Septarian Nodules: were formed during the Cretaceous period, 50 to 70 million years ago. Decomposing sea life killed by volcanic eruptions, had a chemical attraction for the sediment around them, forming mud balls. as the ocean receded, the balls were left to dry and crack. Because of their bentonite content they also shrank at the same time trapping the cracks inside. As decomposed calcite from the shells was carried down into the cracks in the mud balls, calcite crystals formed. A thin wall of calcite was transformed into aragonite separating the bentonite heavy clay exteriors from the calcite centers. Because of this, the nodules are called Septarians.
The name Septarian is derived from the Latin name, Septem, meaning seven. This relates to the fact that the mud balls cracked with 7 points in every direction, thereby creating the beautiful design.
Septarians are composed of Calcite (The Yellow Centers), Aragonite (The Brown Lines) and the Outer Grey Rock is Limestone. Occasionally the fossil or some of the fossils which started the formation of the rock is noticeable in the rock.
You are buying this lot of Septarians photographed, that have been cut in half and polished. You end up with a nearly mirror image, (minus the material lost during the cutting process) You will receive this group of 8.
You are buying something that has been millions of years in the making, please do not look for perfection, look however at Mother Nature's creation perfection. All these are individual and their origin is Morocco.
You can see the ruler in the photo to give you size idea. Use these Septarians to add some million year history to your mosaics, or if you are a fossil freak you will probably add them to your collection.