Introduction: Split Limestone to Find Fossils!!

If you are a science geek then the prospect of digging up your own fossils has, at some point, probably excited you. The thrill and excitement of finding, seeing and touching something that hasn't been seen for 50 million years is an incredible feeling.

While there are many different ways to find fossils, you can search in streams and oceans for shark teeth and bones, you can dig in the badlands for dinosaur bones, you can search the world for fossils. But if you're like me, then extra time is not a resource you can come upon easily so here's how I fuel my fossil hunting desires!

Southwest Wyoming is home to an area known as fossil lake. Fossil lake has the richest deposit of freshwater fossils in the world! These fossils are found in the local limestone and are as easy to get to as walking up to a rock and picking it up. In and around Kemmerer Wyoming you can find a number of fossil quarries that, for a fee, will allow you to hunt fossils all day long. Some will even take you on night digs to help uncover pristine, museum quality fossils for the so called 18 inch layer (more on that later). I personally recommend Rick Hebdon at Warfield Fossils. Rick and his crew are great, you can dig the quarry during the day and VIP dig at night. If you have a chance to experience the VIP night dig you won't regret it!

Now that you have access to the limestone, what do you do with it. Because the fossils are hidden in the layers of limestone, you need a way to separate the layers to expose them. That's what this instructable is all about!!

Step 1: What You Will Need to Find 50 Million Year Old Fossils in Limestone.

The first thing you need to find fossils in Limestone is....... Limestone, but not just any Limestone. The very best Limestone is from quarries around South West Wyoming in what's known as Fossil Lake in the Green River Formation. Obviously it's easy to get if you live within a days drive but for most of us, that's not the case. Don't worry we can supply you with anywhere from 10 - 30LBS of quality limestone for your splitting pleasure DIRECTLY from the quarries in and around Kemmerer Wyoming. More on that at the end....

You also need:

- A hammer for splitting. A rock hammer is ideal, between 12-16 oz is fine. 20 oz hammers work well too but may be a little overkill.

- Chisel to separate the layers. The best is a dual beveled thin chisel to gently separate the thin layers of limestone without cracking them. The best chisels are specifically made for this purpose and can be found at You can use a regular chisel found at the hardware store but you need to be careful because they are much thicker.

- Gloves for protecting your digits. Not required but trust me, you will want some. Limestone is heavy with sharp edges and hammers hurt.

- Eye Protection. When chiseling anything, pieces fly off and eventually and inevitably hit your eye.

- Curiosity and Excitement! Splitting limestone for fossils is fun and rewarding. Seeing something that hasn't been seen in 50 million years is quite a thrill!

Kids and adults alike love splitting Limestone and finding fossils. Its a true learning experience and it inspires kids to pursue interests other than xbox and playstation (although there's nothing wrong with either). It's nice to get your hands dirty and experience the world around you!

So lets get started!!

Step 2: Why Limestone?

Now that you have your limestone, hammer, chisel and appropriate safety attire, it's time to start splitting. The process of splitting the stone is actually very easy but doing it right can be a challenge. But why limestone and not any other rocks?

To understand HOW to split it and WHY you're splitting it, you need to know a little about how its formed. Limestone is a sedimentary rock formed by deposition of material (minerals, calcium carbonate, etc..) over time usually in bodies of water. As fish, birds, mammals, bugs, etc die, they fall to the bottom and are covered again by more sediment. Over time, the critters that are trapped can end up as fossils. All that being said, you can easily see the different layers of limestone when you look at it from the side. If you look close enough, you can see spaces that a chisel an fit into to separate the rock layers. Carefully splitting the layers can expose full beautiful fossil specimens!

Different Layers provide different quality of fossils.

Obviously over 50 million years, there are deeper layers of limestone than others in fossil lake. There are 2 layers we are really concerned about. The first layer is what is referred to as the 18 inch layer. The 18 inch layer produces some of the finest specimens in the world. Why? One word, Kerogen. Kerogen is derived from algae that have settled to create layers alternating with limestone. The Kerogen forms a very strong "glue" that holds the layers together. When the 18 inch layer is split, it will split along the weaker, non-kerogen, layers that are not as likely to hold fossils. The split limestone contains complete specimens that can be prepared with special tools to create incredibly detailed fossils.

The second layer is what is called the "split fish layer". This layer of limestone does not contain kerogen so the limestone is weakest in the layers that do contain fossils. When you split this layer, its common to immediately expose fossils. This layer usually does not contain specimens detailed enough for scientific study because of damage from splitting but it's a perfect layer for fossil collectors. This is the layer we will focus on.

I will have another instructable on how to prepare 18 inch layer fossils later.

Here's a few tidbits about the limestone from the green river formation.

- 9 inches of limestone represents about 1 million years!

- Over millions of years, volcanoes erupted spewing large amounts of ash into the atmosphere. The ash layers will show up in the limestone as geologic markers. They are thicker than normal limestone layers and are called tuff layers.

- Volcanoes in what is now Yellowstone National park spewed ash clouds that settled in the lake. This is how they know that the sediment is approximately 50 million years old or early to mid Eocene.

- Organic layers are where you find the vast majority of fossils. These layers are stained different colors which allow visualization of the fossils in the different layers.

Step 3: Lets Start Splitting!!

Enough about the history and formation of fossils at fossil lake, lets start splitting!!

Not knowing exactly where the pristine fossils are makes rock splitting very exciting. It's similar to treasure hunting in area where you KNOW there's treasure so the anticipation of a find is very exciting.

You always want to wear gloves and safety glasses when working with rocks, chisels and hammers.

Start by identifying the different layers of the limestone. As mentioned earlier, fossils will create a "stain" so if you can visualize the stained area of rock you can place your chisel in that area. Push the chisel tip directly in the cleavage between layers keeping the chisel as straight as possible along the line. This will prevent uneven splits or cracked rock.

As the layers begin to separate, you will see an even split along the length of the stone. Proceed slowly to prevent uneven splits or fractures. As the chisel gets deeper into the limestone you will hear a hollow sound as you tap the chisel. This hollow sound generally indicates that the stone is split to the point that you can completely separate the layers. Begin to gently angle the chisel to lift the layers apart. Once the layers are apart you can find your fossils!

Don't expect to be perfect at first. Just like anything else, it takes some practice to become proficient at splitting limestone. You also won't find a fossil with every split but you more often than not, you'll find something and it's ALWAYS exciting!

Once you have a specimen you can do some careful preparation to make it even more presentable but that will be another instructable!

Step 4: Where to Get Fossil Rich Limestone

A lot of you may be saying "that would be awesome but I don't live near fossil lake!". Never fear, out of shear insanity, we had 25 ton's of fossil rock shipped to our location. After realizing that's A LOT of rock we can ship 10 to 30 pounds of rock so you can discover your own fossils! Check it out at:

You can find the best splitting tools at

Don't forget to vote for my instructable if you found it enlightening!

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