Why Shark Teeth Are Different Colors (The Basic Explanation)

The color of a fossil shark tooth is determined mainly by the type of sediment it was buried in. In fact, the color of a shark tooth fossil usually has almost nothing to do with its age or the species of shark. This is why fossil shark teeth can be black, red, blue, brown, gray, or even white, depending on where they are found. However, one color is far more common than all the others: black. Most fossil shark teeth are black because they are usually preserved in sediments that are rich in phosphate.

So why do shark teeth turn black in the first place? When a shark sheds a tooth, it sinks to the bottom of the ocean and becomes buried in sediment. In many fossil shark tooth layers, the sediment itself is full of tiny phosphate grains or small phosphate pebbles. Over time, water carrying dissolved minerals, such as phosphate, moves through the sediment and into the tooth during the fossilization process.

As this happens, the minerals in the surrounding sediment slowly replace much of the original material in the tooth. Because phosphate is so common in many fossil-bearing formations, the tooth often takes on a dark black color. This is why black is the most common color of fossil shark teeth found around the world.

However, phosphate is not the only mineral involved. Other minerals in the sediment can also seep into the tooth and change the color. Iron-rich sediments can turn shark teeth red, orange, or brown, while other minerals can produce blue, gray, green, or even white fossils. So although most fossil shark teeth are black, the final color always depends on the minerals in the sediment where the tooth was buried.

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Why Fossil Shark Teeth Are Not Always the Same Color (Roots, Enamel, and Other Factors)

If you have spent any time fossil hunting for shark teeth, you have probably noticed that the simple explanation does not always seem to fit. Some shark teeth have roots that are completely different colors than the enamel. Blue or green teeth can sometimes be found in gray sediments, and white teeth can appear in brown layers. Other teeth may look speckled, streaked, or even polka dotted. Clearly, more is happening than just one mineral turning the entire tooth the same color. Let's look at the reasons in a little more detail.

Why are shark tooth roots and enamel often different colors?

The enamel of a shark tooth is made of a very different material than the root. Because the chemical composition is different, the enamel and the root react differently during fossilization. Minerals may replace the root more easily than the enamel. This is why fossil shark teeth are often two different colors, especially black roots with lighter enamel.

Why are fossil shark teeth in the same layer not the same color?

Even when shark teeth are found in the same formation or the same layer, they are not always the same color. For example, in Aurora, North Carolina, you can search a light gray layer and still find yellowish-green shark teeth. The reason is chemistry. Different types of sediment react differently with fossils. Clay behaves differently than sand or silt, and limestone reacts differently than both.

Other factors also matter. Organic-rich sediment reacts differently than sediment with very little organic material. The pH of the sediment, whether it is more acidic or more basic, also affects how minerals replace the original tooth. Even the size of the sediment grains can influence the final color. All of these small differences help explain why fossil shark teeth can vary so much in color, even when they are found right next to each other.

Color changes after fossilization (groundwater, tree roots, and other factors)

The color of a shark tooth is not always fixed once it becomes a fossil. In many cases, the color can change after fossilization due to conditions in the surrounding sediment.

How groundwater can change the color of shark teeth

If groundwater flows through the sediment where a fossil shark tooth is buried, it can slowly remove some of the minerals from the fossil. This process can lighten the color of the tooth over time. Sometimes only part of the tooth is affected, which can make the root and enamel different colors. In some cases, a fossil shark tooth can even become white, or light colored again, and resemble a modern tooth.

Other reasons fossil shark teeth can have streaks, spots, or unusual colors

There are many smaller factors that can also affect the color of fossil shark teeth. Cracks in the sediment, plant roots growing near the fossil, and animal burrows passing through the layer can all change how minerals reach different parts of the tooth. Even small changes in the surrounding sediment can produce color streaks or spots.

These factors help explain why some fossil shark teeth have a multicolored appearance. Others may look cloudy, speckled, or have lightening and streaked appearances. All of these variations are normal and are part of the fossilization and post-fossilization process.

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Why Shark Teeth Are Different Colors in Different Locations (Real Examples from Famous Fossil Sites)

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Fossil Shark Teeth from Calvert Cliffs, Maryland

At the famous Calvert Cliffs in Maryland, many fossil-bearing layers consist of bluish and greenish clays mixed with brown sands and iron-rich sediments. Because of this combination of minerals, fossil shark teeth from Calvert Cliffs are often multicolored. It is very common to find teeth with a mix of blue, green, gray, and brown tones all in the same tooth.

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Fossil Shark Teeth from the Big Brook area of New Jersey

In New Jersey, many of the Cretaceous shark tooth formations are rich in iron oxide, which is essentially natural rust. This iron gives fossil shark teeth and other fossils from these layers their well-known red and orange colors. That is why shark teeth found in New Jersey are often bright red, reddish-brown, or deep orange.

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Fossil Shark Teeth from Venice Beach, Florida

The Peace River formation in Florida is extremely rich in phosphate, which is a dense black mineral. Because of this, fossil shark teeth from the Peace River are most commonly black. The Venice Beach collecting area and the Peace River collecting area are both well known for producing large numbers of black fossil shark teeth.

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Fossil Shark Teeth from Coastal South Carolina

The coastal rivers of South Carolina are known as blackwater rivers because they contain high levels of tannins from decaying plant material. These tannins give the water a dark brown color, and fossil shark teeth found in these rivers often absorb that color. As a result, shark teeth from South Carolina rivers are frequently dark brown or almost black.

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Fossil Shark Teeth from Aurora, North Carolina

Fossils from the Pungo River Formation at Aurora, North Carolina are preserved in sediments that contain a lot of phosphate. However, the surrounding limestones and other sediments are usually gray. Because of this combination, fossil shark teeth from Aurora often have a distinctive grayish-yellow or gray-tan color that is very different from the deep black teeth found in Florida.

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Conclusion: Why Shark Teeth Are So Many Colors

The color of a shark tooth fossil is not determined by its age or even the species of shark: it is determined almost entirely by the minerals in the sediment where it was buried. Iron can turn shark teeth red or orange, phosphate often turns them black, and other minerals can create blue, green, gray, brown, or even white teeth. Differences in chemistry, groundwater, and the fossilization process can also cause the roots and enamel to be different colors or give teeth streaks, spots, and unusual patterns.

So if you have ever wondered why shark teeth turn black, the answer is simple: the minerals in the surrounding sediment replaced the original material in the tooth. That is why shark teeth from different locations around the world can look completely different even when they are the same species and the same age.

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FAQs: Shark Teeth Colors

• Q
  Why are most fossil shark teeth black?
  A Most fossil shark teeth are black because they are preserved in sediments rich in phosphate. During fossilization, phosphate minerals seep into the tooth, replacing organic material and giving it a dark black color.
• Q
  Can fossil shark teeth be other colors besides black?
  A Yes, fossil shark teeth can also be red, orange, blue, gray, brown, or even white. The final color depends on the minerals present in the sediment where the tooth was buried, such as iron oxides for red/orange or tannins for dark brown.
• Q
  Why are the roots and enamel of shark teeth sometimes different colors?
  A Shark tooth enamel and roots are made of different substances with different chemical compositions. They react differently to mineralization, so roots and enamel often end up different colors during fossilization.
• Q
  Why aren't all fossils in the same sediment layer the same color?
  A Even within the same layer, different sediment grains, PH levels, and organic content can react differently with fossils. This causes individual teeth to take on varying colors, patterns, or streaks despite being in the same layer.
• Q
  Can fossil shark teeth change color after fossilization?
  A Yes, factors like groundwater can leach minerals out of a tooth, making it lighter or even white. Cracks, plant roots, animal burrows, and contact with other substrates can also create streaks, speckles, or multicolored effects.

Shark Teeth Colors FAQ

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