How Old Are Shells That You Find on the Beach?

Sea shells have existed for millions of years, ever since the first mollusks roamed the earth. And unlike animals with definite signs from which we can tell their age, sea shells come in unique shapes, designs, and colors, making this judgment much harder. However, as an avid shell collector, it’s normal to stroll along a beach and wonder how old the sea shells are, so how can you tell?

Some shells you find on the beach may be hundreds of years old, while others may only be a few weeks old, depending on the shell species and where you find them. It’s nearly impossible to figure out the exact age of a seashell, but there are ways to approximate its age.

While finding sea shells on the beach is relatively easy, it can be challenging to distinguish between old and fresh shells. This article will give you a better idea of how old shells are and how to tell the age of a sea shell, along with a few factors that affect guessing the age.

Determining the Age of a Sea Shell

Shells come in various shapes and sizes, and it’s easy to assume that giant shells are older than tiny ones, but this isn’t always the case. Sometimes, a mollusk may have better access to resources like food and certain minerals and grow larger than others without access to the same resources.

And as a mollusk gets bigger, its shell expands to accommodate the creature. Additionally, the animal that lived in the shell may already be dead for weeks or even years, making it hard to tell the exact age.

Carbon dating and specific scientific methods can give some information, and researchers have been able to approximate the age of a sea shell somewhat using these techniques. However, old and new carbon exposure can make it difficult to tell the age of a shell, so this isn’t always the most reliable method. 

And if you’re a collector, you probably won’t have access to scientific equipment, considering how expensive it is. Fortunately, there’s another way to guess how old a sea shell is, which may yield surprisingly accurate results. All you need is a few things, including:

  • One magnifying glass.
  • Some measuring tape.
  • A standard calculator.

So, how can the average collector determine the age of a seashell? You can follow some simple steps to guess the age of the shells you find on the beach. Let’s look at how you can do this next time you find some seashells.

Count the Ridges on Seashells to Guess their Age

When you pick up a sea shell on the beach, you will notice ridges or thin indentations along its surface. While these markings aren’t immediately visible, the magnifying glass will help you see them. But, of course, the ridges on certain shells, like oysters, can be very difficult to spot.

When you see the ridges, begin counting them from the bottom up. Finding the exact amount of lines is where the magnifying glass can be quite handy, so you don’t lose count. But if you count over a hundred ridges, consider using a different method to allocate the number of ridges for efficiency.

Use Math and Approximations to Guess the Age of the Seashell

There are ways you can save time while getting an idea of how old a seashell is. Let’s look at how to use math and some simple tools to guess the age of the shell: 

  • First, measure the length of the hundred you counted and write it down. 
  • Now calculate the length of the entire shell, subtracting the first measurement you got for the hundred ridges. 
  • Then, multiply this number by 100 to approximate the rest of the ridges on the shell.
  • Once you have the total number of ridges (the measured portion plus the first 100), multiply it by 365 to get an idea of the age of your sea shell.

This method gives you the age with some accuracy because scientists have found that most mollusks grow a new ridge approximately per day. So if there are 365 ridges on your sea shell, it’s about a year old.

Remember, though, that this method won’t give you an exact number but an estimate of how old the shell is. For example, the mollusk living in the shell may have died a while back, and the shell may be lost at sea for months or years before you spot it on your walk along the beach.

As such, you can never tell the exact age of an empty shell on the shores because no one knows precisely how long since the mollusk lived in it.

Factors That Determine a Sea Shell’s Age

As mentioned above, counting ridges won’t give you an entirely accurate estimate of a shell’s age. The mollusk may have abandoned the shell or died. In either case, the exterior stops growing ridges and may float around for a while.

While counting ridges can give you an estimate, and you might even get close, other factors affect the age of a sea shell. Here are a few other things that can make it difficult to determine the exact age of a sea shell you find on the beach.

Environmental Factors  

There’s no way of telling exactly when the mollusk dies in its shell, making it impossible to predict the precise age. However, aside from this factor, the shell’s immediate environment also affects how old it may look.

For example, while people have found clams that can be dated back decades, scientists have found a clam over 500 years old. However, it’s not common to discover many clams that live for a century or more, as very few live for multiple centuries. 

The interesting thing about this discovery is that the clam was found off the Icelandic coast, where the water is frigid and contains certain minerals not found elsewhere. This discovery is also significant as scientists have found multiple clams in the same zone since then that date back over a century.

The Irish and North Sea may contain certain minerals or provide the right temperature for these clams to survive and retain their shape for longer.

Conversely, scientists also found that waters with frequent temperature changes and seas below ozone depletion areas impact the age of shell loss. The shell changes because it can’t retain its shape in such conditions as they lose calcium content. 

As such, it’s rare to find shells of advanced age in locations with extreme temperature swings. So, while counting ridges may help you figure out a shell’s age, the conditions it lived in will determine how old it can grow.

Certain conditions, like those on the Icelandic coast, can enable this longevity and slow down the aging process in shells. As such, you can expect to find shells of different ages depending on the beach you’re searching; some may be very old.

Shell Species 

The kind of shell you’re dealing with influences how old it can get when left without an animal. Cuttlefish shells are fragile and won’t survive long when left on the shore. The shell will begin to disintegrate within a few weeks and may be gone entirely in a year. If you find a cuttlefish shell while scouring the beach, it’s unlikely that the shell is older than a year. 

On the other hand, scientists found an 18,000-year-old conch shell that was used to play tunes, and that’s still in pretty decent shape. It’s believed that these conches are the shells of various snails living on the ocean floor. They tend to be longer-lasting than the shells of most other mollusks.

Determining the exact age of a shell may be impossible, but trying to gauge how old it is can be an exciting activity in itself. So any time you return home with a bucket of sea shells, be sure to clean them properly before you use them or set them up at home.

To clean the shell, you simply need to follow these steps: 

  1. Bleach the shells to remove the outer skin.
  2. Rub with vinegar solution to get rid of bacteria.
  3. Boil or freeze them to get rid of animal tissue.
  4. Shine with mineral oil for a shiny look.

Etiquette When Determining How Old Shells Are

If you find a shell with a living creature, it’s best to return it to the ocean where it belongs. You don’t want to remove a mollusk from its natural environment because it’s part of the natural ecosystem.

In addition, many beach authorities advise guests against picking up shells and taking them home. While it may seem harmless, removing one of these mollusks from its natural environment can negatively affect the entire marine ecosystem. Check local regulations before collecting shells, even if they’re empty.

Final Thoughts

Figuring out how old sea shells are is still a bit of a mystery. And while you’ll never know the exact age of a shell, the uncertainty makes collecting and studying them exciting!

By following a few simple steps, you can have a pretty good idea of how old a shell is before adding it to your collection.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to tips on finding and collecting precious items. Inspired by reading countless adventurer reports from the oldtimers, Alex is passionate about discovering hidden treasures and loves to share his experience with the rest of the world.

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