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Excavating trilobites!

Finding these invertebrates is not easy work, the local fossil diggers often armed with only hand tools, crowbars, picks, cold chisels and heavy lump hammers, work away at rock faces...

Finding these invertebrates is not easy work, the local fossil diggers often armed with only hand tools, crowbars, picks, cold chisels and heavy lump hammers, work away at rock faces sometimes in deep trenches hewn out of the mountains and in the desert.

Large wall feature trilobites

The local knowledge which excavators hold and Berber villages they invariably inhabit in the searches of the sparse desert regions, help these fossil hunters hone their techniques and skill for the recognition of trilobites and the patience needed to work in the harsh environments and basic conditions. Often diggers will leave their village homes for several days bivouacking in hot desert oasis and nights in cold mountain huts in the search of the invertebrates.

small spiny trilobite

The locations of productive trilobite sites are kept secret as much as possible, however in this land that is not too long! local grapevines trickle the news of new finds and the teams of local diggers layout unmarked claims and set to work. some of these sites are 200-100km into the desert. The terrain such that machinery cannot easily be taken to the source. The fossil hunters have meagre means to supply expensive compressors to drive tools, so all is achieved with man-power only. Work in the heat is lengthy and arduous and the author has often admired the tenacity of these local men eking out an income in uncomfortable positions often for comparatively little gain when considers the weeks and months required to clear tonnes of rock for one 500 gram pebble containing a fossil trilobite.

How does one find the fossil trilobites in the fossil-bearing rock? At the fossil site, the fossil bedding seam is broken up into smaller constituent parts, these rocks can be now dinner plate-sized to hand-sized boulders or large pebbles, with a well-practised blow these are cracked in half. This splits not only the rock but also the arthropod in two. If in fact, it is a whole arthropod specimen. All too often it is not, just the glabella, thoracic segment or pygidium (head, body part or tail sections). If it’s a lucky discovery of a full carapace (exoskeleton), of a trilobite the whole boulder is very carefully glued back together.

Large spiny trilobite

The arthropods body parts are darker than the limestone matrix which entombed it can be easily identified. The chitin carapace which has calcified during the fossil process (per mineralisation), absorbing minerals from the once surrounding seabed silts, can be distinguished and therefore can be located in the pieces of rock.

Back in the workshop or laboratory with specialist pneumatic tools and air abrasive techniques with tools driven by compressed air, work begins on the outer surface of the rock very carefully and slowly. Sometimes over days and weeks, broken down mechanically bit by bit. The limestone boulder is by attrition reduced to the desired form. The final process is often to carefully polish the arthropods carapace using fine silicates using a miniature air abrasive or blasting tool. This naturally enhances the colour giving (in the case of black Devonian trilobites), a very bright black sheen over the surface of the carapace and all its pustules, bumps and lumps, along with the segments and lobes of the thoracic body making the arthropod 'jump out' as if still alive in a three dimensional way which is technically referred too as ‘fully inflated’.

We hope you enjoyed this brief account of trilobite hunting, we shall post more so keep revisiting our blogs to read more reports and news.


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