“Golden Mystery Fossils in Posidonia Shale, Germany Solved: Pyrite Identified as the Source”

TEXAS – Mystery fossil glistening like gold found in the Early Jurassic site, Posidonia Shale, Germany, has been uncovered. As predicted earlier, this golden luster came from mineral pyrite (Pirit).

The mineral pyrite or iron pyrite, known as golden badar or pseudo-gold, is formed from iron sulfide with the chemical formula FeS₂. Pyrite is considered the most common mineral of the sulfide mineral group.

“It has long been believed that everything (in the Posidonia Shale) is pyritized,” Rowan Martindale, a professor in the Department of Geological Sciences at the University of Texas (UT) at Austin, told Live Science, Tuesday (9/5/2023).

Earlier this year, an international team of researchers visited an Early Jurassic site known for its exceptionally well-preserved marine animal fossils. They collected dozens of fossil samples of ammonites, bivalves and crustaceans the size of a palm or larger.

After the team looked at fossils around 183 million years old using a high-power electron microscope. They struggled to find pyrite in the fossils that emerged from the black shale. The research results were published in the March 2023 issue of the journal Earth-Science Review.

“There’s a bit of the mineral pyrite in some of the fossils, but basically it’s all phosphate calcite or yellow calcite. It was quite a shock for everyone,” he said.

After analyzing about 70 specimens, the shale surrounding the fossils is dotted with clusters of microscopic pyrite crystals, which are called framboids. It is a phosphate mineral with yellow calcite that is the source of the fossil’s golden glow.