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Tuff Nuts to Crack: A Thunder Egg Story

Figure 1: Bulk spillover stone in front of Richardson's Rock Ranch rock shop.
Figure 2: Roadside geology, indeed! Tumultuous ramparts of rock greet you at Richardson's Rock Ranch in Madras, OR.

Prepare yourself & hold on to your butt, because this is the epic tale of how we, Alex Jensen and I, went digging for balls of colored minerals in the ranchy, raunchy, rain-free, reflie*-riddled valleys of central Oregon [Figure 1]. Alex is getting his PhD in biology and was a roomie for the whole month of August. Lucky me, because housemates with good taste in extra curriculars are housemates to have. They move from stranger to former stranger to friend. Before long, they might let you share the addiction of rockhounding as their enthusiasm -or is it tolerance?- grows. Maybe then you can cut and run off into the desert for 26 hours, nine of which you might spend car-singing to killer tunage, and three digging in the August heat for thunder eggs! These angelic, mineral-filled globs of metaphoric rock can host colors, patterns, and gem material like you've never seen. Or mayhaps you have seen. I don't know you. I don't know what you've not seen. No -but really- some places even have precious stones in their thunder eggs! Not this place, but they are out there. This place -pause for exaggerated effect- is the fabled Richardson's Rock Ranch (RRR), located in scenic Madras, OR [Figure 2].

Thunder eggs are a type of geode. Just so you know. Just in case you opened this page expecting manifested greatness in blog form and got something else entirely, because I never simply stated that thunder eggs are basically solid geodes [Figure 3]. They form when roiling volcanic ash, called tuff, is intruded with mineral-rich water or molten minerals. Now, that is my understanding from months of asking around and being told slightly different variations on the definition of a geode versus a thunder egg. Frank, owner of The Crystal Habit rock shop, told me that the kind of tuff that makes up the matrix of these geodes varies by location but behaves the same across the board, and that the process for thunder eggs is slightly different than the process to create hollow geodes (probably why I kept getting different answers to the same question). Here is what my pocket rock guide, Rocks & Minerals of Washington and Oregon, Dan R Lynch & Bob Lynch, 2012, has to say about it:

Figure 3: A thunder egg from the Blue Bed at Richardson's Rock Ranch.

"Thunder eggs are a particularly interesting variety of agate that formed in a completely different geological period than most other agates. Most agate formed within vesicles (gas bubbles) in recently cooled lava (molten rock), such as basalt. Thunder eggs formed within hollow pockets in tuff, a type of rock formed by the solidification of volcanic ash. These pockets were made by the rapid expansion of hot gases, leaving a void that later filled in with a solution bearing silica, the quartz material that forms all agates. As the silica crystallized and layered to form agate, it also adhered to the surrounding tuff, forming a round shell of hard rock surrounding the agate core. Therefore, when thunder eggs are found, they appear only as round rocks. One might think this would make them impossible to find, but in most localities, the tuff in which the thunder eggs formed has decayed to a soft, muddy clay and the hard thunder eggs are conspicuous. Finally, some thunder eggs are hollow, making them geodes."

Now, I adore my pocket rock guide, it has shown me a beautiful side of my new state that would otherwise have gone neglected (probably). However, it doesn't always hit the nail directly on its head. For example, it lists snake skin agate as occurring exclusively in Oregon, and yet I have a handful of samples from the diatomaceous earth pits outside George, WA. That said, this description is fairly comprehensive regarding the thunder eggs we were apt to find last weekend. They are geodes, but they are not always exclusively agate, or so I am lead to believe by the rock market. In any case, these handsome fellas are spherical, lumpy masses of rock with interiors that come in a tantalizing array of layers and colors. In Figure 3, you can see another interesting facet of a thunder egg, its pressure cap. Frank is cutting many of the eggs we brought back from this trip, and while he prepped a geode to be cut, he explained: "There are two primary pressure caps on a thunder egg. You want to find them, and then cut perpendicular to that line, because the edges of the caps are where the material got in and created the bubble. Hopefully, when you do that you find a five-point star, or a nice big cavity with shapes and pictures looking back at you."

Figure 5: One of the owners of Richardson's Rock Ranch, after giving us our map and introductions for digging.

Thunder eggs are not difficult to find if you happen to already be in central Oregon, or outside Ellensburg or Naches, Washington. You could swing a dead cat and hit someone who has gone to dig for thunder eggs, or just so happen to pick some up at one of the many rock shops in the PNW. There are 258 known varieties of thunder eggs in Oregon, and between the RRR area and the Lucky Strike Mine, you could potentially find all of them[Frank, personal communication, 2017]. That said, they are not always easy to extract. Finding the locations is fairly simple, as a rudimentary Google search will lead you to several pay-to-dig mines around Madras and Prineville. Once you get there, however, you might have to make a judgement call as to the amount of effort you want to put in versus the quality of stones you want to walk away with. I subscribe to the idea that, most of the time, you get out of something what you put into it. In the case of rockhounding, what you are putting in is often time, sweat, possibly blood, and lots of emotional energy whilst on the hunt for new and attractive rocks and/or ways to use them.

FACT ALERT! Madras was recently known for its booming population swell, as almost one million visitors poured in to catch a two minute glimpse of the 2017 total eclipse. Heard it was pretty intense with people in tents (that doggerel of a joke makes me feel dirty, but I'm hoping it might dig into someone's funny bone and fester there as a weak chuckle). After you drive to Madras (it took us 4.5 hours), you may need to camp lakefront of a lovely desert oasis [Figure 4]. The best times to dig are generally in the morning, before it gets too hot, so be sure to set your alarms and get there as close to when RRR opens as you can. It opens at 7am. Also, sometimes, there are lots of people later on, and nobody wants to feel rushed by a crowd when they're coaxing a tasty little thunder eggie from its holy resting tuff. Yes, I realize this metaphor implies that what we do is sacrilege, but something must be said for the unholy effort it can take to free these beauts from the earth.

Figure 6: Lake Pelton Park campground.

Once you pull up to the rock shop at the entrance of RRR, you gotta go in and get registered for the draft. I mean for the digging. They will write your name on a card, and when you return from the beds, this card will allow them to process your goods to check out. Raw material is weighed and paid for by the pound, with a minimum of $12.50 total. Cutting is offered at $.35 and inch, and the rest of the shop and bulk stone is either by pound or by item. On their website, RRR specifies that they make no promises about getting your thunder eggs cut same-day, but when Alex and I asked what the wait was to have out seven halved, the answer was a meager "25 minutes or so." Checking in also comes with a schweet introduction to the methodology of thunder egg extraction, you get a map to the beds, and helpful advice from one of the owners [Figure 5]. Next, figure out which bed you want to hit first, head out the gate, and continue on down the road to find them. We went the Saturday of Labor Day weekend, and they had six beds available for digging, then. Apparently, they rotate some and keep some open all season. Incidentally, the season is usually April through October, but you can check it on the website at the end of this post. In addition to tips, the owners will also instruct you on the kind of digging required at each site. Difficulty can range from very easy (the things are tumbling out of the pit walls), to very hard (hard rock mining required). Given the title of this post, which difficulty would you guess we started with?

Figure 6: Moss Bed at Richardson's Rock Ranch.

Once we had the map and a plan (ha! plan...), I capered back to the car and Alex announced he would navigate us to the Moss Bed to find moss agates! Moss agates "contain seemingly organic tangles of hair-like growths," and can create all kinds of picturesque scenes and colors [Rocks & Minerals of Washington and Oregon, Dan R Lynch & Bob Lynch, 2012]. They are, in actuality, much sexier than this description, and the intrusions take on some really epic designs. These were agate chunks with intrusions of other mineral giving them crazy patterns and explosions of life-like color! What a find it was to check off my list.

Figure 7: Half of a moss agate thunder egg from Richardson's Rock Ranch.

When we got there, what we found was a smallish pit in the ground on a gentle ridge [Figure 6]. Setting down our two 5 gal. buckets abreast of the westward facing wall, I -inaccurately- declared that we needed to dig directly into the ground beneath our feet to reach the ripe layer of green ashen clay signalling the "goods ones, [we wanted] to find." I had been warned by the other owner that hard rock mining at the Moss Bed would take some work, but that if we put in the effort, the rewards would be great. Half an hour of pecking around below the wall took some of the excitement out of the spot I had rashly chosen, as we had bubcus to show for it. The thunder eggs were so tightly packed and formed together that it was nearly impossible to dig one out without smashing it and the ones around it. I presume this is the result of the pressure lightening so rapidly as the tuff cooled and rose closer to the surface, that the veins of gestating agate didn't have time to form discrete bubbles the way they did in other sites. Whatever the cause, this was not the kind of under-digging I had anticipated. But it's fine, because while Alex scored dozens of golf-ball sized ones while digging from the north face of the pit, I managed to work up a good cold bout of furious hacking & channel it into the bedrock.

There we were, the summer sun slowly creeping to a parallel above us, and I had provided none of the goods promised. My determination renewed after chiseling out increasingly larger chunks of green and broken geode linings, and I decided to take a different approach. Guided by the sagely advice from Theus Kester, self-proclaimed Wheel Master of the NW Rockhounds, I went back to the shelf where we started and rammed my chisel directly into the rock face where there was evidence of recent digging. Even if there was nothing obviously poking out at us from the rock when I started, I could see the bulbous edge of two or three thunder eggs rounding the scarred creases after removing some of the overlying material. Aroused by my call to arms, Alex quickly joined the effort and we finally hit a rich vein of blue agate woven with delicate orange tendrils [Figure 7]. After two hours of labor intensive hacking and a paucity of -totally epic- moss agate eggs, Alex and I saluted the family with the power tool & shade canopy (these real pros were a delight) and loaded up for the Red Bed. I think it is worth mentioning that, as we dug, four other small groups of people showed up, saw the effort and tools we were using in the Moss Bed, and abruptly turned their heels to go dig at easier sites.

Figure 8: Alex Jensen and I sitting at the Moss Bed face after extracting some sick moss agate thunder eggs.

Like I said you get out what you put in, and if you tuff it out at one of the hard rock mining beds at RRR you will walk away with your lust for thunder eggs sated. I've driven pretty far and endured some crazy terrain and temps just to go home without what I was looking for, but it's always an extra treat to share something good with someone good [Figure 8]. The next closest bed was the Red Bed, and that is where we went.

Side note: We pulled up & realized my geo hammer had been forgotten at the Moss Bed, and I drove back to find it. When I got there, I asked the man with the power tool if he had seen it, he quickly went to the bed of his truck to see if his family had picked it up. His wife pulled out two identical hammers, said they seemed to have an extra, and handed me one with a smile. I don't know whether the hammer I now possess is the very same one that my grandparents gave me over a decade ago, and it doesn't matter. The absolute equality of the gesture, so fluid and unassuming that we were the same, that our tools were the same, that our values and goals in being at RRR on a Saturday morning were the same, was a treat. Interactions like that pure and simple, forever ingratiate me to the greater rockhound experience.

Circling back, the Red Bed had metric tons of thunder eggs just laying about, and after cleaving a few from the soft, red-brown clay in the appropriate substrate, we headed to the fabled Blue Bed. If the posts on my handful of Facebook rock groups were to be trusted, the Blue Bed promised serious goodies. By that I mean a dependable supply of larger, dark blue agate geodes. This bed was a bit harder to extract than the Red, but nowhere near the difficulty of the Moss. That said, I found a nice little pretty, and hollered to Alex to extract its sibling from the same vein. We ended up with a matching pair of blue smiley thunder eggs, these faces revealed once they were cut [Figure 9]. We headed back to the shop, weighed our buckets, and selected a few choice finds to be cut. While Frank was explaining the different methods used to cut thunder eggs for people, he said the RRR was the first place to mainstream the process so that people could have their rocks cut quickly on site. This is kind of a big deal, because without a proper saw you might never see the treasures under the tuff exterior. Breaking thunder eggs with hammers is a clumsy way to go about things, and the fracture lines usually distract from any colors popping out at you. They did a good job of cutting ours, and all seven eggs were cut and ready faster than the estimated wait time! Needless to say, we were very satisfied costumers. I did pick up some rotary tumbler grit too, which was reasonably priced and whose Pro Polish came with a helpful warning, and moseyed on home.

Figure 9: Two Blue Bed thunder eggs from the same agate vein. Named Alex & Tori for their finders.

On our way out, one of the owners came out from behind the counter with a bag of my three grits and polish and asked me gravelly, "How much do you normally use for the final polish? Whatever it is, use about a fourth as much of this. It's powerful stuff, won't break down as quickly as the other polishes so be sure to use less." I told him I usually followed the two tablespoons per pound rule, and he chortled. "Yea, ok, then use like a teaspoon of this and you'll have better luck. Remember, with grits, the rule is usually 'Less is More'." Super helpful, super nice, super painfully hot outside. Hungry and tired, Alex and I swung into Madras for a late lunch of diner food, and returned to Astoria as victors of the thunder egg hunt! Overall, I have carried off more than a 20 lb. bucket of thunder eggs from RRR. The secret ingredient to a great rockhounding adventure is camaraderie, whether that be a coworker, rock shop owner, family on holiday, rock ranch operator, or just some down-to-earth thunder eggs. I propose that most of these will greet you with a smile [Figures 5, 8, & 9].

Richardson's Rock Ranch Website:

Happy Hounding!

*Relfie: rock selfie

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