At first, they looked like muddy chunks of ancient shell. But these 20-million-year-old fossil oysters had been slowly replaced with agate over time, creating hidden patterns inside the stone. When ...
The brilliant iridescent hues found in ammolite come from tiny air gaps in the fossils’ layers, a new study finds. By Alexa Robles-Gil Millions of years ago, squid-like creatures called ammonites swam ...
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