pigment containing hematite and historically produced with the use of mummified corpses. Some of its compositions produce a purple color and may be called "mummy violet". Manganese was also used in Roman times to color glass purple. Han purple was the first synthetic purple pigment, invented in China in about 700 BC. It was used in wall paintings and pottery and other applications. In color, it was very close to indigo, which had a similar chemical structure. Han purple was very unstable, and sometimes was the result of the chemical breakdown of Han blue. During the Middle Ages, artists usually made purple by combining red and blue pigments; most often blue azurite or lapis-lazuli with red ochre, cinnabar, or minium. They also combined lake colors made by mixing dye with powder; using woad or indigo dye for the blue, and dye made from cochineal for the red. Cobalt violet was the first modern synthetic color in the purple family, manufactured in 1859. It was found, along with cobalt blue, in the palette of Claude Monet, Paul Signac, and Georges Seurat. It was stable, but had low tinting power and was expensive, so quickly went out of use. Manganese violet was a stronger color than cobalt violet, and replaced it on the market. Quinacridone violet, one of a modern synthetic organic family of colors, was discovered in 1896 but not marketed until 1955. It is sold today under a number of brand names. Dyes The most famous purple dye in the ancient world was Tyrian purple, made from a type of sea snail called the murex, found around the Mediterranean. (See history section above). In western Polynesia, residents of the islands made a purple dye similar to Tyrian purple from the sea urchin. In Central America, the inhabitants made a dye from a different sea snail, the purpura, found on the coasts of Costa Rica and Nicaragua. The Mayans used this color to dye fabric for religious ceremonies, while the Aztecs used it for paintings of ideograms, where it symbolized royalty. In the Middle Ages, those who worked with blue and black dyes belonged to separate guilds from those who worked with red and yellow dyes, and were often forbidden to dye any other colors than those of their own guild. Most purple fabric was made by the dyers who worked with red, and who used dye from madder or cochineal,