typical Moroccan "butchery"
|The importance of specimen preparation |
In decades past, extraction of trilobites and other fossils was largely a matter of hoping that separating layers of sediment with a geologist's hammer would reveal specimens close to whole. If the fossil matrix was uncooperative, and specimens were only partially revealed, then tools such as brushes, steel dental picks, and power sanding heads might be used to attempt to remove the matrix. In Morocco, native extractors still use hammer and nails, leaving heavily damaged specimens that are very sad to see indeed! Compare, for example, the two specimens of the phacopid trilobite Hollardops sp. (previously called Metacanthina) from Morocco. The one on the left was extracted crudely, while the one on the right was prepared using modern equipment and methods.
|STAGE 1: Roughing out|
| ||Using an air scribe (such as Chicago Pneumatic), the surrounding matrix is carefully removed from around the trilobite, but care is taken not to touch the trilobite itself. After an hour of this, the very top of the trilobite specimen is revealed, and the experienced preparator can identify it, anticipate its shape within the matrix, and remove matrix accordingly with confidence. |
| ||To roughly expose the trilobite, the correct grit is selected, and the matrix is air-abraded away from the trilobite, alternating with air-scribe to remove thicker portions of surrounding matrix, and sculpt the matrix around the trilobite. The preparator's experience with previous trilobite specimens of this taxon is very important here, since the goal is to expose the trilobite down to the edges of the dorsal shell, yet provide a strong enough foundation that those edges aren't over-exposed and prone to breakage. |
| ||The edges of the dorsal exoskeleton are completely exposed, alternating between air abrasives and air scribe, until the rough stage is essentially complete. While the fine air-scribe can be used to remove the larger portions of matrix still clinging to the dorsal shell, this becomes risky when attempting to remove matrix between the segments or caught in sutures and deep furrows. At this point, the air-scribe is set aside, and only air-abrasives are used in stages 2 and 3. |
|STAGE 2: Finishing|
| ||Using only air-abrasion under a stereo microscope, the matrix between segments and in furrows and sutures is carefully removed. It takes about an hour for an inch-long specimen in relatively hard matrix (such as the typical Moroccan material). Great care must be taken not to undercut the matrix at the edges of thoracic pleurae while removing matrix from between the pleurae. As the work nears completion, finer, and softer grits are used under higher magnification. |
|STAGE 3: Final touches|
| ||At the end of the process, all matrix overlying the trilobite is gone, and only a pristine trilobite exoskeleton is exposed, sitting firmly upon an undamaged and nicely sculpted piece of original matrix. |
|The finished specimen|
| ||After about 4 hours of preparation the finished specimen was ready to photograph and send out to prospective buyers. It sits proudly today in my modest assortment of representative trilobite orders and suborders. It is a complete joy to look at: the fine structures of the glabella are revealed, the cornea over each brown holochroal eye is smooth and intact, and the specimen is ready for serious study. Kevin prepares specimens as one means to support his graduate work in paleontology, so I'd encourage you to contract him to prepare your bugs. You can see the excellent results! |