The word "melaconise" is not commonly used, and there are several possible spellings for it. One possible way to spell it is /mɛləkənaɪz/ , where the stress is on the second syllable. The word may mean "to make dark or black", or may be a variant of the medical term "melanocyte", which refers to a type of skin cell that produces pigment. As with many obscure words, the spelling and pronunciation of "melaconise" may vary depending on the source and context.
An impure black oxide of copper, occurring in veins in powdery masses, arising probably from the decomposition of other ores.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.