A History of Hindu Chemistry from the Earliest Times to the Middle of the Sixteenth Century A.D. v1.c13.19

v1.c13.19

Iron pyrites [Fe S₂] is brass-yellow in colour, and its dimorphous form marcasite is pale bronze-yellow; but there are other pyrite-like minerals which are silvery white; for instance, cobaltite (Co S₂. Co. As₂), smaltite (Co As₂), löllingite (Fe As₂ with S) and leucopyrite (Fe₃ As₄). Iron pyrites roasted in air would give a red residue of Fe₂ O₃. But it seems more likely that the "golden-yellow" variety is copper-pyrite, which has a deep yellow colour and besides which iron-pyrite when freshly fractured would appear almost silvery in colour. In that case the "essence of the appearance of copper" might be the metal itself.¹