Septarian is a unique and visually striking sedimentary rock, prized by rock hounds and collectors for its distinctive patterns and colors. Composed of minerals like calcite, aragonite and barite, septarian forms when cracks develop in the rock as it dries and contracts after formation. These cracks then fill with minerals, creating the maze-like patterns the rock is known for. With its brown and gray tones mixed with vibrant yellow, white or clear calcite veins, septarian has a one-of-a-kind appearance. But with several lookalike rocks, how can you reliably identify septarian?
There are a few key ways to distinguish real septarian from rocks with a similar look. First, examine the rock for septarian’s characteristic web-like cracks filled with calcite or other minerals. The patterns these cracks form are totally unique to septarian. Next, check the color—septarian’s mix of grays and browns with vibrant calcite veining is distinctive. Also look at the shape—septarian’s irregular, rounded forms are different from the ovals of thundereggs. Finally, test the weight and hardness, as septarian is relatively heavy and soft compared to lookalikes.
While the look may be mimicked, septarian’s distinctive patterns, colors, weight and hardness set it apart from other rocks. By knowing what makes septarian unique, rock hounds can reliably identify this treasured stone. Whether for collecting or decorative use, properly identifying septarian is key to appreciating the one-of-a-kind beauty of this sedimentary rock.
What is Septarian Stone?
Septarian stone, also known as “Dragon stone” or “Dragon egg stone”, belongs to a class of sedimentary rocks known as concretions. Concretions are hardened mineral deposits that form within softer sedimentary rocks like mudstone. As the mudstone erodes, the tougher concretion nodules are left behind.
Septarian concretions form as nodules or irregular blobs ranging from a few inches to several feet across. They are composed primarily of calcite and aragonite, two carbonate-rich minerals that make up limestone. However, they also frequently contain barite, fossils, and other minerals that provide their distinctive colors and patterns.
The name “septarian” comes from the Latin word “saeptum” meaning partition or enclosure. This refers to the rock’s crisscrossing cracks or septa that divide the nodule into sections. These cracks occur as the concretion shrinks during formation, and later fill with additional minerals like calcite. When cut and polished, these cracks produce the varied patterns septarian is prized for.
The maze-like cracks within septarian nodules result in patterns unlike any other rock. When identifying septarian, the first thing to look for is these distinctive crack formations that resemble a river system or spiderweb spread across the rock.
The cracks form as the nodule shrinks and contracts during the process of concretion formation. As the outer shell hardens, it pulls away from the center, creating radial stress cracks extending out from the middle. These cracks then fill in with mineral deposits over time, creating the signature septa or partitions.
When cut and polished, the array of interconnected cracks filled with vivid calcite, aragonite or other minerals forms the one-of-a-kind patterns characteristic of septarian. The contrast of dark host rock crisscrossed by the light-colored infilling creates eye-catching designs treasured by rock collectors.
No other rock develops these extensive crack formations filled in with such vibrant mineral deposits. So the presence of septarian’s radial arrays of mineral-filled cracks is a key identifying trait.
In addition to its distinctive patterning, septarian can be identified by its unique color combinations. The host concretion is typically brown, gray, yellowish or reddish due to the mineral composition of the original mudstone. Contrasting vibrantly with the mute concretion colors are the bright white, yellow or clear infillings of the cracks.
The various minerals that compose septarian result in a diverse mix of tones:
- Brownish-gray – The dark mudstone concretion is colored by trace amounts of iron and organic material. Shades range from light beige to almost black.
- Yellow – Yellow calcite is by far the most common infilling deposit of the cracks. Its vibrant color offsets the dark host rock.
- White – White calcite or barite also frequently fills the cracks, producing eyecatching light streaks criss-crossing the rock.
- Clear – Nearly invisible when wet, clear calcite deposits in crack seams give a glassy luster when polished.
- Reddish – Hematite staining can tint some septarian nodules red or orange. Iron oxide replaces the limestone to create the vivid coloring.
- Greenish – Serpentine minerals like antigorite may impart an olive green hue in some specimens.
No other rock combines such a diverse mix of muted earth tones and brightly colored calcite veining. This distinctive combo of colors helps set septarian apart from lookalikes.
Weight and Density
Due to its high concentration of dense, metallic mineral deposits, septarian has an unusually high specific gravity for sedimentary rocks. The multitude of calcite, barite, pyrite and other mineral infillings gives septarian a density of 2.6 to 2.9, heavier than typical sedimentary rocks.
The weight of septarian can aid in distinguishing it from rocks that otherwise look similar. When handled, septarian feels substantially heavier than imposter rocks of comparable size. If you pick up a rock that appears to be septarian but feels light for its size, it is likely an imitator rather than real septarian. Likewise, a small rock with seemingly excessive heft for its size is a good septarian candidate.
In addition to its weight, septarian’s hardness can also help identify it. The Mohs scale ranks minerals on a scale of 1 to 10 based on hardness, with diamonds being the hardest at 10. Septarian has a hardness of around 3.5, relatively soft due to its limestone and calcite composition. This is on par with other sedimentary rocks.
A simple way to test hardness is by trying to scratch the rock with a steel nail. If the rock scratches, it falls at about a 2.5 on Mohs scale. Septarian’s softness means a steel nail can leave a clear scratch in the rock. Agates, jaspers and other mistaken identities will be much harder, resisting scratching. So while not definitive on its own, hardness can be another useful identifying factor.
Septarian nodules frequently contain fossils, which aid in identifying the rock. The fossils are marine creatures that were deposited along with the original sediment that formed the mudstone surrounding the septarian. They become encapsulated within the concretion as it grows.
Common fossils found inside septarian include:
- Ammonites – coiled shell fossils that resemble the modern Nautilus
- Belemnites – ancient squid fossils that left bullet-shaped internal shells
- Crinoids – segmented fossils from ancient relatives of sea stars
- Shark teeth
- Fish bones and scales
Finding any fossils within a septarian-like rock is a strong indication it may be genuine. While not all septarian contains fossils, their occasional presence can help confirm identification.
Septarian nodules have a characteristic shape that helps distinguish them. Unlike many other concretions found in sedimentary formations, septarian tends to form in highly irregular, asymmetric shapes. Smooth rounded lobes, elongated ovals, flattened pancake shapes and bizarre amorphous nodules are all common.
In contrast, other concretion types like thunder eggs typically have a more consistent round or oval shape. The irregular, random shapes of septarian blobs are an identifying trait that sets them apart from concretions with more standard forms.
Septarian’s exact mineral makeup also aids in properly identifying the rock. The principal minerals are:
- Calcite – Makes up the majority of the concretion. Also the most common mineral deposit in the cracks.
- Aragonite – A less stable, higher energy polymorph of calcite also abundant in the rock.
- Barite – Barium sulfate mineral that infills cracks in some septarian. Adds weight.
- Hematite – Iron oxide mineral that gives some nodules a reddish hue.
- Pyrite – Metallic mineral that oxidizes upon exposure to air, causing oxidation stains.
- Gypsum – Hydrated calcium sulfate found as crystal coatings in some specimens.
- Celestine – Strontium mineral additive that can impart a blue coloration.
- Limonite – Iron hydroxide that leaves a yellow-brown stain in some nodules.
This combination of minerals gives septarian a density and coloration unlike other sedimentary rocks. Understanding its definitive mineral profile can thus help positively identify septarian.
Differentiating From Lookalikes
While septarian has a distinct look, there are some rocks that may appear similar at first glance. However, upon closer inspection these rocks lack some of septarian’s unique identifying traits. Being able to differentiate septarian from common lookalikes is key for accurate identification.
Thundereggs are concretions like septarian that form within sedimentary basins. However, there are a few key differences:
- Shape – Thundereggs are oval or spherical, unlike septarian’s irregular blobs.
- Patterns – Thundereggs lack septarian’s distinctive radial cracks filled with vivid mineral deposits.
- Composition – The mineral makeup is more homogeneous, often just agate or jasper rather than calcite.
- Source – Thundereggs most often originate in volcanic ash beds rather than marine mudstone.
So while thundereggs share a concretion origin, their appearance is quite distinct from septarian’s patterns, colors and shapes.
Tiffany stone is an uncommon sedimentary rock with eye-catching purple, white and brown banding. But there are several traits that set it apart from septarian:
- Mineral content – Tiffany stone contains fluorite, opal and chalcedony rather than calcite or aragonite.
- Patterns – Tiffany stone has multi-colored bands rather than septarian’s fracture patterns.
- Source – Tiffany stone comes from a single mine in Utah, unlike the diverse areas septarian is found.
- Hardness – Tiffany stone is harder at 4 – 5.5 on Mohs scale.
So while sharing some visual similarities, Tiffany stone’s composition and source localities don’t match up with septarian.
Agate and jasper are microcrystalline quartz minerals that are sometimes mistaken for septarian. However, though they may imitate septarian’s colors, agate and jasper are minerals rather than rocks. They also lack septarian’s distinctive patterns, fossils, and high density. So agates and jaspers can be readily distinguished from true septarian.
Other Sedimentary Rocks
There are many other sedimentary rocks such as limestone, sandstone, or shale that may vaguely resemble septarian. However, detailed inspection reveals major differences:
- Patterns – These rocks lack septarian’s characteristic radial fractures filled with vivid mineral deposits.
- Fossils – You won’t find the typical marine fossils of septarian.
- Composition – Other sedimentary rocks have a more homogeneous mineral makeup.
- Texture – Sandstones and shales have layered, granular textures absent in septarian.
So while they may seem superficially similar, other sedimentary rocks are easy to differentiate once you know septarian’s distinctive traits.
Comparison Table of Septarian and Similar-looking Rocks
|Feature||Septarian||Thunderegg||Tiffany Stone||Agate/Jasper||Other Sedimentary Rocks|
|Composition||Calcite, aragonite, barite||Agate, jasper, chalcedony||Opal, fluorite, chalcedony||Microcrystalline quartz||Variable (limestone, shale, etc.)|
|Colors||Gray, brown, yellow, white||White, gray, brown, red||Purple, white, brown||Various colors||Variable|
|Patterns||Distinctive radial cracks||Banding, none||Banding||Banding, breccia||Layers, none|
|Hardness||3.5 Mohs||~7 Mohs||4 – 5.5 Mohs||6.5 – 7 Mohs||Variable|
|Shape||Irregular nodules||Oval, round||Irregular nodules||Irregular nodules||Variable|
|Formation||Concretions in mudstone||Concretions, replacements||Veins/fissure fillings||Secondary mineral infilling||Various|
|Source Localities||Western US, N. Africa, Australia||US, Mexico, Europe||Utah, US||Worldwide||Worldwide|
When in Doubt, Ask an Expert
For rockhounds new to collecting septarian, it can understandably be difficult at first to confidently identify specimens. If you obtain a rock that resembles septarian but you have any doubts, consulting an expert can provide confirmation.
Geologists who specialize in mineralogy and sedimentary petrology are most qualified to authenticate septarian. Many universities have geology departments that may offer free identification. Museums of natural history are another good option. There are also private rock shops that provide identification services for a small fee.
Having a reputable specialist positively identify your specimen provides certainty and documentation. This is especially important for septarian intended for collection or decorative use where authenticity adds value. No amount of research on distinguishing traits beats an expert’s evaluation.
The Geologic Origins of Septarian
In order to fully understand septarian stone, it helps to learn how this unique rock formed millions of years ago. Septarian’s journey begins with the deposition of marine sediments, followed by complex mineralization processes to produce the finished rock we know today. Understanding septarian’s geologic origins reveals what gives this stone its one-of-a-kind beauty.
Deposition of Marine Sediments
Septarian begins life as carbonate-rich marine muds accumulating on the floors of shallow seas between 50 to 400 million years ago. Composed of clay, silt, organic debris and calcite mud, these sediments accumulated up to several hundred feet thick in some areas. Marine creatures lived and died in these seas, leaving behind fossilized shells and bones in the mucky sediments.
As layer upon layer of slightly different muds built up, the sheer weight compressed the lower sediments into rock, lithifying them into mudstone and shale. These embryonic sedimentary rocks contained the components that would later transform into septarian.
Within the muddy marine sediment layers, some zones began to solidify faster than surrounding areas as mineralization commenced. This created irregular lumps and blobs of denser, more cemented mudstone that grew into concretions.
While the exact mechanism is debated, likely factors accelerating local consolidation include:
- Changes in sediment composition
- Higher organic content
- Zones of lower permeability
- Differences in water chemistry
These concretions formed uneven blobs ranging from less than an inch up to several feet across. The developing septarian nodules encapsulated any marine fossils within, preserving them intact.
Cracking and Infilling
As the nodules hardened further, they began to shrink — a process known as syneresis. This caused the outer concretion shell to pull away from the center, creating radial cracks extending through the concretion. As some areas shrank more than others, intersecting cracks formed, dividing the nodule into septa.
After cracking formed the septarian pattern, mineral-laden waters flowed through the cracks depositing calcite, aragonite, barite and other minerals. This infilling produced the vivid white, yellow or clear veins starkly contrasting with the dark host rock.
Different successive mineralization episodes created concentric crack rings as the nodules continued to shrink. Each new generation of cracks crossed-cut older filled cracks, resulting in complex, intricate patterns.
Erosion and Exposure
Finally, over millions more years, continuous erosion wore away the softer surrounding mudstone, gradually revealing the concretions. Colluvial processes broke apart and weathered the exposed septarian nodules. Tumbling in streams rounded their shapes.
By this long, incremental sequence of geologic processes, the finished septarian stones prized today were created. The minerals, cracks and marine fossils locked inside reveal the entirety of septarian’s formation history stretching back 50 million years or more.
Mining Locations and Sources
Due to its uneven, sporadic distribution, there are only a limited number of areas worldwide where septarian is mined or collected as nodules weather from sedimentary outcrops. Understanding where septarian originally formed helps provide clues to a specimen’s possible source. Here are some of the major occurences of septarian:
The Western U.S. is one of the most significant sources of septarian in North America. Important collecting sites include:
- Utah – The central region around Salt Lake City offers abundant nodule collecting from clay beds near Red Fleet Reservoir and elsewhere. Distinctive yellow calcite crystals fill cracks in many Utah septarian samples.
- Wyoming – Concretions weathering out of the Trout Peak Formation near Douglas are a prime source. Some rare giant nodules over 6 feet across have been found here.
- Oregon – Septarian concretions originating in volcanic mudflows called lahars are found in counties like Grant and Baker.
- Nevada – Areas around Elko and Eureka contain abundant septarian, sometimes with gorgeous clear to white calcite seams.
- New Mexico – Septarian nodules have been collected in the Jemez Springs region north of Albuquerque.
- Texas – Scattered finds have been made near Amarillo and other Panhandle locations.
In addition to the Western states, marine septarian has been found in Indiana, Tennessee, Kansas, Oklahoma and Iowa. So a wide span of U.S. geologic formations has produced collectible septarian.
Northern Mexico has a number of notable septarian sources:
- Nuevo León
The arid desert climate of these Mexican states helps erode mudstone beds to expose the concretions. Dark gray-brown limestone with vibrant yellow calcite infillings characterizes most Mexican septarian.
The island nation of Madagascar off the coast of Southeast Africa provides abundant septarian to the gem and mineral market. Most Madagascar material is recovered from the Mahajanga region and is derived from Jurassic-Cretaceous marine sediments.
Madagascar septarian tends to have darker gray-black host rock with smaller white calcite seam fillings. Fossils like ammonites are also common. Much Madagascar septarian has been tumbled or cut into egg-shaped spheres.
Morocco and Algeria in Northern Africa produce septarian, where it is sometimes called “Atlas Stone.” Concretions weather out of Paleozoic and Cretaceous mudstones in the Atlas Mountains. More iron-rich than Madagascar material, Moroccan septarian has vivid yellow and red staining.
Septarian nodules have been found in a number of sedimentary basins across Australia. Notable collecting regions include:
- Carnarvon Basin along the central Western coast
- Murray Basin in South Australia
- Eromanga Basin inland Queensland
Australian septarian tends to be smaller on average than American or African material, though giant examples up to 750 lbs. have been found.
Scattered pockets of septarian occur across Europe, although not as abundant as in other continents.
- England – Septarian concretions have been found weathering from Cretaceous sediments in counties like Dorset, Yorkshire, Somerset and Kent. These are geologically related to sources across the English Channel in France.
- France – The Paris Basin has produced attractive septarian nodules. Iron oxide mineralization gives some French septarian a reddish hue.
- Romania – Small gray-brown calcite vein septarian originating from Jurassic marine beds are collected sporadically in areas like Transylvania.
- Poland – Concretions found in the Holy Cross Mountains derived from Cretaceous sediments.
- Sardinia – Occasional pocket finds of septarian have been made on this Mediterranean island.
So while not producing huge volumes, various locales across Europe offer limited septarian hunting for diligent collectors.
On New Zealand’s South Island, the Moeraki Boulders along the coast north of Dunedin are a famous septarian location. These large spherical concretions ranging up to 6 feet across crack as they erode from Paleocene mudstones, displaying halos of calcite cracks.
Canada has scattered septarian occurrences where ancient marine shales are exposed.
- Alberta – Nodules found weathering from the Cardium Formation in the foothills of the Rocky Mountains.
- Manitoba – Septarian concretions recovered from Cretaceous sediments near Flin Flon.
- Nova Scotia – Concretions originating from Carboniferous shales.
In Russia, septarian concretions have been found in Jurassic sediments from the Volga River region. Additional occurrences likely exist in the extensive shale deposits across Russia, but collecting access is limited.
Cutting, Polishing and Preparing Septarian
One of the allures of septarian is seeing the gorgeous designs revealed when the nodules are cut open and polished. Properly preparing surfaces unleashes the vibrant colors and patterns. While beginners can tackle simple slicing and polishing, mastering the cutting of septarian into fine decorative objects requires expert lapidary skills.
Cutting Rough Stones
The first step in preparing septarian for display or sale is to cut open the nodules, exposing the interior filled cracks and intricate designs. There are several approaches:
- Cut in half – Simply slicing a small to medium septarian stone in two reveals the centre. A slab saw with a diamond blade is beginner friendly for this.
- Quartering – Cutting a nodule into quarters creates attractive slices showing the radiating septa. Band saws allow quartering larger stones.
- Complex sections – More elaborate sectioning like hinged cuts display the most patterns. This advanced technique requires expert rock cutting skills.
- Thin sections – For jewelry use, thin slices under 0.25 inches showing fine details are ideal. A slab saw equipped with a diamond blade thicknesser attachment can produce these.
- Tumbling small stones – Smaller nodules under 2 inches can be tumbled whole, leaving a natural shape with polished septarian designs.
The goals of cutting are maximizing the visibility of interior details while retaining strength and durability in the resulting materials.
Shaping and Polishing
Once cut, the septarian surfaces require polishing to achieve a clean, smooth finish that brings out vivid colors and patterns:
- Grinding – Silicon carbide wet grinders in progressively finer grits remove saw marks and shape edges. Starts with ~100 grit.
- Sanding – Using wet sandpaper up to 2,000 grit or higher polishes away fine scratches, readying for final polish.
- Polishing compounds – Applied to felt or leather wheels, compounds like cerium oxide give final high polish, enhancing chatoyance.
- Vibratory – Loads small pieces in ceramic media with polishing compound to finish polish all sides. Quick but lower luster than wet methods.
- Tumbling – Rotating drums with abrasives polish small pieces, leaving rounded natural shapes.
Well-polished septarian displays dramatically sharp contrast between the host rock matrix and brightly colored calcite veins. Reflective polish accentuates chatoyance and iridescence.
Cutting Decorative Forms
Cutting septarian into decorative objects like spheres, obelisks, eggs or jewelry requires master lapidary skills guided by the natural fracture patterns. The lapidarist must visualize how cracks will intersect complex forms. Tricky sections maximize both stability and aesthetic designs. High-end lapidary work can transform septarian into art.
Septarian’s cracks mean it requires stabilization to prevent breakage when cutting thin sections or fragile shapes. Vacuum impregnation with epoxy resin fills internal voids, strengthening the stone. Crack filling and sealers can also stabilize flawed areas. Stabilized material holds up to cutting impossible on raw septarian.
Setting Septarian in Jewelry
With its striking patterns in a palette of earthy tones contrasting with bright calcite veining, polished septarian presents unlimited possibilities for jewelry. From statement necklaces to bold cuff links, septarian provides an organic, one-of-a-kind aesthetic perfect for handcrafted jewelry designs.
Cabochons cut from septarian nodule sections make ideal focal points for rings, pendants, bracelets and more. The domed, polished ovals and freeform shapes display the beauty of septarian’s intricate cracks and fossil patterns. Simple bezel or prong settings allow maximum visibility.
Thin, flattened slices sawed perpendicular to the septa planes create septarian geode images when set in jewelry. Rings, earrings, brooches and bolo ties can frame these mini geode slices to striking effect.
Small whole septarian nodules polished into natural shapes work well for necklaces and earrings seeking an organic feel. The natural contours create interest while different sides showcase the diverse patterning.
Carved pendants, charms and other objects cut from septarian, like skulls or animal forms, provide a carved gemstone look. The veining patterns add detail within carved shapes.
Septarian’s colors and shapes lend well to mosaic inlay patterns for cuff links, decorative boxes, knife handles and more. Alternating geometrics with turquoise, coral and other stones create Navajo-style designs.
Large polished freeforms in the 100 carat range produce substantial statement necklaces, especially when accented with gold or silver details. The huge pieces become wearable art.
Caring for and Storing Septarian
While septarian’s patterns and colors may last millions of years in nature, collectors should take basic steps to preserve and protect specimens once acquired. Simple practices to care for, handle and store your septarian properly will maintain its condition and value.
When placing septarian stones on display:
- Avoid direct sunlight which can fade colors over time.
- Use soft supports that won’t scratch polished surfaces.
- Seal any open cracks that could accumulate dirt.
- Keep away from extreme heat sources that may dry/dehydrate specimens.
When handling or examining septarian:
- Avoid knocking or dropping stones which may chip or crack.
- Never scrape or gouge specimens.
- Wash hands thoroughly before handling to avoid oils and dirt.
- Handle with care to not scratch polished finishes.
To safely clean dirty septarian:
- Use a soft brush and mild soap to gently wash stones. Avoid acid or alkaline cleaners.
- Ultrasonic cleaners work well to loosen debris from cracks.
- Rinse thoroughly and pat dry with soft cloth after washing.
- After cleaning, re-apply mineral oil to polished surfaces.
For safe long-term storage:
- Wrap larger specimens with foam or paper to prevent rubbing.
- Place smaller pieces in collector cases with padded compartments.
- Keep valuable museum-grade pieces in archival mineral storage boxes.
- Store in a consistent cool, dry, dark environment to preserve colors.
To prevent damage to your septarian:
- Never expose to freezing temperatures which may crack specimens along flaws.
- Keep away from harsh chemicals and solvents that may react with minerals.
- Prevent moist storage conditions that can degrade the rock over time.
- Don’t let pieces bang together which can chip and scratch.
By following these simple practices, your prized septarian specimens will retain their stellar beauty for many years to come.
The Allure and Collectibility of Septarian
What drives the strong attraction septarian holds for collectors and rockhounds? The vivid designs, organic look and traces of primordial Earth make septarian an appealing, sought-after rock. Its unique properties also make museum-grade specimens highly valued.
The complex, maze-like web of mineral-filled cracks traversing septarian creates mesmerizing designs. The intricate networks draw the eye as it traces the meandering paths of contrasting colors. The patterns exhibit the fractal-like, repetitive complexity of nature that humans intrinsically find beautiful.
Appeal of the Earthly
With its earthen tones and natural shapes, septarian presents raw beauty unspoiled by human hands. Its organic irregularity contrasts with the geometric uniformity of our artificial environments. Septarian’s earthy authenticity speaks to our inner affinity for the elegance of nature.
Window to the Past
Traces of ancient marine life preserved as fossils in septarian provide a tangible connection to primordial worlds. We gaze through a window to Earth’s distant past when these creatures swam the seas. This evokes our innate curiosity about life’s history on the planet we call home.
Mystique of Transformation
Septarian’s mineralization journey that transpired over eons inspires wonder at Nature’s patient transformative powers. Ordinary sediments metamorphosed into such patterned elegance fuels the mystique septarian carries. We are drawn to things that carry the imprint of great change over time.
Rarity of Material
With limited geographic sources, septarian’s irregular distribution adds to its collectibility. Fine museum-grade pieces with gorgeous designs or rare patterns have escalating value. The difficulty in finding pristine specimens generates scarcity that feeds demand.
In different ways, septarian’s patterns, organic origins, fossil content, geologic history and scarcity factor all contribute to its widespread allure for collectors. Nature gifted septarian an improbable beauty that sparks fascination in those who experience this exceptional sedimentary treasure.
Septarian’s distinctive aesthetic makes it one of the most prized and coveted sedimentary rocks. But with several imposter lookalikes, accurately identifying septarian is an essential skill for collectors. By learning to recognize septarian’s unique patterns, colors, fossils, weight, hardness and composition, rockhounds can reliably distinguish this stone from similar rocks. When paired with an expert opinion, this knowledge helps ensure your specimen is true septarian stone.