Caddisfly larvae

Caddisfly larvae protect themselves by constructing elaborate armors from gravel, sand, twigs, and other debris, which they “glue” together using excreted silk. The tiny moth-like insects scavenge whatever material is suitable from their environments, including anything you choose to give them. French artist Hubert Dupratwas among the first to take advantage of the insects’ predilections by supplying them with gold flakes, opal, turquoise, rubies, and pearls. The resulting cases are intricate works of art that can be strung up like beads to create one-of-a-kind jewelry.

http://www.ecouterre.com/artists-enlist-caddisfly-larvae-to-build-jewelry-from-precious-metals/