User:Arccc/Orpiment

Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with the formula. It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of another arsenic sulfide mineral, realgar. Orpiment takes its name from the Latin auripigmentum (aurum, "gold" + pigmentum, "pigment") because of its deep-yellow color. Orpiment is widely used in ancient artistic creations, medical, and other fields. Orpiment is toxic and hard to conserve, and is no longer commonly used in contemporary time.

Etymology
Orpiment takes its name from the Latin auripigmentum (aurum, "gold" + pigmentum, "pigment") because of its deep-yellow color.

The Greek for orpiment used by Theophrastus in the fourth century B.C. was arsenikon, deriving from the Greek word arsenikos, meaning "male", from the belief that metals were of different sexes.

The Chinese term for orpiment is Ci-Huang (in Pinying), meaning "female yellow".

The Persian for orpiment is zarnikh, which is based on zar, the Persian for gold.

The Latin term auripigmentum or auripigmento (literally, gold paint) used by Pliny in the first century referred to the color and also to the fact that it was supposed to contain gold.

Visual characteristics
Orpiment is a type of lemon-yellow to golden or brownish-yellow crystal commonly in foliated columnar or fibrous aggregates, may alternatively be reniform or botryoidal, granular or powdery, and rarely as prismatic crystals. As a pigment, orpiment is usually described as a lemon or canary yellow or sometimes as a golden or brownish yellow.

In the Munsell color system, orpiment is designated brilliant yellow, Munsell notation 4.4Y 8.7 /8.9.

Orpiment and realgar
Orpiment and realgar are closely related minerals and are often categorized in the same group. They are both arsenic sulfides and members of the monoclinic crystal system. They form in the same geological environments and can be closely associated with the same deposits. They have similar physical properties and similar histories of use by man.

In Chinese, names for orpiment and realgar are Ci-Huang and Xiong-Huang, respectively meaning "female yellow" and "male yellow". Their names symbolize their affinity and regular occurrence in close natural conjunction.

Orpiment and realgar can be distinguished by their different visual characteristics. While orpiment was distinguished by its brilliant golden-yellow color, realgar, in contrast, normally has an orange or reddish hue.

Permanence and conservation
Yellow orpiment (As2S3) degrades into arsenic oxides. Because of its solubility in water, arsenic oxides readily migrate and are found throughout the multi-layered paint system. The widespread arsenic migration has consequences for the conservation of orpiment as a pigment in artistic creations.

For instance, orpiment painted out in glue medium has partly altered to white arsenic trioxide after exposure to light for fifty years at the Fogg Museum of Art, Harvard University. Orpiment used to coat manuscript paper in Nepal to repel insects often turns white in time.

Because of this widespread potential for damage, preventing the degradation of arsenic pigments like orpiment should be prioritized and conservators should minimize exposure of objects containing arsenic pigments to strong light, large fluctuations in relative humidity, and water-based cleaning agents.

Artistic uses
Orpiment has a history of widely being used as a pigment in artistic creations around the world. It was one of the few clear, bright-yellow pigments available to artists until the 19th century.

Regions using orpiment in artistic creations
In ancient Egypt, lumps of orpiment pigment were found in a fourteenth-century tomb. Even though there are no references to orpiment as a pigment in China, orpiment were is known to have been used to color Chinese lacquer. Orpiment has also been identified on Central Asian wall paintings from the sixth to the thirteenth centuries. In a traditional Thai painting technique, still in use today, yellow ink for writing and drawing on black paper manuscripts is made of orpiment.

Medieval European artists imported orpiment from Asia Minor. Orpiment has been identified on Norwegian wooden altar frontals, polychrome sculptures, and folk art objects, including a crucifix. It was also used in twelfth- to sixteenth-century icons from Bulgaria, Russia, and the former Yugoslavia. In Venice, orpiment was purchased for a Romanian prince in 1600. European uses of orpiment as a pigment were not common until the nineteenth century, during which orpiment was used as a pigment in impressionist paintings.

Orpiment as a pigment
Orpiment has been found in the painted Altar Frontal of the ancient Norwegian church of Tingelstad, which dates back to 1275-1300, and is among the earliest oil paintings to have survived.

Orpiment was commonly combined with Indigo to make a dark, rich green. A fine example of this is in The Wilton Diptych (c 1395-9), another very early European painting, this time in egg tempera. The green cloak at the left appears to have been painted using orpiment.

Renaissance artists such as Raphael Sanzio also used orpiment as a yellow pigment. The garments in Raphael’s Sistine Madonna from 1513-14 were painted using orpiment as yellow on the characters' clothes and in the back.

Tintoretto’s Portrait of Vincenzo Morosini from about 1575-80 is another example of the use of orpiment in its details. As shown in the detail below, to the right, orpiment used to form the brights on Morosini’s embroidered stole include small patches of the orange-red which is characteristic of Realgar.

Defects
Orpiment's extreme toxicity and incompatibility with other common pigments, including lead and copper-based substances such as verdigris and azurite, meant that its use as a pigment ended when cadmium yellows, chromium yellows and organic dye-based colors were introduced during the 19th century. Orpiment, both natural and artificial, was used until the end of the nineteenth century.

Other historical uses
Orpiment was traded in the Roman Empire and was used as a medicine in China, even though it is very toxic. It has been used as fly poison and to tip arrows with poison. For centuries, orpiment was ground down and used for sealing wax, and was even used in ancient China as a correction fluid. Because of its striking color, it was of interest to alchemists, both in China and the West, searching for a way to make gold. It also has been found in the wall decorations of Tutankhamun's tomb and ancient Egyptian scrolls, and on the walls of the Taj Mahal. In ancient Mesopotamia both orpiment and realgar are listed in Assyrian medical texts. Orpiment is mentioned in the 17th century by Robert Hooke in Micrographia for the manufacture of small shot. Scientists like Richard Adolf Zsigmondy and Hermann Ambronn puzzled jointly over the amorphous form of, "orpiment glass", as early as 1904.

Contemporary uses
Orpiment is used in the production of infrared-transmitting glass, oil cloth, linoleum, semiconductors, photoconductors, pigments, and fireworks. Mixed with two parts of slaked lime (calcium hydroxide), orpiment is still commonly used in rural India as a depilatory. It is used in the tanning industry to remove hair from hides.

Physical and optical properties
Orpiment is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.49. It melts at 300 °C to 325 °C. Optically, it is biaxial (−) with refractive indices of a = 2.4, b = 2.81, g = 3.02.