eli5: Do you have to carve Fossils out of the stone or will they pop out in the form they are in, when the stone it split open?
In: 8
Hiii 🙂
As it was already mentioned- it indeed depends on the fossil as well as on the matrix (the rock, sediment) that contains it.
There are many different techniques of fossil preparation, I can briefly describe some for you 🙂
The majority of fossils are found in sediments. In unconsolidated sediment (sand, clay, ash) you can find “free” fossils and some of them you can even safely take out- I work for National Museum in Prague and I usually pick out microfossils from caves’ sediments. Even though I just take a tweezer, pretend to be a Cinderella and carefully pick fossils out (tiny rodent teeth, vertebrae, leg bones etc.) the sediment is usually rinsed and dried in advance in order to get rid of the mud and clay particles. However, you can say that they just “pop out in the form they are” from these kinds of sediments 🙂
Sometimes though, big bones can be found in unconsolidated/ semiconsolidated sediment. These are usually too fragile to “just take out” so paleontologists usually create a plaster or burlap to wrap the fossil with the surrounding sediment in. This technique also protects the fossil during transportation. The plaster is then taken to the fossil preparation lab where it’s opened and worked on- either with paint brush, dental pick or even airbrush.
There are also many ways and techniques to consolidate the fossil prior to the preparation if it’s too fragile or fragmentary. For that, different types of glues and consolidators are used.
Most of the sediment is however, compressed into rock over time. Then there are two preparation options available. Mechanical and chemical.
Mechanical preparation is the most common method. Various tools (dental tools or air- powered micro jackhammers) are used to chip away the surrounding matrix while carefully exposing the fossil. Again, the fossil can be strengthened in advance, which helps it to be more resistant to the vibrations of preparation tools.
Chemical preparation is used when the fossil and matrix are composed of different chemicals (for example silica fossils in limestone). In such case, surrounding matrix can be easily dissolved without any damage to the fossil.
Anyway, if you just want to look for fossils yourself, I am sure you can find a place in your area where they just pop out as they are 🙂
I wanted to end this small overview by uploading some photos of the fossils I prepared, but apparently it is not possible here on Reddit ( I am new here) 😀
Hope I did your question justice, have a great day! 🙂
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