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Septarian Properties Facts and Photos

round septarian nodule filled with yellow calcite crystals. On a black background

1. Septarian from Latin 'Septum'
2. Concretion or Nodule
3. Formation of Septarian Nodules
4. Moeraki Boulders
5. Healing Properties
6. Article Photos
7. Our Collection of Septarian

Septarian from the Latin 'Septum'

The word septarian comes comes from the Latin word septum meaning a dividing partition between two tissues or cavities.  In anatomy 'septum' is the cartilage in our nose that separates one nostril from the other.

Septarian nodules are distinctive, take on a high polish and are classified as a rock not a mineral.  Rocks are made up of different minerals whereas minerals are made up of crystals.

Septarian nodules are made up primarily of three minerals.  The yellow centre is calcite, the brown lines are aragonite or siderite and the outer rock is limestone.  They're sometimes likened to a prehistoric mud ball because of the way they formed.

Septarian Concretion or Nodule

Although often known simply as septarian, it's more accurate to refer to these geological structures as a septarian nodule or concretion.  Both are quite similar hence the terms tend to be used interchangeably.

In geology a nodule refers to a small irregularly shaped mass or lump of crystals or particles with a contrasting composition.  That basically means they're not all the same and may even be separated from the formation in which they occurred.

A concretion is a self contained cemented body of sediment.  The word also comes from Latin and means 'to grow together' or 'to harden'.

Despite being quite common concretions are considered to be geological curiosities.  This is because of the many unusual shapes, sizes and compositions in which they occur.

septarian nodule in the Natural History Museum London


How Septarian Nodules Form

Septarian is known to have formed during the Cretaceous Period.  This time period began approximately one hundred and forty five million years ago and ended sixty six million years ago around the time the dinosaurs disappeared.

These nodules (or concretions) formed in bodies of water as minerals and organic matter accumulated around a centre mass.  Gradually over millions of years and with the help of various geological processes, the mass hardened and became cemented together to form a nodule.

The minerals are likely to have included sandstone which is compacted grains of sand, shale which is compacted mud and siltstone and limestone which is primarily calcium carbonate.  The mineral aragonite is the crystalline form of calcium carbonate.  This chemical compound occurs naturally in rocks most notably as limestone.

Siltstone is fine grained silt, sand, clay or other materials carried in water before being deposited as sediment. 

Septarian nodules may well have formed in shallow lakes as the tide caused an accumulated mass to roll gently back and forth.  Over time with the addition of new layers of sticky mud the size of the mass increased.  During the hot summer months as the water receded the mud dried out. 

The newly formed structures then became buried under sediment.  Any cracks were slowly filled through seepage with a coarse crystalline substance such as silica (quartz) or calcite from the shells of dead marine creatures.

The crystals which later formed are the bright yellow centres of the septarian nodule.  A thin wall of calcite was also transformed into aragonite or siderite which separated the heavy clay exterior from the crystallized centre.

three polished septarian nodule spheres

Whilst the exterior of the septarian nodule was hard and featured a network of ridges, the interior contained distinctive angular cavities or cracks.  These became known as 'septaria' from the Latin 'septum'.

It's believed they were caused by the dehydration and shrinkage of clay.  Some geologists suggest it may be from the expansion of gases generated by decaying organic matter in the centre of the nodule.  They may also have been caused by fracturing or shrinkage caused by earthquakes or compaction.

Irrespective of how they formed, they subsequently filled with hardened natural minerals as groundwater changed and receded.  The minerals in the vast majority of cases were silica or calcite. 

Describing precisely how septarian nodules formed is not easy and there are many different views and interpretations.  Numerous questions remain unanswered and it's an ongoing topic of debate amongst geologists however the general formation process is one that's relatively common in sedimentary rocks.

Large Septarian Concretions | Moeraki Boulders

The moeraki boulders are large grey coloured septarian concretions.  They can be found on a stretch of coastline in New Zealand.

The boulders which were buried for millions of years beneath mudstone began to appear because of erosion from coastal cliffs.  In years to come more will emerge from the mudstone as geological changes continue to reshape the landscape.

It's believed the largest concretions took about four million years to get to their current size.

Almost identical spherical boulders can be found close to Hokianga Harbour on the North Island.  Similar concretions can be found in many countries around the world.

The Moeraki boulders are famous primarily because of their spherical shape and size.

Large spherical stone structures on the beach. Known as the Moeraki Boulders

Clickable image

Metaphysical Healing Properties

The properties of septarian encourage us to take care of the earth.  On a spiritual level it harmonises emotions with intellect, creates new ideas and the enthusiasm to follow them through.  It breaks repetitive routines or patterns of behaviour, extends patience and increases tolerance and endurance.

Septarian is a joyful stone that's emotionally nourishing and calming.  It can offer support for those who speak in public and can help improve communication within a small group.

This stone is used by healers because it's a tool for nurturing and showing care for others.  It has powerful healing abilities and is recommended for SAD (seasonal affective disorder). 

Article Photos

The septarian nodule at the top of our page is courtesy of Stan Celestian (Flickr).

The stone in the second photo is on display in London's Natural History Museum.  The septarian spheres are from our collection.  Both photos by Stone Mania ©.

All photos are clickable and redirect to the original non-compressed image.  The third photo redirects to an amazing photograph of the Moeraki Boulders on Koekohe Beach on the east coast of New Zealand's South Island.

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