by Zoe McKellar
Peanut butter goes with a lot of things – it’s great with jam, chocolate, banana and bacon (honestly, don’t knock it until you try it), but it’s pretty good on its own, too. It can also be a highly nutritious addition to most diets when eaten in moderation, as it contains protein and healthy fats along with a range of essential vitamins and minerals. Overall, peanut butter is pretty awesome – providing you don’t have a nut allergy of course. In fact, it’s so amazing that not only can it be turned into a fantastic lunch, it can also be turned into diamonds…
Now, before you rush out to stock up on peanut butter let’s back it up a little. Unfortunately it’s not something you’ll be able to do in your kitchen and you won’t be making jewellery with peanut butter diamonds any time soon, but the science behind it is still really exciting.
Firstly, let’s think about what diamonds are – we’ll get back to the peanut butter. Although they can look pretty spectacular they’re chemically very simple and are completely made from a single element – carbon. Atoms of carbon can be arranged in different ways so there are several forms of carbon, sometimes called polymorphs. Diamond is one, another is graphite which you maybe familiar with. Graphite is used to make lots of things, including pencils, so it may come as a surprise to hear that it’s made from exactly the same thing as diamonds. The difference comes down to different combinations of temperature, pressure and time – diamonds need a lot of heat and pressure to form, hence why you won’t be making them in your kitchen.
So, we know that diamonds form under pretty extreme conditions, but where do these types of conditions exist? Scientists say that there are four main processes that are responsible for most natural diamonds. One of these processes is responsible for nearly all commercially mined diamonds. It happens hundreds of kilometres deep in the Earth, in the mantle, at a certain point where temperatures can reach up to 2200 degrees Celsius (4000 degrees Fahrenheit). It’s not only super-hot, pressure down there is over a million times higher than the air we breathe. The diamonds that form then reach the surface through deep-source volcanic eruptions which are incredibly rare and have never been witnessed in our lifetimes, which is what makes diamonds so special.
It’s really useful for scientists to investigate what happens in the mantle because it can help us to understand how the Earth formed. Space exploration has come a long way in the past few decades and we are learning new things about the universe all the time, but it’s hard to know what’s happening deep in the Earth because we just can’t get there. This means that scientists have to come up with ways to try to recreate what we think is happening down there.
Professor Dan Frost from the Bayerisches Geoinstitut in Germany has created an experiment that tries to mimic what’s happening deep below our feet to investigate the composition of the mantle. It involves crushing rocks under extremely high pressures. Professor Frost believed that in ancient times, rocks may have pulled carbon dioxide out of the oceans. When these rocks were pulled down into the mantle through a series of geological processes (like in subduction zones), the carbon was then converted into diamonds. This happened because iron-rich minerals in the mantle stripped away oxygen atoms from the carbon dioxide, leaving behind the carbon. Professor Frost created powerful presses to recreate these processes, and in doing so, he managed to make diamonds in some surprising ways.
But, where does the peanut butter come in? Well, peanut butter contains carbon, as do all foods (in fact, all living things contain carbon). Professor Frost experimented with various carbon sources, but after a request from a German TV station he decided to attempt to make diamonds out of peanut butter – and it worked. Mostly.
Peanut butter isn’t just made from carbon. It contains lots of different things, including hydrogen which is bonded to the carbon atoms. Hydrogen is very flammable and can be explosive when it combines with the right amounts of oxygen. When the hydrogen contained in the peanut butter was released it effectively caused a small (safely contained) explosion that destroyed the experiment, but only after they were able to form a diamond.
For the time being at least, we’ll probably need to stick to eating our peanut butter, rather than turning it into jewellery. Professor Frost may not be retiring with a fortune made from peanut butter diamonds any time soon, but his experiments may help to unlock some of the secrets that the deep Earth is hiding, even if that means a few more explosions. But then, what’s science without a little excitement?
Polymorphs: Two or more crystals or minerals that have the same chemical makeup but have a different appearance due to their atomic structure.
Mantle: This makes up the of Planet Earth’s interior and is mostly solid. It lies between the outer crust, which we live on, and the extremely dense core at the centre of the planet.
Subduction Zone: Where two Tectonic Plates come together and one slips under the other, dipping down into the hot mantle.
Tectonic Plate: A massive slab of solid rock that makes up part of the Earth’s crust.
Peanut butter nutritional info: https://www.bbcgoodfood.com/howto/guide/peanut-butter-healthy
Diamond formation: https://geology.com/articles/diamonds-from-coal/
What is carbon? https://www.bbc.com/bitesize/articles/zhhdqhv
Graphite vs diamond https://www.scientificamerican.com/article/how-can-graphite-and-diam/?redirect=1
Earth’s mantle https://www.nationalgeographic.org/encyclopedia/mantle/
Plate Tectonics https://www.livescience.com/37706-what-is-plate-tectonics.html
Subduction Zones https://www.livescience.com/43220-subduction-zone-definition.html
The man who makes diamonds http://www.bbc.com/future/story/20141106-the-man-who-makes-diamonds