Ever since I started rockhounding I have wanted to find the elusive geode.
I’ve seen geodes in the gem and mineral collections of museums, cut open and displayed on fine black velvet with single source dramatic lighting, looking for all the world like a secret place that existed, hollow, with its own aesthetic rules.
And I’ve seen geodes displayed at the shows where people bring their most spectacular finds, polish them up, and offer them for sale.
But I have never located a geode in the wild, and, having opened it up, become the first person to see the delicate filigree of minerals and banding hidden inside.
There are three main types of rocks in the rock cycle: sedimentary, igneous and metamorphic. Geodes can be found in the sedimentary and igneous rock types. Sedimentary rock is the result of eons of organic and inorganic material precipitating and settling and compressing into rock. Igneous rocks are the result of volcanism. Both types of action can result in gas bubbles being formed and trapped inside of solid shells. If the walls of the shell are permeable, water bearing minerals can penetrate and even more minerals can precipitate out of solution and grow into crystals.
Sedimentary geodes are generally easier to get into. They might have a thin limestone layer covering and break open at the tap of a hammer and chisel. Igneous geodes are formed in silica rich rhyolite lava and are called thundereggs. The best way to open them up is with a diamond bladed saw. Both types of rocks can have very ordinary, dull or even ugly exteriors, although the volcanic type may have quartz “windows” on the surface hinting at what exists inside.
Geodes can range in size from not much bigger than a grain of rice dug in some volcanic basalt to the legendary Pulpi Geode. Discovered in 1999 in an abandoned silver mine in Pulpi, Spain, the Pulpi Geode is located 160’ underground and measures 26’ by 6’ wide by 5’6” high, and, yes, tours are allowed in.
The essential book for amateur collectors and rockhounders looking for places to explore is “Gem Trails of Arizona” by James R Mitchell. Published in 2009 by Gem Guides Book Company, it lists 104 collecting sites from extreme southeastern California to extreme southwestern New Mexico, with the bulk of the sites located within the borders of Arizona.
Site #85 is entitled “Geronimo Trail Geodes.” Geronimo Trail runs from Douglas, Arizona to Animas, New Mexico a distance of approximately 80 miles. It is rugged and remote. A portion of the road runs through the Coronado National Forest and the Peloncillo Mountains. Along a seven mile stretch of the road, beside the Clanton Draw, there is an area in which thundereggs can be found and collected.
A recent day-long trip yielded a beautiful drive out of Douglas. Underneath towering hoo-doos and irregular cragged peaks of red and yellow and orange, the Clanton Draw is a skinny greenway loaded with wildflowers that snakes along the road on its way to draining out into the Animas Valley of New Mexico. We gathered several pounds of egg-shaped agates and brought them home.
Getting to the heart of something that is hard as rock does require a specialized tool. For me it meant the purchase of the Hi-Tech 10” Lapidary Equipment Slab Saw. Tiny diamonds are embedded in the saw’s edge so the blade is smooth to the touch and not sharp at all. Technically you are polishing your way through the rock.
When I first watched YouTube videos of people using these saws I thought that they were acting quite foolhardy, pushing one-inch diameter stones into a fast turning blade with their bare hands. Then I watched a short video produced by a guy who goes by the name Michigan Rocks. The title of his video is “You’ll Cut Your Finger Off On That Rock Saw!” In it he pushes a slab of stone into the spinning blade with one hand while a finger from his other hand rests on the cutting edge.
After he completes the cut through the rock he holds up the finger that has been contacting the blade and, voila! No injury. He does caution that there is another type of rock saw blade that has the diamonds electroplated on the outside of the blade as opposed to embedded and that type will definitely cut you.
For the record I still have not made contact with the blade while it is running and I don’t intend to do so.
A few days after my saw arrived my son visited and set it up for me. I still felt like a novice so I delayed making any cuts; instead, I watched more YouTube videos made by people who seem to have a real knack for picking out just the right rocks for cutting and pushing them into the saw blade in just the correct manner to produce spectacular results.
When I finally cut into my first thunderegg I was at first pleased that the sparks, grinding sounds, and flung water came to an end after about 30 seconds and I still had all of my digits intact. I was disappointed though when I looked and saw a solid core of hardened quartz. No geode. Very little banding.
Rocks #3 through #5 yielded similar results. I was beginning to doubt that I had collected the correct type of rock. Number six though, while looking a lot like the other rocks, at least on the exterior, cut a little quicker. I shut off the saw and let it glide to a stop. I pulled the two halves away and held them up for inspection and woot…there it was. A tiny ½ inch cavity, with several terminated crystals. Not museum or gem show quality but a geode nonetheless.
I am hooked.
Keith Krizan can be contacted at therealkbkkbk@gmail.com