Fossil Fever: Permineralization vs Carbonization

Images by James St. John

Many roads lead to fossilization, but they all require the stars to align as the perfect conditions allow animal and plant remnants to remain preserved in the ground for millions of years!

A two very interesting methods of preservation are Permineralization and Carbonization. Let’s learn a little more about each one!


Permineralization is the process of penetration and replacement of an animal or plant’s internal structure with mineral deposits.

In order for this to happen, the following process must occur.

First the organism must be buried shortly after dying, so that its remnants are not lost to the elements and other predators. Next, mineral-rich groundwater must seep into the area of the burial. After this, minerals from the groundwater can begin to fill the pores of the organism’s tissues, and begin to replace the original structure as the decomposition process begins. As each cell begins to die off, it is filled in with mineral deposits.

Depending on the type of minerals being deposited, this process can result in a very accurate stone structure of the original animal or plant. The most common minerals in this process are silicates, carbonates, and iron.

In some fossils that have gone through the permineralization process, only very distinct cell types can be differentiated, while the right conditions can allow for details so fine that organelles within individual cells can be seen!

When minerals have completely replaced all the original structures of a permineralized fossil, that fossil can be said to have been petrified (petros = “turned to stone”).

If you’re a big fan of fossils and specifically the permineralization process, you may want to take a field trip to the Petrified Forest National Park in Arizona, which contains and abundance of petrified trees from about 225-207 million years ago during the late Triassic Epoch of the Mesozoic era. Also uncovered at the park is a huge collection of vertebrate fossils from the same period, including early theropod dinosaurs, crocodile-line archosaurs, temnospondyl amphibians, and more.


Carbonized fossils are also known as compression fossils or carbon film fossils. They result when an organism is crushed under extreme pressure over time. During this process elements including hydrogen, oxygen, and nitrogen are siphoned off, and just a film of carbon residue remains.

Typically carbonized fossils are of plants, though fossils of insects, fish, and crustaceans have been found as well. Though they only give a 2D impression, these fossils can also preserve a large amount of detail, such as the leaves and veins of a plant, and sometimes even individual cells!

Carbon film fossils are also often easy to categorize via the process of carbon dating. Carbon-14 has a half life of 5,700 years, and scientists use this knowledge to test the carbon and get an accurate reading on when the organism’s decay process began.

Carbon fossils also are still a major fuel source for humans today, although more sustainable energy sources are becoming increasingly popular every year. During the later part of the Carboniferous Period huge forests and giant swamps flourished. As masses of dying plants were buried in these swamps, they underwent the process of carbonization. These turned into the large reserves of coal that are mined for their energy today.

So which will it be? Petrified stone statues that allow us 3 dimensional view into the world of plants and animals past? Or 2D prints of accurately dated flora and fauna past, many of which have fueled modern human existence for the last 150+ years! Choose your team soon because the competition starts at 11:00 AM ET on 5/23 and goes for 48 hours! Bonus information is detailed in your notifications.

Swag: The top scoring player on the winning team wins a t-shirt, plus a sticker/magnet set! Second and third place on the winning team will each also win a sticker/magnet set.