Septarian Nodule

What septarian Nodule actually is

The species behind septarian Nodule is carbonate concretion whose internal shrinkage cracks have been filled with yellow calcite and brown aragonite - a concretion, not a single mineral, Calcite CaCO3 (yellow), aragonite CaCO3 (brown), in a grey-brown limestone or mudstone host, sometimes with barite; it forms in the aggregate system.

Iron and organic staining for the brown septa; the yellow is calcite with trace iron is responsible for the colour — and the chromophore, not the name, is what decides whether a colour is stable.

On the instruments it reads a refractive index of 1.486-1.658 and a specific gravity of about 2.50-2.90, with rhombohedral calcite cleavage in the fill cleavage.

Where septarian Nodule comes from

Commercial material comes from Orderville and Kane County, Utah, USA, Mahajanga Province, Madagascar - the main source of polished spheres and eggs, Morocco and Tunisia and Dorset, England (Kimmeridge and Oxford Clay concretions).

Different localities give different colour and different clarity, and the trade prices them differently. We state which one.

How septarian Nodule is treated

Cut, polished and very commonly resin-stabilised, since the cracks make it fragile; some Madagascan pieces are dyed to brighten the yellow. Soft, acid-sensitive and unsuitable for rings. 'Dragon stone' is a marketing name. Not CITES; Madagascar has intermittently restricted mineral export.

We state the treatment on every stone, including when the honest answer is that it cannot be determined. A treatment disclosed is a fact; a treatment discovered later is a refund.

What septarian Nodule is confused with

Watch for Ordinary calcite geodes, Dyed and resin-filled composites and Petrified wood — these are what turn up sold under this name.

The separation is rarely a matter of opinion: refractive index 1.486-1.658 and specific gravity 2.50-2.90 settle most of it in a minute, and magnification settles the rest.

What septarian Nodule is used for

The trades that buy septarian Nodule are mineral collecting, decorative objects, architecture and interiors and jewellery. They do not want the same thing, and they do not pay in the same unit.

We quote each application in the unit that trade actually buys in, by the specimen, by the piece or by the square metre.

Durability and care

Hardness 3-4; cleavage rhombohedral calcite cleavage in the fill. That combination decides what it can safely be set into.

Below about 5.5 a stone will be scratched by ordinary household dust, which is largely quartz. That does not make it unusable — it makes it a pendant, an earring or an object rather than a ring worn every day.

Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.

What septarian Nodule costs

Expect roughly $10-80 for small polished eggs and spheres; large display pieces $100-1,500, depending on quality.

That is a range, not a quote. Colour, size, clarity, cut and origin move the figure a long way inside it, and the only honest price is one given against a specific stone. Send us what you need and we will price it.

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