How do paleontologists remove fossils from rocks? With acid, power tools and a lot of patience
Ancient bones and teeth glow under the bright lights of the Melbourne Museum, surrounded by a crowd of excited children – and more than one captivated adult.
But under this commotion, in the basement of the building, are these fossils taken out of their rocky tombs and cleaned up for display and for scientific research.
Pieces of limestone in different stages of processing are found around the part. They come in all sizes – from tiny, delicate bones lodged in matchbox-sized pebbles to heavy slabs that require a hydraulic lift to move them.
And forget what you saw in Jurassic Park, where paleontologists gently sweep the sand and stones from perfectly preserved skeletons. In reality, it is a much noisier process.
Fossils last for millions of years because oftentimes they are surrounded by hard rocks.
So paleontologists often use special power tools, acid – and a lot of patience.
Most of the bones and teeth in the museum’s basement are fossilized remains of ancient whales and dolphins that swam in the oceans 15 million years ago.
When they died, the bodies of the animals sank to the bottom of the sea and were covered with silt and mud. Over time, this viscous sediment solidified into limestone.
Nowadays, this limestone forms towering wheat-colored cliffs that mark Victoria’s surf coast. As the wind and waves move away from the cliffs, they expose bones and teeth embedded within, which are sometimes spotted by eagle-eyed surfers and fossil hunters.
Paleontologist Ben Francischelli is one of those fossil hunters. He is part of a group that regularly scans the coast at low tide for ancient remains, which stand out in black against the limestone.
And while finding a fossil takes skill, it’s the easiest part of what’s to come.
Before trying to remove a fossil they found, they pour it and dip it in a liquid called a paraloid which hardens like glue, giving strength to the ancient remains.
Then, if they can, the crew use scissors and crowbars to safely remove the fossil and surrounding lump of limestone, which they then load into a waiting car. It can be a tough yakka … but the hard work goes to the museum.
Limestone and encrusted fossil is taken to the basement of the Melbourne Museum. Here the process begins to remove the fossil from its rocky nest where it has rested for millions of years.
First, paleontologists need to remove as much of the surrounding limestone as possible without damaging the precious fossil inside. Often that means sticking it in acid for a few days.
To do this, the fossil is transported to the museum’s acid treatment room, where plastic tubs and sinks line the walls.
Although it is quite hard, limestone – which is made of a material called calcium carbonate – dissolves in acid.
Shatter a piece of limestone in acetic acid, also known as vinegar, and carbon dioxide bubbles start to form on the surface of the rock.
The paraloid, which fossil hunters added earlier, helps protect the fossil from acid. Paleontologists will often also cover the exposed fossil with lacquer.
After a few days, depending on the volume of limestone, the fossil is rinsed with fresh water to remove the calcium salts that accumulate during the chemical reaction between acetic acid and calcium carbonate.
Then it’s time to clean up the fossil for the first time, says Dr. Francischelli.
“[The acid bath] usually turns some of the sediment into slush, which we can then just gently wipe away with a brush, ”he says.
And then he brings out the power tools.
The big guns
The main fossil preparation workshop is located right next to the acid treatment room.
It has high ceilings and industrial fans, much like a standard workshop, but instead of a range of screwdrivers and drill bits, these tools range from delicate brushes to modified dentist drills.
Before getting stuck in the fossil, Dr Francischelli says, “you look at the way the bone goes around through it, because that very first bath usually removes a lot of the surrounding sediment.”
“And then you have to ask yourself the question: should I reduce this specimen further?
Big guns aren’t as big as your standard household drill, but these paleo tools pack a punch.
Before we begin, Dr Francischelli dons hearing protection, goggles, and a mask, as this part is incredibly loud and dusty.
The air chisel flakes off at rock level while the fine point drill is best used for more delicate jobs. Still, the sound is not pleasant, to say the least.
And things don’t always go as planned.
Sometimes the bone can break – perhaps because it was accidentally hit by a tool or simply vibrated too much.
When this happens, then begins the slow work of picking up all the fragments and carefully gluing them back together.
Once the fossil has been cleaned up, says Dr Francischelli, he and his colleagues can correctly identify exactly what they have.
“And if we know we have something special that’s why we take the time to prepare it in the first place, we can try to figure out what kind of species it is,” [or] if it’s a new species, ”he says.
“And if that’s the case, or if it’s something really important, we can name it in an article, we can describe it in the scientific literature, and use it to educate the masses about paleontology as a whole. . “