Chisels are a necessary tool for those involved in hard rock mining, and they’re a welcome companion on most other rockhounding trips. You can use them to carefully unearth your treasures, and even to crack open geodes cleanly if you give it a bit of care.
But there’s a lot more to a chisel than meets the eye. One of the key differences you’ll need to know is whether you need a cold chisel or a regular chisel.
So, let’s get to it!
What is a Regular Chisel?
A chisel seems like a simple tool to most. They’re usually made with a bar of iron or steel and come to a point, the fancy ones might even have handles!
There’s more to it than that. Chisels are a tool designed for use in a very wide variety of materials, but some are better suited for different purposes than others.
The hardening process for a chisel is extensive, and one of the most important parts of it’s construction. Steel is a very versatile material, and when steel is heated to the correct temperature and quenched it becomes very hard.
Afterward, the chisel is tempered by reheating it and slowing down the cooling. This helps align the internal crystalline structure of the steel and creates some “give” that makes the chisel tougher.
Most regular chisels are created with some variant of tool steel.
Chisels designed specifically for harder materials sometimes have a bonded tip created from a harder metal. The most common tip for rock chisels is created using tungsten carbide, an extremely tough metal that’s actually harder than most minerals.
Tungsten carbide hits a 9 on the Moh’s scale, making it significantly harder than anything most rockhounds will encounter.
A “regular” chisel generally refers to common woodworking chisels, which aren’t suitable for any work with metal or stone. With that in mind, we’ll be referring to tungsten carbide-tipped chisels as “regular chisels” or “rock chisels” to contrast them with cold chisels.
What is a Cold Chisel?
Cold chisels are sometimes used in place of more expensive, specialized chisels. Their actual use is where they get their name, a cold chisel is used to cut metals at room temperature.
Cold chisels have a less sharp angle than more specialized chisels. This less acute angle is great for rough-cutting metal, but it’s not ideal for precisely breaking stones.
Cold chisels come in a few shapes, but the main one of interest here is a “flat chisel” which just has a broad line for an edge.
Cold chisels are tempered, making them a bit softer but tougher than most hardened steel. This allows them to deform instead of shatter in many cases. This can require a bit of maintenance, but a grinder or file will allow you to fix any deformation.
As a general rule, cold chisels are not great for rockhounding. They’re designed for metal and do their best with their intended material.
That said, they do have their place in the field if you’re aware of their limitations.
I primarily rockhound in areas where I encounter limestone as the matrix. There I can use cold chisels freely to break down anything I come across. The situation is totally different when we’re talking about cutting into metamorphic or igneous stones.
Know where you’ll be digging and you’ll be able to make better choices about your tools over time. Cold chisels are cheap and a great way to start in some areas, but they’re not going to cut it if you’re breaking down pieces of granite and basalt all day.
What Are the Key Differences?
The biggest difference between a regular chisel and a cold chisel is the tip. You can pound hardened carbide into 95% of the rocks on earth without any fear of deformation. They can still shatter, but it’s not a problem you’re like to run into.
Cold chisels, on the other hand, have to be used carefully on stone. Even those intended for concrete or masonry may not be up to the task, rock is tough. They can still be used with softer stones, especially if you exploit natural features to crack them.
It’s tempting to go out only equipped with cold chisels. They’re much cheaper after all. And you may be able to get away with it, depending on your planned area and the stones you’ll encounter there.
When it comes to rockhounding, we can compare them as follows:
|Ideal Material||Stone||Masonry and Metal|
|Tip Material||Carbide||Tempered Steel|
Maintaining either type of chisel is relatively easy in most cases. Cold chisels can be fixed with a good file or grinder with a standard wheel. They tend to deform rather than chip, and you can work the tips a bit if you know anything about forging.
If you don’t, just use a file or grinder and restore the original angle.
Carbide chisels require a diamond tool to clean the edge up. While most people use grinding wheels, I’ve found a set of lapidary files does the job quickly and with less of a hassle. Your mileage may vary.
The key difference here is that a cold chisel is softer and not meant to cut dense stone. If you’re just looking to crack hard stone… well, you need a rock chisel.
But let’s discuss the real-world differences and what you’ll need now.
Which Type of Chisel Do I Want for Rockhounding?
Let’s be blunt for a second: if you’re planning on doing any serious work in hard rock you want a rock chisel. A good-sized chisel that you can pound into rocks is a great thing in the field. The only reason people don’t use them more is the cost.
That said, many experienced rockhounds carry a few cold chisels in their kit. I’m particularly fond of point chisels, which allow you to exert enormous force in a very small area.
Small flat cold chisels also see a lot of use. Some people are even under the impression that they’re the right kind of chisel for stone. Searching for rock chisels often brings up an impressive array of cold chisels.
And the truth is that a lot of times they’ll work, but their durability is drastically lower. If hit improperly into a hard enough material you can actually break the chisel as well.
I recommend a larger flat carbide-tipped rock chisel and a few smaller cold chisels for a beginner.
The rock chisel can be used for tasks like cutting open geodes or breaking through solid matrix when unearthing crystals and stones. If you’re unsure of how hard something is, always use the harder chisel.
A collection of the following cold chisels can help as well:
- Small Flat Chisel- You can use these to leverage cracks and other flaws in hard stones to reveal the interior. They can also be used in a softer matrix(ie: limestone) like a standard chisel.
- Round Nose Chisel- Used to exert a lot of force in a small area. They can be used to create cracks to leverage with another tool or make precise breaks when needed. Point chisels take some experience to use correctly, but they’re invaluable once the skill is acquired.
- Diamond Nose Chisel- Another chisel made to exert a lot of force in a small area. I prefer to use these to widen cracks in hard stone, tapping carefully along cracks can help widen them so you can exploit the flaws.
See the pattern?
Use your rock chisels for the bulky work, and your cold chisels to exploit existing flaws or create cracks. But, as a general rule, get as many rock chisels to replace cold chisels as your budget can afford.
The truth is that cold chisels aren’t ideal, but they can be enough in many circumstances. The best way to learn is in the field, so grab your safety glasses and give it a shot.