Glaucous

Glaucous is an adjective used to describe a pale bluish-gray or blue-green color, or a waxy, powdery coating on surfaces. The term derives from the Latin glaucus, from the Greek glaukos, meaning "bluish-green" or "gleaming gray."

In botany, glaucous refers to leaves, stems, or fruits with a frosted, waxy coating that gives a pale blue-green or gray appearance. This bloom can often be rubbed off to reveal a greener or different color beneath. The coating helps reduce water loss and reflect excess sunlight, aiding drought tolerance in some species. The bluish bloom is common on many plants and is often valued in horticulture for its ornamental texture. The characteristic bloom can also appear on grape skins and on the surfaces of certain plums and peaches.

In zoology and ornithology, glaucous describes pale blue-gray coloration in plumage or on surfaces such as shells. Birds known for glaucous plumage include the glaucous gull and the glaucous-winged gull, named for their pale blue-gray appearance. Some mollusk shells and other animal surfaces exhibit a glaucous, waxy look as well.

In geology and mineralogy, glaucous is used to denote a dull blue-green or gray glaze on minerals and rocks, often giving a matte, waxy or powdery appearance. The term is used broadly across disciplines to indicate this characteristic color or surface finish.