Marcasite The mineral marcasite, sometimes called white iron pyrite, is iron sulfide (FeS2) with orthorhombic crystal structure. On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. It typically forms under low-temperature highly acidic conditions.
Rhodium is a noble metal with a whitish gray appearance, and it is typically applied to metal through electroplating. A plating of rhodium is applied over either sterling silver or alloys to give a piece of jewelry a bright, glossy and long-lasting finish.