Polished Septarian Pairs
Septarian nodules are concretions containing angular cavities or cracks called septaria. They are thought to form within layers of sedimentary strata before the rest of the sediment is hardened into rock. The concretionary cement often makes the concretion harder and more resistant to weathering processes than the surrounding strata. The septaria sometimes contain crystals precipitated from circulating groundwater solutions, most commonly of calcite.
The processes responsible for creating the septaria are not well understood. Proposed mechanisms include the shrinkage of the concretions' clay or organic rich cores due to dehydration, the expansion of gases produced by the decay of organic matter, and brittle fracturing of the concretion by earthquakes or compression.
Septarian nodules are sought after by rockhounds as collectable geological curiosities and as well as lapidary rough. When septarian nodules are sectioned, their exposed interiors sometimes reveal striking and aesthetic patterns.
| SeptarianPair2 - Polished Septarian Pair - $24.95 |
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Locality: Madagascar
Approximate Size: 65mm long x 42mm wide x 26mm thick. Please note the image above may be larger than life to help show the fine details.
Approximate Pair Weight: 94.3 grams
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