Rather Than Amber

By Meilan Solly
smithsonian.com
January 24, 2019

Until now, Gizmodo’s Ryan F. Mandelbaum reports, most scientists believed that such high-quality fossil specimens were unique to amber. But an intriguing find by gemologist Brian Berger could upend this notion, proving that the slow-forming gemstone opal is also capable of preserving the remains of ancient animals.

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It's believed that perhaps 30 million years ago, lots of silica was released into a solution which filled cracks in the rocks, layers in clay, and even some fossils. Some of them became precious opals. It takes about 5 to 6 million years to make a 1 cm opal to mature. source

5 to 6 million years! Imagine an insect laying under/over ground undisturbed for long enough time for silica to include it, or rather cover it. More likely there was a more rapid process involved where this insect was buried quickly and left undisturbed for a shorter period of time allowing silica to encase it. Undisturbed because there was nothing left alive to disturb it.