orpiment pigment, yellow pigment, زرنیخ زرد, اٍرپیمنت

Ingredients

orpiment stone, arsenic, sulfur

Evidence

"The results of Raman spectroscopy showed that Arabic gum and sesame oil did not interfere significantly with the pigment spectrum, making orpiment identification possible using this method. PLM also greatly assists in identifying orpiment based on its crystallographic features. SEM-EDX examinations also showed arsenic and sulfur content of 29.09% and 49.82% (wt%) in this pigment."

Remarks

The orpiment samples from Tekab (Zarshouran) were identified as arsenic sulfide (As2S3). SEM-EDX analysis (Table 3, p. 25) showed 49.82 wt% Arsenic and 29.09 wt% Sulfur. PLM analysis (Table 2, p. 24) revealed crystals with irregular angular shapes, high relief, blade-like structures, and strong birefringence with yellow, pink, and light green to blue interference colors under crossed polars (XPL). Raman spectral bands were identified at 100, 133, 150, 177, 198, 289, 307, 353, and 379 cm-1 (p. 26). The band at 353 cm-1 is noted as a strong characteristic of arsenate vibrations in the sample (p. 26).