Back in the Shale

On my bucket list was driving the curvy back-roads over the Northwest Passage in Idaho. As I was loading up thundereggs in Madrid, Oregon and wondering how best to get back home, I thought that driving on Hwy 13 in 2013 sounded like a dangerous but worthwhile adventure. And guess what? I ended up in Montana. Well... I had to go east to get home, so I ended up in Glendive with two days to hunt the Pierre Shale for septarians. It had been several years since I was here, and I figured there may be a nodule freshly exposed. At the very least, a wade of the large gravel bar under the Black Bridge of the Yellowstone River and finding some pretty agate was a certainty... not. When I got to the city park and walked to the river, I saw it was up and muddy... no agate would be found. It would have to be a septarian or bust.

I woke up early in this noisy city park and headed south to Cedar Creek. I had the advantage of knowing the exposures that had produced on my previous hunts, so I headed to the most likely spot. This spot was a high shale bluff on a drainage of Cedar Creek. When it really rains in this area, this drainage would become a river, and much erosion would occur. This is just what I needed to expose a fresh nodule. As I drove my four wheeler over the numerous roads created by the oil and gas folks, I noticed how many more wells there were from the last time I was out here. Lots of holes dug on this anticline. I parked the ATV and hiked the half mile up the drainage to the shale bluff. What luck, as I spotted a large nodule showing halfway up the bluff and in the prime location of the shale for a barite septarian!

Click to Enlarge

I thought if I dug the shale all along the same plane, I could find another... and this thought became true.

As much shale as I could dig came off of that bluff but the two shown in the previous picture were all I found. The biggest nodule was dug out first and the weight was a very bad sign. I could barely lift it off the ground. At least 120 lbs. If it had a hollow, it would be very small. The smaller one was dug, and it too was very heavy... darn. These had no chance of having large enough cavities for the nice barite crystals to have room to grow. Should I try to get these to my ATV whole? Should I try to open them now and see if they were worth keeping? The deer flies were making it impossible to think, so I called it a day and rolled the two nodules up high on the opposite bank and hid them with cedar branches.

Before I closed my eyes that night I knew what I would do. I would rent a dolly from the local hardware store, and use it to get the whole nodules down the half-mile to the road. But Murphy's law took effect overnight and it rained, turning the shale to glue and the creek drainage to quicksand. It took all day to complete my plan. The heavy round nodules were not staying on the dolly, and I ran out of duct tape and busted all my bungee cords. Still, I knew I could not do a good job of opening them with thousands of deer flies buzzing my head and waiting for an opportunity to strike. Also, once these nodules were opened, they needed to be treated with care and not rolled in the dirt or bounced around on the ATV. It was five o'clock when I finally got the two nodules strapped to my four wheeler. It felt really good, and I didn't even care what was in them. I had accomplished my goal and I was pooped.

After getting the two nodules home, I carefully opened them with a chisel. I decided against cutting them as the only one I did cut, from a previous trip, didn't turn out well. The saw cut through a beautiful ammonite and butchered the barite. The first picture shows the biggest nodule, and it did have barite. The cracks were so small though, the barite crystals shared both walls and split into.

Notice the seashells in the center. I think when/if this nodule were to be broken further, a nice calcite coated ammonite might show up. Ill keep this nodule safely in its own plastic tub until that day comes. This septarian turned out better than I thought when I first lifted it. It has pretty golden calcite and distinct seashells (small ammonites and pelecypods) defining the nucleus. Around the edge of the nodule is the acicular barite clusters, and even though they are split, the bourbon tipped crystal sprays are still pretty.

The smaller nodule popped open like it knew how best to display its center. I barley touched the hammer to the chisel when a beautiful ammonite appeared, to show off its well preserved mother of pearl shell. There was just a trace of barite in the small cracks, but this rock did not need it. A truly wonderful septarian from the Pierre shale of eastern Montana.