The word "manuscript" comes from the Latin words "manus" (hand) and "scriptus," from scribere (to write). Today the word "manuscript" is used to describe any hand written text. The word "illumination" derives from the Latin verb "illuminare" (to adorn), which refers to hand-painted decorations on the manuscript. Many colors were used to decorate manuscripts, such as silver, gold, and other precious metals. Illuminations also decorate letters,... borders, and figurative scenes, which is known as a miniature. Although paper was abundant in Europe by the fourteenth century, manuscripts were typically written on vellum. Vellum is a high-quality type of parchment made from specially prepared skins of calves, sheep, or goats. Vellum continued to be used for many years in Europe for its texture, translucency, and for its durability. The text of a manuscript was typically written in ink made from an extract of gallnuts mixed with iron sulfate and gum Arabic. When this ink was applied to vellum, its iron content oxidized and the ink changed to a brownish color. Miniatures were often painted with a variety of precious colors, such as vermilion and ultramarine blue. Vermilion was produced from combining mercury and sulfur. Ultramarine blue was made by crushing lapis lazuli and is considered to be as expensive as gold. Sometimes miniatures were decorated with gold leaf by applying it in thin sheets. However, in the later Middle Ages, artists tended to substitute gold leaf with gold paint. Traditionally, illuminations were devoted to religious works and were produced in monasteries, particularly in the "scriptorium," which was the center for scholarly studies and copying of texts. Later, as book illumination became more valued, lay artists were hired to collaborate with monastic scribes. With the rise of universities in the twelfth century, scribes and illuminators became professional laymen who made their living by producing fine manuscripts for noblemen, for the new middle class, and for the emerging universities in cities such as Paris, Bologna, and Padua. Moreover, some religious communities also began to copy manuscripts on a commercial basis.