Lots of rockhounders ask how to open a geode. The easy answer, of course, is to have the geode opened for you. A professional (well, okay, someone who does this regularly) will have the right equipment, know what they are doing, and usually get a better result than you might expect on your first geode. But, you really want to open a geode and, as a result, professional help is out of the questions. Okay.
Opening A Geode
Opening a geode – and maximizing your chances of a good result – is a multi-step process.
1: Start with a geode. Seriously.
Thunder eggs, for example, are not usually hollow and, as a result,
don’t ‘crack in half.’ They get
destroyed. You will want to begin with a
2: Try to start with a hollow geode. Two reasons.
First, solid or nearly solid geodes are more difficult to crack in half
than a hollow geode. Second, and more
important, if the geode is not hollow, there will be significantly less
opportunity for the geode to include well formed crystals. You might be wondering, how can one know
whether the geode is hollow? If it
‘rattles’ when you shake it, it’s probably hollow. If it’s lighter than another similar sized
geode, it’s probably hollow.
- Step 3: Safety. Breaking rocks and cracking geodes can be dangerous. A small chip from the rock (or a hammer) can cause injury to anyone in the area. Use proper safety gear (including, at a minimum, eye protection) and make certain that you are not endangering others.
4: Equipment. Use equipment designed for breaking
rocks. There is a big difference, for
example, between a geologist’s rock hammer or a crack hammer and cold chisel
and a standard framing hammer and screw driver or wood chisel. One set of tools actually is designed and
made to hit rock; the other is not.
- Step 5: Choose A Method. Listed below are the most common methods for cracking open a geode. Sadly, the least expensive method also usually gets the worst results. That’s why the professionals charge you to open a geode.
Possible Methods to Crack Open A Geode
- Hammer: It’s possible to crack open a geode with a crack hammer or a geologist’s rock hammer. This, clearly, is the easiest, least expensive method. Simply place the geode on a firm wood board (not your concrete garage floor … because, guess what? Yep, rocks and crack hammers can break, chip, or damage concrete) and hit the geode in the center. The geode will open. Generally speaking, however, you are not likely to get spectacular results. It will be rare to get the geode to crack open neatly in two pieces and without damaging the interior crystals, if any. But, it is quick and easy.
- Sock & Hammer Method: Place the geode in a sock and, with only being able to see the lump in the sock, try to hit the geode with a rock hammer. This method targets two situations: (1) children who want to open a geode (and adults who are nervous about someone getting hit by a rock chip); and (2) small geodes. The sock is designed to reduce the risk of injury. This approach is quick and easy, but your odds of getting an evenly cracked, undamaged geode are low.
- Hammer & Chisel Method: Unlike the hammer method, which, in essence, crushes the geode – lightly or firmly – and hopes for the best, this method is designed to try to improve the odds of opening the geode in approximately equal halves. To do so, use a rock/crack hammer and flat-blade stone chisel (not a wood chisel; not a screw driver; not an ice pick; not a pointed chisel) to ‘score’ a line around the circumference of the geode. Once you have a line all the way around the geode, go around again. The idea here is to lightly chisel a path to increase the chances that, when the geode breaks open, it will do so on the chiseled line. This process will take some time. If you lose patience and just whack the geode, well, you might as well have used one of the methods above.
- Saw Method: Geodes may be cut open with a mechanical rock saw. [Note: there are non-mechanical hand-powered ‘rock saws’ that you can buy. We don’t use these. You’re cutting a rock … a hard rock … you’re going to want a real tool.] If you don’t have a rock saw (lapidary saw) with an actual lapidary blade designed to cut rocks, some commercial rock shops will cut a geode (or other specimen) for you for a small fee (rock saw blades are not inexpensive). Alternatively, a standard mechanical tile saw (the kind used for cutting flooring/bath tile or granite counters) also works (the cut surface may not be quite as smooth as a professional grade lapidary saw). Tile saws often may be rented from commercial rental businesses or large home improvement stores. You may have to buy a blade, which means this is usually a better option if you are going to cut more than one geode (for example, a scouting or school project). The big advantage of a mechanical saw is that the geode may be cut in equal halves and not end up as a pile of ruble. The disadvantage is that, using a saw may cut through or damage nice internal crystals (a hammer may do that as well). In addition, both rock saws and tile saws can be messy (they are liquid cooled and, although rock saws sometimes have protective enclosures, tile saws typically do not – the wet dust (slurry) does spatter around.
- Soil Pipe Cutter Method: Geodes may be cracked open with a soil pipe cutter. Soil pipe cutters are available is a variety of styles, including mechanical and non-mechanical. You will want a soil pipe cutter that has a log handle (for leverage) and a chain similar to a bicycle chain but that has sharpened carbide-tipped roller blades. The chain is wrapped around the geode and, when pressure is applied, because the chain focuses force all the way around the geode in a line, the geode often cracks open neatly. The advantages of this method is that it is quick, clean, and often has good results (that’s why this method often is used by geode vendors at larger rock shows). The disadvantage, of course, is that most folks do not own a soil pipe cutter and this tool is rather expensive. Occasionally, they are available for rent.