How to Hunt for Geodes
A geode is a type of agate (usually) which has a hollow interior. When you pick up an agate that hasn’t been opened, it will generally feel lighter in weight than another stone of a similar size and composition.
You have likely seen cut geodes for sale at mineral shops. They usually look like half a rock with one flat side containing concentric bands of color surrounding a hollow cavity.
The hollow cavity may have crystals growing on the inside edges. The outside part of the geode, however, is typically quite drab and dull, and looks like any other rock.
How to Identify Geodes in the Field
- Start out by searching in a location likely to yield geodes. You can walk into ranger stations and welcome centers and often find guides to rock hunting in your area. The guides may contain information about where to find geodes based on other rock hunters? experiences. These guides are often free for you to take.
- Geodes are often rounded, though not perfectly. Some have more of an oval shape. It is very rare for a geode to be a sharp, pointy rock. This has to do with the way that geodes are formed. Geodes typically form inside pockets of volcanic rock (the pockets, like the rocks, are generally spherical). A silica gel inside hardens and crystallizes into the chalcedony bands, but runs out before the entire rock can fill in. That’s why there is a hollow cavity inside.
- The surface often has a lumpiness to it. This usually is not too accentuated, but it is generally noticeable. These rocks are rarely 100% smooth on the outside.
- Geodes often weigh less than other rocks which are made of similar materials (so far as you can tell) and have the same basic size and shape. This can be a telltale sign of a hollow interior. Even agates that form this way that are not hollow inside can still be beautiful when you break them open since they may be filled in with the agate bands of color.
Eventually you’ll need to break the rock open to see what’s inside. The easiest, but also the worst way to do this, is probably to throw the rock against another rock or wall. It may split nicely, but it is just as likely to shatter.
Sawing a geode open is probably the best and most reliable way to get a nice clean cut. If you cannot do that, a hammer-and-chisel method is recommended. This is also the most common approach to opening a geode, since saws for this purpose are specialized and not many people own them.
A standard flat-faced chisel and hammer will work fine. You must first score the geode’s circumference where you want the break using the chisel. Only once you see a crack developing along the line you want should you follow up with the hammer and break it gently open.
You must be patient when you break open your geode, or you may find yourself with a shattered result, just like you would if you threw it against a rock or wall. The chisel-and-hammer method is very reliable, but only if you take your time and do it right.
Once you get your rock open the right way, you may find yourself rewarded for your patience when you discover that you have unearthed a beautiful geode!