Orpiment

Orpiment is a vivid yellow mineral, between lemon and gold in colour, made of arsenic and sulfur. It usually occurs as foliated or fibrous masses. Its name means “gold paint” in Latin: from ancient Egypt to medieval Europe, artists used it as a yellow pigment. But it is very toxic, so it is no longer used as a paint and needs care even when held as a specimen.

Yellow paint: Lumps of orpiment were found in an ancient Egyptian tomb of the 14th century BC. It was used on Central Asian wall paintings, on Chinese lacquer and on medieval European icons. Mixed with indigo dye it gives a deep green. Because it is poisonous and does not mix with lead- or copper-based paints, it was abandoned in the 19th century when cadmium and chromium yellows appeared. Hair remover: In rural India orpiment is mixed with slaked lime and used to remove hair. It has also been used in tanning to strip the hair from hides.

It has a hardness of 1.5–2 on the Mohs scale. It is soft enough to scratch with a fingernail. Its specific gravity is 3.48–3.49 g/cm³.

Its best-known localities: Twin Creeks mine, Potosi district, Nevada, USA; Quiruvilca, La Libertad, Peru; Shimen, Hunan, China; Baia Sprie, Maramureş, Romania; Zarshuran, Takab, West Azerbaijan, Iran.

Known localities in Türkiye: Çölemerik (Hakkâri city), Hakkâri, Türkiye; Balya, Balıkesir, Türkiye.

Its colour lies between vivid lemon-yellow and golden yellow; its streak (powder colour) is pale lemon-yellow. Realgar, which is almost always found with it, is orange-red. It is very soft (hardness 1.5–2) and can be scratched with a fingernail. Its perfect cleavage splits it into paper-thin sheets, and these sheets are flexible. Its lustre is resinous, and pearly on cleavage surfaces. The contents of powders sold in Türkiye as “hamam otu” (bath herb) are not guaranteed. In a Turkish study published in 2021, a sample bought from an herbalist turned out to be calcite and barium sulfate, with no arsenic detected; so the label tells you little about what is inside.

On the “street to diamond” value ladder it sits on step 4 of nine: Fine dimension stone and ore. Orpiment is sought as a collector’s specimen; its value depends on the vividness of its colour, the beauty of its crystals or sheets, size, freedom from damage and decay, and a famous source such as Quiruvilca (Peru), Shimen (China) or Twin Creeks (USA). Because it can break down into powder with light and humidity, well-preserved, bright specimens are scarcer. As a pigment, it gave way in the 19th century to safer yellows because of its toxicity and its incompatibility with other paints.

Its Latin name (auripigmentum, “gold paint”) reflects an old belief that orpiment contained gold, and Pliny (1st century CE) used the name. In China and Europe, alchemists searching for a way to make gold were drawn to orpiment by its bright yellow colour. In traditional Chinese medicine and in medieval Arabic pharmacy, orpiment was used as a medicine, that is, it was believed to help against some illnesses. Orpiment is arsenic sulfide; arsenic is a toxic element linked to cancer. That it was once used as a medicine does not show that it is safe or effective. Never put orpiment in drinking water (“gem water”), in the mouth or over heat, never breathe its dust, and never rub it on the skin as “hamam otu” or under any other name. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.

Orpiment contains arsenic. It is highly toxic if swallowed or if its dust is breathed in, and it can irritate the skin. Do not lick it, put it in your mouth or eat it; never put it in water to make “gem water” or an “elixir”; never use it as a medicine, cosmetic or hair remover. Do not heat it (arsenic fumes are released), crush it to powder or sand it. With light and humidity it can slowly turn into a white, crumbly powder (arsenic trioxide); do not touch specimens that have begun to decay with bare hands, and do not breathe the dust. Wash your hands after handling. Keep specimens away from children and pets, in a closed container in a dark, dry place. Orpiment pieces sold as ornaments (bookends, for example) have been recalled in the United Kingdom because they are toxic; do not keep such items in a child’s room or the kitchen.