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The septaria, a powerful stone of protection of the houses

Bérangère Maniglier

Posted on October 19 2021

What is the septaria stone?

A sedimentary rock

A stone that has formed over time, little by little.
Several theories exist, I will tell you the two most widespread.

A long time ago… at the time of the Cretaceous and the Paleogene , there are already a good hundred million years.

septaria, a sedimentary rock
During these times, the seas and oceans were at a much higher altitude than today. As a result, when the oceans retreated, the sediments were solidified and dried out by the ambient air. Several million years later, the oceans covered these solidified sediments. Each passage of the seas and oceans has led to a drying out of the always extreme concretions allowing the crystallization of many minerals in the sediments that have become rocky.

Another theory says that it is the skeletons of marine animals accumulated in the seabed, which are at its origin.

Over time, the water receded and the skeletons found themselves in the open air. With the help of the wind, clay came to surround these bones to form large clay heaps.

During the drying process, the clay cracked.
The place was free to let the calcite fit into the cracks.
And it is this famous calcite, whether yellow or white, which gives the magnificent lightning-shaped veins to the septaria.

Polished heart of septaria and yellow calciteFlashes of yellow calcite in the septariaHeart of septaria with yellow calcite

A mixture of clay

Septaria stone is a mixture of clay naturally containing a lot of siderite (iron carbonate) and calcite which forms the beautiful yellow or white veins.
yellow calcite veins
yellow calcite veins
Septaria stone is therefore a sedimentary rock called Marne, a mixture of limestone and clay (CaCO3) and yellow calcite. It belongs to the calcite group and its hardness is 4.
There are also inclusions of other minerals such as quartz, dolomite, barite, pyrite...

Several varieties of septaria stone

The septaria stone can present many colors on its surface: gray, beige, red, white, green, yellow or black. It is an organic mineral that has the ability to be variable, it can be completely opaque, but also particularly translucent.

The yellow septaria

Among the different varieties, the yellow septaria with beautiful veins of yellow calcite and a light brown to dark brown matrix. It comes mainly from Madagascar.
Pendant in septaria and yellow calcitePendant in septaria and yellow calciteseptaria pendant

Madagascar septaria

The wild Madagascar septaria has calcite, chalcedony, black velvet appearance, its shell has the 3 colors brown, gray, black... It is the most beautiful.

The septaria of Morocco

The black and white septaria which mainly comes from Morocco, is called "turtle stone", sometimes sold as a dinosaur bone...
Septaria called stone tortoise from Morocco
Septaria of Morocco

The Septaria of England

Pyrite septaria, found in England on the Wessex coast is beautiful and very rare. It is the fossilization of an ammonite with pyrite, the void of which has been filled with yellow or white calcite.

Septaria pyrites Septaria pyrites

I hope you have enjoyed this article and learned something from it... This stone which is often found under the name of septarian is really very special. What do you think ?

wild septariawild septaria wild septaria

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1 comment

  • Maniglier : September 27, 2022

    Super intéressant ! J’ai appris beaucoup de choses

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