display