In the 1950s, a new family of violet synthetic organic pigments called quinacridones came onto the market. They had originally been discovered in 1896, synthesized in 1936 and manufactured in the 1950s. The colors in the group range from deep red to violet in color, and have the molecular formula C20H12N2O2. They have strong resistance to sunlight and washing, and are used in oil paints, water colors and acrylics, as well as in automobile coatings and other industrial coatings. Zoology Botany In history and art Prehistory and antiquity Violet is one of the oldest colors used by humans. Traces of very dark violet, made by grinding the mineral manganese, mixed with water or animal fat and then brushed on the cave wall or applied with the fingers, are found in the prehistoric cave art in Pech Merle, in France, dating back about 25,000 years. It has also been found in the cave of Altamira and Lascaux. It was sometimes used as an alternative to black charcoal. Sticks of manganese, used for drawing, have been found at sites occupied by Neanderthals in France and Israel. From the grinding tools at various sites, it appears it may also have been used to color the body and to decorate animal skins. More recently, the earliest dates on cave paintings have been pushed back farther than 35,000 years. Hand paintings on rock walls in Australia may be even older, dating back as far as 50,000 years. Berries of the genus rubus, such as blackberries, were a common source of dyes in antiquity. The ancient Egyptians made a kind of violet dye by combining the juice of the mulberry with crushed green grapes. The Roman historian Pliny the Elder reported that the Gauls used a violet dye made from bilberry to color the clothing of slaves. These dyes made a satisfactory purple, but it faded quickly in sunlight and when washed. Middle Ages and Renaissance Violet and purple retained their status as the color of emperors and princes of the church throughout the long rule of the Byzantine Empire. While violet was worn less frequently by Medieval and Renaissance kings and princes, it was worn by the professors of many of Europe's new universities. Their robes were modeled after those of the clergy, and they often wore square violet caps and violet robes, or black robes with violet trim. Violet also played an important part