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TWO IRIDESCENT AMMONITES

CANADA

Details
TWO IRIDESCENT AMMONITES
CANADA
From the Upper Cretaceous, Bearpaw formation (75-72 million years ago), the exceptional 15-inch specimen of Placenticeras intercalare displaying a dazzling iridescence of reds and oranges, greens and rich blues. The 9-inch specimen with localised rainbow iridescence amongst dark reds.
15 x 13 x 1.1.2in. (38 x 33 x 3.5cm.)
9 ¹/₄ x 7 ¹/₂ x.1/2in. (23.5 x 19.5 x 2cm.)
Provenance
Acquired from Canadian trade in 2016.

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James-Hyslop
James Hyslop Head of Department, Science & Natural History
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Lot Essay

The opal like iridescence of these ammonites from Alberta, Canada has been termed 'ammolite', and since 1981 has had the status of a gemstone. 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 molluscs that lived in the seas from the mid-Devonian (approximately 400 million years ago) to the end of the Cretaceous (65 million years ago). The sequence of events that famously killed off the dinosaurs also drove the ammonites to extinction.