EONS: 100 SLICED POLISHED MADAGASCAR AMMONITES, 1-3 cm

EONS: 100 SLICED POLISHED MADAGASCAR AMMONITES, 1 cm ~ 2.9 cm

DESCRIPTION: This auction is for a sealed bag of 100 pairs (200 total pieces) of sliced and polished ammonites similar to the pairs shown at bottom. They are in the highest jewelry grade, alternately called A, or AA, or AAA, or #1 grade, and are sized 1 cm ~ 2.9 cm (.4 inches ~ 1.1 inches) measured at their widest dimension. If you need larger quantities please drop me an email.

The specimens were chipped out of the entombing rock, the tough fossilized barnacles removed, and only then was the outside laboriously buffed by hand. After that, it was sliced in half and polished by hand to a glossy finish. This gives us an inside look at the individual growth chambers and the story behind them: as the animal grew, it would extend the open end of the shell by adding a larger growth chamber, pull its body forward into the new chamber, and then seal the old one -- but not before evacuating the water from its old chamber. Thus, each time the shell got bigger by one chamber, the newly sealed chamber maintained neutral buoyancy. Unlike a fish, the ammonite had neither lateral fins nor an air bladder, so it needed the air-filled chambers to keep it from sinking to the bottom.

Eventually though, when the animal died, it did sink to the bottom where it was covered by sediment which became rock after eons of high pressure and heat which occur miles below the Earth’s surface. During that process, the individual chambers experienced different fates. The chambers that ruptured relatively immediately became filled with gray organic-rich sediment, which are time capsules of the ocean bottom at that time. Microscopic analysis shows tiny fossilized fish bone fragments, shell parts, coprolites, and other remains of life. But the chambers that did not rupture followed a different path. For millions of years these remained empty, but eventually calcium-rich ground water leached into the chambers and deposited its calcite within them. The most impermeable of these remained hollow and exhibit a crystal-lined surface. Those that were less resistant experienced a heavier water flow and were completely filled with water born crystalline deposits. The different colors occur as a result of the different chemical composition of the water at the time that the crystals were forming. For example, the local groundwater may have been calcite-rich 90 million years ago because the formation was close to a river that was carrying the material from newly formed mountains. Then perhaps 40 million years later plate tectonics had carried the formation further south where ground water contained different trace elements due to another set of geological circumstances. And so any chambers that were still hollow at this time, were impregnated with different groundwater that caused different colors and crystalline structures. This was a constant process and so this specimen carries evidence of its entire 110-million-year plate tectonic ride. This specimen will appeal to not only fossil collectors, but also to home or office decorators, appreciators of the very old, fans of the unusual, nautical aficionados, aquarium enthusiasts, science buffs, educators, and parents who want to encourage scientific interest within their children.

Genus: Cleoniceras
Age: Cretaceous (approx. 110 million years ago)
Found: Majunga, Madagascar (the huge island off the southeast coast of Africa)

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30 DAY RETURN POLICY: If you decide within 30 days of auction end that you do not want an item purchased from me for ANY REASON, then you can return it in as-sold condition for a refund of the closing bid price.

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