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Septarian Nodules by Undistilled Septarian Nodules by Undistilled
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Title: Septarian Nodules
Medium: Digital Photography
Photographer: Aaron J. Greenblatt
Camera Type: Panasonic DMC-LZ7 Lumix 7.2 MP
Editing: Edited in PhotoShop 7.0 for color accuracy, size, and to apply copyright and border.

Location: Photograph taken at the 2008 Southeastern Michigan Gem and Mineral Show at the Southgate Civic Center in Southgate, Michigan. Show hosted by the Midwest Mineralogical & Lapidary Society.

Description: One large display case at the show held nothing but very large pieces and slices of septarian nodules. The above septarian nodule slice was more than 10 inches in width and contained a filled-in core of calcite crystals. Unfortunately, there was no location information in the display case stating where it was discovered.

This piece when originally found was spherical in shape and that's typical for these types of specimens. It was then cut into slices and each slice was polished to show the beautiful calcite interior as well as the internal portions of the randomly fractured/re-healed cement shell. The cement started off as mud probably at the bottom of a sea. Over millions of years and under pressure, the mud gradually dehydrated and chemically changed into a much harder, more durable natural cement.

I'm of the opinion that septarian nodules are one of the most beautiful types of concretions and that they make for some of the most interesting specimens. To me they appear to look like an internal calcite explosion that has been frozen in time.

How Did They Form? Although it has been commonly assumed that these concretions grew incrementally from the inside outwards, a further study of these formations indicates that this is not the case. The fact that radially orientated cracks taper towards the margins of septarian concretions is taken as evidence that the outer shell of the nodule was stiffer during formation while the inside was softer. This is presumably due to a gradient in the amount of cement precipitated - more on the outside, less on the inside.

Basically, once the outside solidified, no more cementing could take place on the inside and thus the inside where the calcite crystals grew formed last. This is in keeping with how many other types of geodes and agates are believed to be formed. However, the actual process that created the septaria, which characterize septarian concretions, remains a mystery.

Information Source: [link] (wiki - Septarian Concretions)

Legal: Copyright © Aaron J. Greenblatt. All rights reserved. Commercial use prohibited. This image and commentary may not be used for any reason without expressed written consent.

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Add a Comment:
spartout Featured By Owner Dec 31, 2009
All of these crystals make me whana visit canada and greenland:)
Undistilled Featured By Owner Dec 31, 2009
I really like Canada. There's a very nice fossil bed not far over the Canadian border from where I live. I've visited it a number of times and found some really nice coral, crinoid, and trilobite specimens.

There's also a plethora of petoskey stones that wash up on Canadian lake shores and they don't mind if you collect and keep them.

spartout Featured By Owner Jan 1, 2010
Nice my dad is thinking about going on a fishing trip this year in greenland (the worlds geologigly oldest country) and at the same time i whould posibly go crystal hunting. If not i am bound to go to east Iceland this year raindeer hunting.
Undistilled Featured By Owner Jan 1, 2010
Either of those sound like great adventures.

spartout Featured By Owner Jan 3, 2010
I know i just came back from my sumerhouse and he and i wenth duck hunting and as usual he never hits any duck but was lucky to hit one. I also took my camera and took lots of photos.
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Submitted on
December 30, 2009
Image Size
887 KB


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