Breaking open geodes (without destroying them!)

I always seem to get calls from people asking “How can I open a geode without breaking it into small pieces?” Well, there are several ways, some good and some not so good. Here, I will describe four of the most common ways. [By the way, it’s a good idea to use safety goggles whenever you start banging away at a rock.]

1) Diamond Saw – If you are lucky enough to have a large diamond saw or know someone who has one, you can see the geodes in two. This works best when there is a vise to hold the sample. You can cut the geode open and end up with two halves with a smooth face on each. (But not everyone has a diamond saw …)

2) Another method of opening geodes that works well (the method I use most often) is opening the geode with an old cast iron plumbing pipe cutter. This is a tool that plumbers used to do home plumbing when working with cast iron plumbing pipes. (Houses built before about 35 years ago.) I have one of these tools that I use to open geodes and most of the time I can break it into two equal halves. This really does a good job.

You may have seen show merchants who were opening geodes with one of these tools. The tool has a chain on the commercial end with links like a bicycle chain, and on this chain there are round carbide rollers with sharp edges.

To open the geode, simply wrap the chain, with the carbide rollers, around the geode, fix it in a notch in the tool and press the handle down. This contracts the chain around the geode evenly in all directions and tightens down to where the geode breaks and opens into two halves. I got my cast iron plumbing pipe cutter from a retired plumber here locally. If you are going to break a lot of geodes, you may want to get one.

3) Hammer and chisel. Most people don’t have a diamond saw or plumbing cutter, and they just want to break a couple of geodes. Well, you can do a good job with a hammer and chisel. I have done it several times and it works fine. Take your hammer, chisel, and geodes outside where there is a concrete path, driveway, steps, etc. – in other words, a hard surface. I would not test it on a wooden surface. And you almost need three hands to do this. Place the geode on the concrete and hold it by the sides with one hand, then hold the chisel on top of the geode and tap it LIGHTLY with your hammer. Don’t try to open it now … Rotate the geode about half an inch, place the chisel in line with where you just hit it, and hit the chisel again … LIGHTLY. Do this around most of the geode. By the time you have struck the chisel in a line around the geode, it should be ready to open. If the geode has not opened at this point, start around the circumference again, tapping the geode with the chisel in a straight line. Hit the chisel a little harder this time. This is a bit slow, but if you do it right and don’t rush too much, you should be able to break the geode into two halves that you can put back together where you can’t tell where it is. It was broken.

4) Hammer: Of course, you can hit the geode repeatedly with the hammer until it opens, but it will most likely end up in a few pieces. It is not a good method!