Composition of the heating-induced metallic-looking coating

Determine the exact composition and formation mechanism of the thin metallic-looking surface coating produced on some coarse CM-simulant particles during radiative heating.

Background

Heating experiments using coarse CM simulant particles produced a thin coating with metallic optical properties that was absent before heating. Crushing the particles showed that the material formed a surface film rather than a metallic interior. The paper considers chemical reactions or limited melting of a metal-bearing mineral as possible explanations, but the coating’s composition and origin remain unresolved.