Patina

PATINA (probably from the Latin word for a flat dish, from patere, to lie open; cf. “paten”), a thin coating or incrustation which forms on the surface of bronze after exposure to the air or burial in the ground. It is looked on as a great addition to the beauty of the bronze, especially when it is of the green colour found on antique bronzes. By extension, the word is applied to the discoloured or incrusted surface of marble, flint, &c., acquired after long burial in the ground or exposure to the air, and also to the special colour given to wood surfaces by time.

PATINA (/pəˈtiːnə/ or /ˈpætɪnə/) is a thin layer that variously forms on the surface of copper, brass, bronze and similar metals and metal alloys (tarnish produced by oxidation or other chemical processes) or certain stones[1] and wooden furniture (sheen produced by age, wear, and polishing), or any similar acquired change of a surface through age and exposure.

See also:
Patina, Verdigris – Outdoor Lights
External links:
Patina – Encyclopædia Britannica
Patina – Wikipedia