Lot 105B
Sumatra, Indonesia, Jurassic geological period, ca. 201 to 144,000,000 BP. An extremely rare concretion that looks amazingly like a fossilized peanut - which was the identification given to prior owner. The mode of siderite concretions, also known as "Septarian" concretions, is still debated. But here's the prevailing hypothesis: Siderite (FeCO3) often grows in the buried sediments like a tumor does in your body. When carbonate-rich (C03) water moves through sediments buried just below the seafloor, it sometimes encounters a nucleus, such as decomposing leaves, animal carcasses, feces, or other organic matter. The bacteria that are munching on the decomposing organic matter cause the carbonate to react with iron (Fe) that is dissolved in seawater, and the two join together to form a siderite envelope around the organic matter. This process continues, layer-by-layer, as long as there is available carbonate and iron-bearing fluids to supply the growth of the concretion. Sometimes this process is thought to occur so fast in soft muddy sediments that it traps fluids in the concretion, and doesn't allow the muds to 'dry out' before the concretion envelops the muds. The net result is that thousands to millions of years later, these fluids eventually work their way out of the concretion, or evaporate in situ (the water leaves as vapor), and the concretion cracks from the outside inward. By this time, there is no more available iron to bind with the carbonate that is dissolved in the water, so calcium assumes the role of binder-of-carbonate, and the mineral calcite often forms in the interstices of the cracks, much like amethyst lines geodes. The cracks tend to have crisscrossed patterns, much like mud cracks in a puddle do. Custom stand. Measures an amazing 6-3/4"H.Provenance: Ex-private Boulder, CO collection. All items legal to buy/sell under U.S. Statute covering cultural patrimony Code 2600, CHAPTER 14, and are guaranteed to be as described or your money back. A Certificate of Authenticity will accompany all winning bids. #108481
- Condition: Intact with small loss to very top, else near choice.
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| From: | To: | Increments: |
|---|---|---|
| $0 | $299 | $25 |
| $300 | $999 | $50 |
| $1,000 | $1,999 | $100 |
| $2,000 | $4,999 | $250 |
| $5,000 | $9,999 | $500 |
| $10,000 | $19,999 | $1,000 |
| $20,000 | $49,999 | $2,000 |
| $50,000 | $99,999 | $5,000 |
| $100,000 | $199,999 | $10,000 |
| $200,000 + | $25,000 |