This is the “Fossil Friday” post #93.  Expect this to be a somewhat regular feature of the website.  We will post any fossil pictures you send in to esconi.info@gmail.com.  Please include a short description or story.  Check the #FossilFriday Twitter hash tag for contributions from around the world!

---

For this week, we have a tale of both beauty and of woe.  It comes to us from long time ESCONI member Marie Angkuw.  Her photos of ammonite fossils show the beauty that can be found in fossils.  Unfortunately, there is a sad end to her tale… pyrite disease.  Hopefully, you’ll never experience it, but it’s more common than you think.  Thanks for the contribution, Marie!

Pyritized ammonite fossils from the Jurassic Coast, England by Marie Angkuw

Most people are familiar with the classic ammonite shape. Their graceful, coiled forms can be seen in jewelry, home décor, and even logos on wine bottles. Ammonites are cephalopods that lived during the Jurassic and Cretaceous Periods, becoming extinct about 66 MYA. Their closest living relative is the Nautilus. Though fossil ammonites can be found throughout the world, of special interest to me are the ones found in Lyme Regis, England, aka the Jurassic Coast. An ESCONI member for over 13 years, I and several other club members have collectively scoured the beaches of Lyme Regis and neighboring Charmouth 17 times!

Unfortunately, many of the beautiful pyritized ammonites that I collected have succumbed to Pyrite Disease, even after the recommended thorough washing and drying of the specimens. Pyrite Disease is a chemical reaction that is initiated by the fossil’s exposure to moisture and air. The resulting iron sulfide (rust), corrosive sulfuric acid, and sulfur dioxide gas cause the specimens to disintegrate. Many paleontological collections have been affected by Pyrite Disease, and curators continue to explore remedies to prevent the loss/damage to valuable collections. I have been advised to store my fossils with silica packages or even coat the specimens with resin, but for all practical purposes, the decay cannot be arrested. Worse, it can spread from one specimen to another.

This Eoderoceras sp. fossil was found on Charmouth beach in 2018.

Though the specimen is essentially destroyed, I can appreciate that the chemical process which created the fossil has been replaced with another that will essentially leave the ammonite a powdered outline of its original beauty—as transitory in its fossilized form as it was when it swam the oceans 200 million years ago.