AN IRIDESCENT AMMONITE
AN IRIDESCENT AMMONITE

SOUTH DAKOTA, USA

Details
AN IRIDESCENT AMMONITE
SOUTH DAKOTA, USA
From the upper Cretaceous, Fox Hills Formation, (circa 65 million years ago) the specimen of Sphenodiscus splendens showing opal like iridescence of red, green, turquoise and purple to both sides, supported on an acrylic stand.
9in. (23cm.) diameter

Lot Essay

The shimmering, metallic colours were caused by the combination of millions of years of compression and the mineralization of iron, copper and silica which precipitated from volcanic ash. The opalescent layers of colour are particularly prized in the Chinese philosophical system of Feng-Shui.
The ammonites are a group of animals that lived in the seas from the mid-Devonian (approximately 400 million years ago) to the end of the Cretaceous. The sequence of events that famously killed off the dinosaurs also drove the ammonites to extinction.

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