Lapis lazuli is a relatively rare, semi-precious stone which has been prized for its intense blue color since antiquity. The metamorphic rock is a mixture of the blue mineral lazurite, white calcspar and golden iron pyrites. Through extensive grinding, washing, sieving, and a lavish process of multiple extraction, lapis lazuli is turned into the costly natural pigment ultramarine (Latin “ultramarinus”, literally for “beyond the sea” because was imported from Asia) known for its pure bright blue color and fine quality. Because of its high price during the Middle Ages (it was once more expensive than gold), lapis lazuli was used only for certain parts in the most precious paintings, e. g. the robe of the Virgin Mary thus indicating her spiritual importance. There are several grades of diminishing quality: While the largest and most deeply colored particles emerge in the first extraction, the last extraction produces a high proportion of colorless material, known as ultramarine ash, and valued as a blue glazing pigment. There are two areas where lapis lazuli is found: It has been mined in Afghanistan for more than 8,000 years, and in Chile since the 20th century.
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