Why Are Shark Teeth Black?

How Black Shark Teeth Work (and How To Find Them)

Fossilized shark teeth are usually black, glossy in the light, and have a pointed shape.
Fossilized shark teeth are usually black, glossy in the light, and have a pointed shape. Cyndi Monaghan / Getty Images

Question: Why Are Shark Teeth Black?

Usually when you see shark teeth they are black, yet teeth in living sharks are white. Here's the explanation behind why shark's teeth turn black.

Answer: Shark teeth are made up of calcium phosphate, which is the mineral apatite. Although shark teeth are sturdier than the cartilage that makes up their skeleton, the teeth still disintegrate over time unless they are fossilized.

This is why you rarely find white shark teeth on a beach.

Shark teeth are preserved if the tooth is buried, which prevents decomposition by oxygen and bacteria. Shark teeth buried in sediments absorb surrounding minerals, turning them from a normal whitish tooth color to a deeper color, usually black, gray, or tan. The fossilization process takes at least 10,000 years, although some fossil shark's teeth are millions of years old! Fossils are old, but you can't tell the approximate age of a shark tooth simply by its color because the color (black, gray, brown) depends completely on the chemical composition of the sediment that replaced the calcium during the fossilization process.

How To Find Shark Teeth

Why would you want to find shark teeth? Some of them are valuable, plus they can be used to make interesting jewelry or to start a collection. Plus, there's a chance you'll find a tooth from a predator that lived 10 to 50 million years ago!

While it's possible to find teeth just about anywhere, your best bet is to search at a beach. I live in Myrtle Beach, so every time I go to the shore I look for teeth. At this beach, most of the teeth are black because of the chemical composition of the sediment offshore. At other beaches, fossilized teeth may be gray or brown or slightly green.

Once you find the first tooth, you'll know what color to seek. Of course, there's always a chance you'll find a white shark tooth, but these are much harder to see against shells and sand. If you've never looked for shark teeth before, start out looking for black pointy objects.

If the teeth are black, there will also be some black shell fragments that resemble shark teeth, How do you know if it's a shell or a tooth? Dry off your find and hold it up to the light. Even though a tooth may be millions of years old, it will still look glossy in the light. A shell, on the other hand, will show ripples from its growth and maybe some iridescence.

Most shark teeth also maintain some of their structure. Look for a cutting edge along the edge of the blade (flat part) of the tooth, which may still have ridges. That's a dead giveaway you've scored a shark tooth. A tooth may also have an intact root, which tends to be less shiny than the blade. Teeth come in a variety of shapes. Some are triangular, but others are needle-like.

Good places to start are at the waterline, where the waves can help reveal the teeth, or by inspecting or sifting through a pile of shells. Keep in mind, the size of the teeth you can find is usually similar to the size of surrounding debris.

While it's possible to find a giant Megalodon tooth in the sand, large teeth like this are most often found near similar-sized rocks or shells.