The orpiment is a Minéral Jaune composed of sorting Sulfure of Arsenic of formula As₂S₃. its name comes from the Latin auri pigmentum , to indicate the color of mineral close to that of the Or.

Poison, orpiment was used since the Antiquité by the Greek , the Romains and the Égyptiens like Pigment. The beautiful gold yellow color of orpiment had drawn the attention of Old. It was known of Aristote and Pline which called it “auri pigmentum”. The alchemists roasted the Sulfure S to prepare white arsenic or Arsenious oxide, and it seems that elementary arsenic was isolated as of XIIIe century, but that remains dubious until the XVIIIe century.

With the Moyen-âge one manufactured it while melting of the Réalgar and the Soufre.

Unsuitable with painting on walls or panels, because blackening in contact with the air because of the Sulfur, it was used little apart from the miniatures in the Manuscrit S where it replaced sometimes gold.

It usually was crushed then mingled with water and a binder proteinic like egg or the adhesive with parchment. Many Irish manuscripts of the first millenium owe him a share of their magnificence, among which the Livre of Kells , the Livre of Durrow or the Évangéliaire de Lindisfarne .

It is used today industrially as pigment, but also for the production of semiconductors and photoconductors, like in the fireworks.

crystalline System monoclinical, group of space P 2₁/ N