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.
Brown A brown coating gives a piece of jewelry the color of chocolate (dark) or coffee (light) brown. This color of plating is not commonly seen in jewelry, and presents unique and exclusive statement pieces.