sulfides
Orpiment
As2S3
- Also known as
- auripigmentKing’s yellow
- Crystal system
- monoclinic
- Hardness
- 1.5–2 on the Mohs scale
- Lustre
- resinous
- Colour
- Lemon to golden yellow
- Where it forms
- With realgar in low-temperature veins and hot spring deposits.
- Chiefly from
- Hunan, ChinaPeruNevada, United StatesTurkey
Why it is that colour
The arsenic sulfide compound. Its golden colour is the origin of its name, from Latin auripigmentum, gold pigment, and of the alchemical hope that it contained gold.
Safety
Arsenic trisulfide, soft, flaky and toxic. Do not handle it more than necessary, do not powder it, and wash your hands afterwards. It should never be put in water or in the mouth, and the flakes should not be inhaled.
Where it comes from
Chinese and Peruvian specimens. No longer mined commercially.
Historical use
King’s yellow was orpiment, and it was used in illuminated manuscripts and in painting until it was replaced by safer chrome and cadmium yellows in the nineteenth century. It cannot be used next to lead or copper pigments, because the sulfur reacts and blackens them, which restricted how painters could use it.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Prominent in alchemy, where its golden colour and its association with sulfur made it a candidate for transmutation. Used as a pigment and a depilatory in the classical and medieval world, and in traditional medicine, with the predictable consequences.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Worth knowing
Orpiment and realgar sit together in the same deposits, one yellow and one red, both arsenic sulfides, and to an alchemist that pairing was extremely suggestive. Sulfur and arsenic were both principles of transformation; a golden mineral that was not gold looked like gold in an unfinished state.
Arsenic's presence in that tradition is one reason alchemy was dangerous work. Between the mercury, the arsenic, the antimony and the lead, a working alchemical laboratory was a catalogue of the most toxic elements available, handled by people with no concept of chronic exposure.
Identity checked against IMA-CNMNC master list, June 2025.