A clear to white liquid secreted by sea hares (genus Aplysia) that becomes viscous upon contact with water

“The attack on a sea hare by a spiny lobster causes release of the whitish opaline, followed the co-release of both opaline and ink.”

Any of several minerals resembling opal, including a variety of yellow chalcedony

Opal glass

Resembling opal in its iridescence; having a milky white iridescence.