Such sulfuric acid aerosols are already responsible for the bulk of nacreous clouds that form in the polar stratosphere; added particles would just amp up the natural process (although it might also amp up damage the ozone layer). (scientificamerican.com)
The mantle of the animal coats the irritant with many layers of nacreous material to reduce irritation, until the pearl is formed. (AmbergrisCaye.com)
They are called nacreous clouds and noc - tilucent clouds. (hubpages.com)