the.com/nacre
A mollusk's interior decorating that humans mistook for treasure.
means The iridescent inner shell layer, also called mother-of-pearl, that mollusks build from calcium carbonate and protein.
from From Arabic naqqarah by way of medieval Latin and French, eventually surfacing in English as the polished name for shell shimmer.
Light trickColor comes from layered crystals, not pigment.
Pearl makerSame stuff coats irritants into pearls.
Tougher thanFar stronger than the chalk it's made of.