Why are shark teeth different colors? Why are fossils different colors? Here is an explanation of why fossils and shark teeth are different colors
Modern shark teeth are white; recent shark teeth have white roots and white enamel. So why are fossil shark teeth different colors? In fact why do fossils come in many different colors?
Colors of Shark Teeth: The Simple Answer
The color of a shark tooth, or any other fossil, is determined by the type of sediment the fossil is preserved in.
The color has almost nothing to do with the age or type of fossil.
To elaborate, let's take a basic look at the fossilization process for shark teeth:
Let's say a particular shark tooth is shed and sinks to the bottom of the sea. To become a fossil, it is quickly buried by sediments. Over time, the oxygen poor sediment layers build up and up. Pressure will start to compact the sediments that the shark tooth is entombed in. When enough layers and pressure build up, water will cause minerals in the surrounding sediment to flow into the shark tooth (permineralization). Eventually the minerals will fill in and replace most of the original organic material and the shark tooth will become preserved as a fossil. The color of the minerals in the sediment will become the color of the fossil.
A Megalodon shark tooth found, still in the rock it fossilized in. The rock is a light gray limestone. Notice, the tooth is also the same color. Found at Aurora, North Carolina.
Colors of Shark Teeth: Complicating Factors: A Slightly More Detailed Answer
Now, if you have fossil hunted for shark teeth and other fossils for a while, you will quickly question the above explanation. For example, the roots are sometimes completely different colors than the enamel. Sometimes blue/green teeth are found in gray sediments, white teeth can be found in brown sediments. Some shark teeth look polka dotted, and others have weird colored streaks in them. Obviously, more is going on than in the simple explanation above. Let's go into a little more detail:
Roots vs Enamel - Why are shark teeth roots and enamel often different colors?
Shark teeth enamel are made of a completely different substance than roots and bones, so they have a very different chemical composition. The difference in chemical composition makes them react differently to mineralization, which causes the differences in color.
Why are all the fossils in a certain formation or even the same layer not the same color?
Sometimes, like in Aurora, you can look in a light gray layer and find yellow/green teeth. Why they are not all the same color as the layer?
It's all in the chemistry. The exact types of sediments react differently to the fossils. Clays are different than sands and silts, which are different than limestone. The properties of a sediment such as organic rich vs organic poor, the PH balance (from acidic to basic), and even the size of the sediment grains, all react differently to the fossils. These different mineral replacement reactions all affect the final outcome of the fossil color.
Besides for the actual fossilization process, there are a multitude of other factors that can affect the color of a fossil after fossilization.
If a fossilized shark tooth is in sediment has ground water running through, the water will leach the minerals back out of the fossil and cause color changes, making the colors lighter. Sometimes only part of the fossil is leached. In some cases, a fossil can look white again, like a modern tooth.
A white Megalodon shark tooth. Most of the color has been leached out by ground water.
There are a wide range of other post fossilization factors that can change the color of a fossil. For example, cracks in the sediment running along the fossil, plant roots and animal burrows against the fossil, and even different sized substrates other than the normal sediment lying against the fossil can change the color on parts of the fossil. These complicating factors, and others, can give the fossil a beautiful multicolored appearance; it can give them a cloudy, speckled, and even a streaked appearance.
Notice the speckled and cloudy patterns on these teeth. The center orange angustidens tooth has a white lightning type pattern running up the right side of the root and enamel.
Examples of Shark Teeth Colors from Different Types of Sediments
Mix of Gray / Blue / Green / Brown
Many layers in the famous Calvert Cliffs consists of Bluish and Greenish clays, mixed with brown sands and iron. Fossils shark teeth from these layers tend to have a mix of these colors, with dabs of brown, blue, and green
Mix of Red / Orange
The Cretaceous shark tooth bearing formations in New Jersey are full of iron oxide, or rust. This gives the shark teeth and other fossils a red / orange color.
The Peace River formation in Florida is chalk full of phosphate, a dense, black mineral. The fossils here are often a black color.
Black or Brown
The coastal rivers in South Carolina contains tannins. This gives the rivers a characteristic dark brown color (Blackwater Rivers). The fossils from these rivers absorb these tannins and are often a dark brown color.
Mix of Gray / Yellow
Fossils from the Pungo River Formation at Aurora, North Carolina have high concentrations of Phosphate preserving them. However, the limestones and other sediments are a gray color, giving the fossil shark teeth a beautiful grayish yellow collor.
These are Authentic Megalodon teeth sold by Fossil Era , a very reputable fossil dealer (that I personally know) who turned his fossil passion into a business. These Megalodon teeth come in all sizes and prices, from small and inexpensive 2 and 3" teeth to muesum quality 6+" teeth. Each tooth has a detailed descriptions and images that include its collecting location and formation. If you are looking for a megalodon tooth, browse through these selections!
Great Introductory Fossil Books:
DK Eyewitness Books: Fossil This book is a great introductory book about fossils. It explains what fossils are, how fossils form, and how they lived. It is chalk full of spectacualr images of all kinds of fossils, and give the history of fossil discoveries. It's a must have book for any fossil enthusiast. This book is, again, a great resource book. It has a 34 page identification section in it!
Fossil Shark Teeth of the World, A Collectors Guide This Shark Tooth book is a pictorial book of many of the fossil shark teeth of the world! It's great if you are just getting started into fossil shark teeth. The organization makes identifying shark teeth and learning about them very simple.