Septarian nodules, also known as dragon stones, are highly sought after by rock hounds and mineral collectors because they formed millions of years ago in a unique way. These dark mud balls are distinctive stones with yellow, gray, and brown tones in large art-like bands. The grays and browns come from dead algae while the yellow crystals are made of calcite.
When talking about this mineral you’ll notice collectors interchange the word nodule and concretion. I believe the word concretion is the better word to describe a septarian nodule but I’ll leave it up to you to determine what you prefer to say. Keep reading below to find out the difference and what makes these rocks so cool.
What Is A Septarian Nodule?
Septarian nodules are a type of concretion. Mudstone combines with calcite or another carbonate-rich mineral, and the calcite follows the pattern of radiating cracks that grow during the stone’s formation.
In every case, septarian nodules are comprised of at least two minerals. The matrix of these nodules is often grey. At the same time, the interior varies from white to brown with tinges of orange throughout.
Septarian stones have a cracked egg-shaped appearance within their host rocks which gives the nodule a unique appearance when you dig it out of the ground. After the septarian nodule or concretion has been removed from the dirt, a lapidary artist will have a couple of choices to make when polishing it. They can cut the stone in half and polish the flat surfaces or polish the outside of the nodule only.
Are Septarian Nodules Rare?
Septarian nodules aren’t necessarily rare and are reasonably accessible. Smaller samples are more abundant; larger specimens are rarer when they’re cut as slabs or giant eggs.
Free-form shapes or spheres with partial openings displaying the crystals within fetch over $100. Larger specimens can be valued at well over $1,000. While some samples can be costly, it isn’t out of reach. Moderate slabs, nodules, and spheres can be found for less than $50, with smaller specimens even more affordable.
Regarding septarian jewelry, it can be just as affordable as standalone specimens. Septarian necklaces or rings can be found at about $50, but when some lux metals are added, the piece will fetch a higher price.
Where Can You Find Septarian Nodules?
Septarian nodules can be found in a few areas. Much of the material commonly seen comes from the mineral-rich island of Madagascar. The specimens from this region are typically filled with Calcite and a thin layer of Aragonite – the darker layer between the orange-to-yellow center and an exterior matrix of shale or mudstone.
Many septarian nodules come from Muddy Creek in the state of Utah. I’ve heard that some of the nodules found around Muddy Creek are filled with everything from the typical yellow calcite to stunning amethyst.
Septarian nodules are also found (in lesser amounts) along the Gulf of Mexico and Michigan. Around Michigan, these nodules are often called “Lightning Stones.”
Make sure you bring the right rockhounding tools if you decide to visit the dig site.
How To Polish Septarian Nodules
This all depends on the nodule you’re working with. Some people prefer to saw them in half before they start the polishing process. In contrast, others like to polish the exterior of the nodule.
- If you saw the nodule in half, you’ll need an 8-diamond saw machine. Or take it to a lapidary and see if they’ll cut it for you.
- After halving the nodule, you’ll have two pieces to work on the cabbing machine.
- Start with a 260-grit diamond wheel to remove the saw marks left on the flat surface.
- Next, you’ll move up to the 600-grit wheel, which will bring a dull shine to the surface of the nodule.
- Once the deep scratches are removed with the 600-grit, move up to a 1,200-grit wheel.
- You’ll notice the face of the nodule getting closer to a fine polish, but it’s not quite there.
- Next up is the 3,000-grit wheel.
- The final step is to polish the entire surface of the nodule with a 14,000-grit wheel.
A Diamond Pacific Titan Cabbing Machine or something similar is perfect for the job. The process will be the same if you choose to go with a flat lap. However, the way the stone is handled would be different.
A concretion is a mass of mineral matter embedded within rock layers, including shale, limestone, and sandstone. They take shape when minerals settling out of water collect around a nucleus, like a leaf, pebble, bone, shell, or fossil.
Concretions are generally harder than the rocks surrounding them. Over time, concretions can weather out when the softer rock surrounding it erodes. While concretions are often rounded, they can be long, lumpy, oval, irregular, or disk-shaped. Color, hardness, and size vary, from smaller than a pin’s head to several hundred pounds.
Septarian concretions occur in the Cretaceous shales of the Smoky Hilly region. The networks of crisscrossing ridges on the exterior of a septarian concretion can give the stone a turtle shell appearance.
In contrast to most volcanic geodes, septarian geodes are a form of sedimentary geode. They formed on the sea beds millions of years ago. When they dried out, they cracked, and the interior hollows. The interior of these geodes usually became partly or entirely filled with other minerals that give Septarian unusual features and texture.
They’re unique and beautiful works of art created by nature.
Septarian geodes have a higher value than some stones. Prices vary depending on the size, type of minerals, and type of crystals. You might find smaller septarian geodes for $20 to $90, with larger and more intricate specimens ranging from $100 to $500. The larger, more profound pieces will only level up the price range.