What's the noun for pearliest? Here's the word you're looking for.
pearl
A shelly concretion, usually rounded, and having a brilliant luster, with varying tints, found in the mantle, or between the mantle and shell, of certain bivalve mollusks, especially in the pearl oysters and river mussels, and sometimes in certain univalves. It is usually due to a secretion of shelly substance around some irritating foreign particle. Its substance is the same as nacre, or mother-of-pearl. Round lustrous pearls are used in jewellery.
“It gives noticeable glow without the pearlescence I know many of you hate, and garners more compliments than almost any foundation I've worn.”
“The natural pigments in Rooibos combined with mother-of-pearl selected for its extreme finesse and purity create a secret alchemy of luminosity and pearlescence.”
“Arctic char, slow-baked to a pinkish-orange pearlescence, is also well treated with a sprinkling of wild mushrooms and firm edamame in a yeasty, off-dry sake sauce.”