Lapis lazuli (UK: ; US: ) is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Its name originates from the Persian word for the gem, lāžward, and serves as the root for the word for "blue" in several languages, including Spanish and Portuguese azul and English azure. Lapis lazuli is a rock composed primarily of the minerals lazurite, pyrite, diopside, and calcite. As early as the 7th millennium BC, lapis lazuli was mined in the Sar-i Sang mines, in Shortugai, and in other mines in Badakhshan province in modern northeast Afghanistan. Lapis lazuli artifacts, dated to 7570 BC, have been found at Bhirrana, which is the oldest site of Indus Valley Civilisation. Lapis was highly valued by the Indus Valley Civilisation (3300–1900 BC). Lapis beads have been found at Neolithic burials in Mehrgarh, the Caucasus, and as far away as Mauritania. It was used in the funeral mask of Tutankhamun (1341–1323 BC). By the end of the Middle Ages, Europe began importing lapis lazuli to grind it into powder and make ultramarine pigment. Ultramarine was used by some of the most important artists of the Renaissance and Baroque, including Masaccio, Perugino, Titian and Vermeer; it was often reserved for the clothing of the central figures of their paintings, especially the Virgin Mary. Ultramarine has also been found in dental tartar of medieval nuns and scribes, perhaps as a result of licking their painting brushes while producing medieval texts and manuscripts.
History Excavations from Tepe Gawra show that lapis lazuli was introduced to Mesopotamia approximately in the late Ubaid period, c. 4900–4000 BCE. It became there the chief material for magic stones. A traditional understanding was that the Lapis lazuli was mined some 1,500 miles to the east – in Badakhshan. Indeed, the Persian لاژورد lāžavard/lāževard, also written لاجورد lājevard, is commonly interpreted as having an origin in a local place name. From the Persian, the Arabic لازورد lāzaward is the etymological source of both the English word azure (via Old French azur) and Medieval Latin lazulum, which came to mean 'heaven' or 'sky'. To disambiguate, lapis lazulī ("stone of lazulum") was used to refer to the stone itself, and is the term ultimately imported into Middle English. Lazulum is used as a root for the word for blue in several languages, including Spanish and Portuguese azul. Mines in northeast Afghanistan continue to be a major source of lapis lazuli. Important amounts are also produced from mines west of Lake Baikal in Russia, and in the Andes mountains in Chile which is the source that the Inca used to carve artifacts and jewelry. Smaller quantities are mined in Pakistan, Italy, Mongolia, the United States, and Canada.
Science and uses
Composition The most important mineral component of lapis lazuli is lazurite (typically 30% to 40%), a blue feldspathoid silicate mineral of the sodalite family, with the formula Na7Ca(Al6Si6O24)(SO4)(S3) ·H2O . Most lapis lazuli also contains calcite (white), and pyrite (metallic yellow). Some samples of lapis lazuli contain augite, diopside, enstatite, mica, hauynite, hornblende, nosean, and sulfur-rich löllingite geyerite. Lapis lazuli usually occurs in crystalline marble as a result of contact metamorphism.
Color
The intense blue color is due to the presence of the trisulfur radical anion (S•−3) in the crystal. The presence of disulfur (S•−2) and tetrasulfur (S•−4) radicals can shift the color towards yellow or red, respectively. These radical anions substitute for the chloride anions within the sodalite structure. The S•−3 radical anion exhibits a visible absorption band in the range 595–620 nm with high molar absorptivity, leading to its bright blue color.
Sources Lapis lazuli is found in limestone in the Kokcha River valley of Badakhshan Province in north-eastern Afghanistan, where the Sar-i Sang mine deposits have been worked for more than 6,000 years. Afghanistan was the source of lapis for the ancient Persian, Egyptian and Mesopotamian civilizations, as well as the later Greeks and Romans. Ancient Egyptians obtained the material through trade with Mesopotamians, as part of Egypt–Mesopotamia relations and from ancient Ethiopia . During the height of the Indus Valley Civilisation, approximately 2000 BC, the Harappan colony, now known as Shortugai, was established near the lapis mines. In addition to the Afghan deposits, lapis is also extracted in the Andes (near Ovalle, Chile); and to the west of Lake Baikal in Siberia, Russia, at the Tultui lazurite deposit. It is mined in smaller amounts in Angola, Argentina, Burma, Ethiopia, Pakistan, Canada, Italy, India, and in the United States in California and Colorado.
Uses and substitutes Lapis takes an excellent polish and can be made into jewellery, carvings, boxes, mosaics, ornaments, small statues, and vases. Interior items and finishing of buildings can be also made with lapis. During the Renaissance, lapis was ground and processed to make the pigment ultramarine for use in frescoes and oil painting. Its usage as a pigment in oil paint largely ended during the early 19th century, when a chemically identical synthetic variety became available. Lapis lazuli is commercially synthesized or simulated by the Gillson process, which is used to make artificial ultramarine and hydrous zinc phosphates. Spinel or sodalite, or dyed jasper or howlite, can be substituted for lapis.
History and art
In the ancient world
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