The Dendermonde Mammoth: combating pyrite decay and the preservation of distinctive paleontological heritage

Accumulating fossil vertebrates is quite common amongst novice palaeontologists. Nevertheless, little curiosity is proven within the totally different phases one ought to undertake to deal with and safely guard these specimens for the long run. A great deal of fossils from historic collections are presently struggling due to years of storing and neglect. This may appear unusual, for the reason that fossils themselves have spent most of their time underground in very humid circumstances, however in actuality, issues solely begin proper after digging them up. Following-up on the restoration challenge of the “Dendermonde Mammoth”, we need to give an perception into the issues one can encounter when coping with the restoration and preservation of Pleistocene vertebrate stays which have remained untreated for the previous 20 years.

The invention

Within the historic Belgian metropolis centre of Dendermonde (French: Termonde), we discover the town’s historical past (together with pure historical past) museum known as the “Vleeshuis” museum (the home of meat retailers). It’s positioned in probably the most genuine sandstone buildings in the principle market sq. of “Dendermonde” (a province of East-Flanders). Contained in the majestic picket attic of the museum, the town’s oldest resident watches over the gathering, which is full of fossils and artefacts from the final ice age and prehistory. When strolling up the spectacular stone stairs that result in the attic, guests will encounter the paleontological delight of the “Dender” valley (the river flowing via Dendermonde). Once we take a better take a look at the knowledge indicators, we study that this mammoth was discovered between 1968 and 1969 by Mr Hugo Depotter, who additionally constructed the framework in 1975. The lacking bits have been accomplished with fossils from the Hofstade assortment from the Royal Belgian Institute of Pure Sciences in Brussels (RBINS) (Mourlon, 1909). In 1978, samples from the enamel of the molars had been carbon dated to find out absolutely the age of the mammoth cranium (Vanhoorne et al, 1978). Earlier than March 2017, the skeleton was in a quite untended state. Because of the lack of conservation over the past 20 years, the poor climatological circumstances underneath the roof and the absence of any curiosity by most people, the mammoth had misplaced its attraction.

Pyrite decay

Because of years of publicity and lack of any remedy, the bones of the Dendermonde Mammoth had been lined with a thick layer of mud and attacked by pyrite decay. The skeleton was exhibiting a number of visible outbursts of pyrite blooming out from the fossilised cartilage, particularly the left shoulder blade (scapula) and proper radial bone (Radius), which had been closely attacked by the standard grey-yellowish sulphur powder. This powder is the results of unstable pyrite bounding with oxygen atoms within the air. The response itself goes via totally different advanced phases and finally ends with the formation of FeSO_Four (iron sulphate) and SO₂ (sulphur dioxide). While you add water (moisture) to the equation (within the case of excessive relative storage humidity), additionally, you will be coping with the formation of H₂SO_Four (sulphuric acid). The simplified chemical response goes as follows:

4FeS₂ + 13O₂ + 2H₂O -> 4FeSO_Four+ 2H₂SO_Four+ 2SO₂

(Pyrite) + (Oxygen) + (Water) -> (Iron sulphate) + (Sulphuric acid) + (Sulphur dioxide)

It’s of the utmost significance that the affect of each water and oxygen, together with unstable pyrite, must be counteracted (Shinya and Bergwall, 2007). The response itself not solely results in the formation of corrosive merchandise such because the sulphuric acid, but in addition comes with a quantity enlargement. This enlargement is the principle cause why the bones will finally flip to powder and can destroy the inner constructions of the fossilised bones. Except for pyrite decay, the Dendermonde Mammoth additionally confirmed a considerable amount of desiccation cracks, because of the excessive variation in temperature. Such variations may even contribute to the fragility of the specimens, which is able to broaden the contact floor for oxygen and moisture, and hold the response mechanism going.

It could be simple accountable the storage circumstances, for the reason that mammoth is displayed instantly underneath the picket construction of the roof. Nevertheless, we also needs to keep in mind that the previous remedies of the fossil bones had been carried out quite superficially and most inner cavities didn’t profit from any earlier remedy. We additionally seen visible indicators of desiccation within the enamel of the molars. Specimens that undergo from pyrite decay, with out preliminary visible indicators of unstable pyrite blooming out of the inner constructions, will also be affected. This impact known as cross contamination and the Dendermonde Mammoth clearly suffered from it. Cross-contamination was clearly seen on each the bones and steel framework, the place the sulphuric acid even began to assault inert supplies.

The restoration challenge

The Belgian Paleontological Affiliation (Belgische Vereniging voor Paleontologie) took the initiative to arrange a restoration challenge with the cooperation of the Royal Belgian Institute of Pure Sciences (RBINS) and the Museum division of the town of Dendermonde (Stedelijk Musea Dendermonde). The aim was to revive your entire mammoth in only one week, with a various staff of specialists. All bones needed to be handled and restored earlier than mounting them on the steel body. To deal with all bones efficiently, the next steps had been wanted.

Step 1. Step one consists of eradicating all seen pyrite and mud in a managed surroundings. This may be executed through the use of needles, scrapers, scalpels and toothbrushes. An skilled preparator will sacrifice solely a small quantity of unique bone materials throughout this primary step.

The quantity of seen pyrite is a sign of the quantity of fossil bone that has already disappeared via pyrite decay. It is strongly recommended that the pyrite powder is eliminated whereas working underneath an exhaust set up. It will stop any corrosive airborne parts to wander across the room and be inhaled by the preparator. Private safety all through your entire course of is essential and really a lot so throughout this primary step. Eradicating pyrite decay releases fairly a pungent and unsightly sulphuric odor and, with none safety, will irritate the throat and lungs. It is strongly recommended that latex gloves and a surgical masks are worn when cleansing the bones with ethanol (to take away mud) and afterwards to take away the pyrite. Latex gloves will stop any response with sulphuric acid, which is able to irritate the pores and skin.

Step 2. Throughout the second step, the fossil bones are handled with a mono-ethanolamine thioglycolate resolution. This redox response will neutralise the unstable pyrite, which, in flip, will probably be washed away with pure alcohol (ethanol or methanol). Often a 2% to five% resolution of mono-ethanolamine thioglycolate with ethanol (EtOH) or isopropyl alcohol (IPA) is used. The primary stage is to immerse the bones within the resolution for about one hour. The pyrite contained in the bones will react with the answer, turning it darkish purple and even purple. We modify the answer each hour for the next three to 4 hours or till no change in color happens. Which means the pyrite has been stabilised. After this remedy, it is very important take away all traces of mono-ethanolamine thioglycolate, by rinsing the bone(s) with ethanol (EtOH) or isopropyl alcohol (IPA). Throughout this course of, it’s essential to regulate earlier restorations based mostly on reversible glues. Through the use of solvents, earlier restorations can loosen or break. It’s additionally essential to not harm or alter the unique patina of the bones by letting them dry too lengthy instantly after the mono-ethanolamine thioglycolate remedy.

There are some downsides to the usage of mono-ethanolamine thioglycolate. One of many major issues is that this methodology could be very time consuming and solely works properly with small bones. For the huge elements of the skeleton (just like the cranium, trunks or shoulder blades), we recommend the usage of the mono-ethanolamine thioglycolate remedy domestically through the use of syringes and tinfoil to forestall the answer from evaporating. Immersing all bones in giant containers could be too costly and impractical.

Step three. All unstable pyrite will by now have been handled, however this doesn’t imply that within the close to future there received’t be any outbursts of pyrite decay. The response mechanism remains to be working and the following step is to intrude with the response itself. One of the simplest ways to do that is to chop off the affect of oxygen and water, by treating all of the bones with a polyvinylacetate resolution. Subsequently, we use merchandise corresponding to: Mowilith, Osteofix and Paraloid b72, that are dissolved in acetone. By making use of this resolution to the bones, the polyvinylacetate resolution will penetrate deeply into the inner constructions of the bone, the place the acetone will evaporate and canopy the bone with a powerful movie. This movie will reduce off the contact with the air and, on the similar time, strengthen the inner constructions of the bone itself. It is very important execute this remedy in an aerated (ventilated) surroundings and, on the similar time, use latex gloves and oxygen masks to guard your self from the acetone fumes.

Step Four. After the inner and exterior remedy of every bone, we will focus on the remedy of the desiccation cracks. After the polyvinylacetate remedy, every bone could have a shiny look and can really feel much more stable than beforehand. Sadly, there’s not loads you are able to do about desiccation cracks. The most typical resolution is to refill the cracks with a (pH) impartial modelling clay (calcite paste), which won’t react with the remaining (stabilised) pyrite or the polyvinyl movie. After making use of the paste, it is very important decide about what color you need to apply to it. For the reason that Dendermonde mammoth is a part of a public exhibition, we selected to cover all restoration work by masking it with pigments resembling the unique patina of the bones. We used a totally totally different strategy when coping with a group that’s meant for scientific analysis, the place all restoration steps must be seen for everybody who want to do analysis on the specimens. The pigment is mounted on the bone with Paraloid b72.

Step 5. The final step is to reassemble the bones on the steel body, with out damaging them. Within the case of the Dendermonde Mammoth, we used steel wire to safe the place of every bone. After positioning, there’s the likelihood to repair the final scratches with calcite paste and pigment.

Conclusions

Pyrite decay is a extreme drawback in lots of paleontological collections and may unfold itself from one specimen to a different, inflicting numerous harm to a (scientific) assortment. Exterior elements, corresponding to variation in relative humidity and temperature, can play an essential function as accelerants throughout the chemical response. When requested how fast pyrite decay can have an effect on a group, there isn’t a normal reply. Inside a confined house, the place a group is saved, the sulphuric odor is likely to be the primary indication that the response is happening. The response itself takes place on a microscopic degree and, based mostly on analysis, appears to happen usually when coping with framboïdal pyrite (that is pyrite with a mineral construction trying like a raspberry). It’s crucial to observe and react in time by all doable means, when confronted with a visible signal of pyrite decay.

Lastly, remedy ought to by no means be seen as a everlasting treatment for pyrite decay, however must be repeated regularly, and positively when confronted with a visible outburst of pyrite decay on fossils. Solely then is there a assure assortment can final for a number of generations.

Profitable Collaboration

Because of this profitable collaboration, guests of the museum are as soon as once more in a position to meet the ‘oldest’ resident of the town of Dendermonde restored to its former glory. This challenge is the right illustration of how federal establishments, native authorities, and scientific organisations took motion and labored collectively for the preservation of nationwide scientific and paleontological heritage in occasions when the monetary means for scientific analysis are scarce. We will apply an essential lesson to our personal assortment based mostly on this restoration challenge. Within the first place, we should always acknowledge the significance of native paleontological historical past, and attempt to contribute to its preservation and scientific research by sustaining an open assortment for scientific analysis, and spend money on descent preservation of your assortment.

In regards to the writer

Anthonie Hellemond is president of the Belgian Paleontological Affiliation (BVP) and Vice-President Council for Earth Sciences (RAW-CST). He will be contacted at: bvp.voorzitter@gmail.com.

Additional studying

Germonpré, M. (1993). Taphonomy of Pleistocene mammal assemblages of the Flemish Valley, Belgium: Bulletin.

Koningklijk Belgisch. Instituut voor Natuurwetenschappen, 63, p 271-309.

Hellemond, A. (2017). De mammoet van Dendermonde, de restauratie van een verborgen paleontologische parel. Spirifer – Belgische Vereniging voor Paleontologie – Brussel 2017 (41) nr. 2 p. 2-Eight.

Lojen, S., Ogrinc, N., Dolenec, T. (1999). Decomposition of sedimentary natural matter and methane formation within the latest sediment of Lake Bled (Slovenia). Chemical Geology 159(1-Four):223-240 · July 1999.

Mourlon, M. (1909). Découverte d’un dépôt quaternaire campinien avec faune du mammouth et débris végétaux, dans les déblais profonds à Hofstade, à l’est de Sempst. Bulletin de l’Academie royal de Belgique, Courses des Sciences 2: 427-434.

Shinya, A., Bergwall, L. (2007). Pyrite Oxidation: Assessment and Prevention Practices. The Subject Museum, Chicago IL (Poster).

Vanhoorne, R., Van Strydonck, M., Dubois, A.D. (1978). Antwerp College Radiocarbon Dates III. Radiocarbon vol. 20 No: 2 p 192-199.

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