A pearl cocoon? As in, "a pupal casing made by moth caterpillars and other insect larvae." (Thank you Wikipedia!) Yes, a gold and pearl cocoon, as in an insect cocoon, is exactly what I am talking about!
This is the work of a caddisfly larvae. These young caddisfly build a cocoon in lakes, rivers and streams. They product silk and together with rocks and twigs, they build a cocoon. The silk acts like a glue holding their little cocoon together. They then enter a pupa stage for a few weeks or month. As water temperatures cool, they emerge and swim to the surface where they fly off into adult life. As adults, caddis flies resemble moths.
Anyway, after years of observing these caddisfly larvae, French naturalist and artist, Hubert Duprat, wondered if the caddis flies would use any materials to build their cocoon. He introduced flakes of gold, pearls and opals to the caddis flies and they did intact use them for their cocoons. Again they use their own silk as the glue to hold their pupal constructions together. And together with the caddisfly, Hubert creates wonderful world of art...a gold and pearl cocoon!