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Septarium Nodule Slices

Great South Gems and Minerals - Septarium Nodule Slices
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Septarian nodules or concretions are formed from a sedimentary process. Concretions form within laayers of sedimentary strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest fo the sediment is hardened into rock. There is an important distinction to draw between concretions and nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body.

Descriptions dating from the 18th century attest to the fact that septarian concretions have long been regarded as geological curiosities. Because of the variety of unusual shapes, sizes and compositions, concretions have been interpreted to be dinosaur eggs, animal and plant fossils, called pseudofossils, extraterrestrial debris, and even human artifacts.

Here in the United States we have many variations of the septarian nodules or concretions such as Septarian concretions, Cannonball concretions, Hiatus concretions, Elongate concretions, Moqui Marbles and, Kansas pop rocks, all of which are basically the same thing and were formed in the same way. The "cementing" substance of these unusual formations varies from one type to another. They may be calcite, iron oxide, or other minerals.

Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth (Mozley, 1996; Raiswell and Fisher, 2000). In concentric growth, the concretion grows as successive layers of mineral accrete to its surface. This process results in the radius of the concretion growing with time. In case of pervasive growth, cementation of the host sediments, by infilling of its pore space by precipitated minerals, occurs simultaneously throughout the volume of the area, which in time becomes a concretion.

Septarian nodules, or concretions, vary in shape, hardness and size, ranging from objects that require a magnifying lens to be clearly visible to huge bodies three meters in diameter and weighing several thousand pounds. The giant, red concretions occurring in Theodore Roosevelt National Park, in North Dakota, are almost 10 feet in diameter.
Item Number: M499
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Great South Gems and Minerals - M499 - Septarium Nodule Slices
$14.00 each

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