melanization
/ˌmɛlənʌɪˈzeɪʃn/(also melanisation)
noun
1 Biology. The production, accumulation, or deposition of melanin; the development of a brown or black colour as a result of this.
2 Soil Sci. The darkening of a topsoil by the incorporation of humus.
Origin
1920s; earliest use found in Quarterly Review of Biology. From melano- + -ization. Compare melanized, and later melanize.