Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. 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 (7570–1900 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, lapis lazuli began to be exported to Europe, where it was ground into powder and made into ultramarine, the finest and most expensive of all blue pigments. Ultramarine was used by some of the most important artists of the Renaissance and Baroque, including Masaccio, Perugino, Titian and Vermeer, and 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.
Major sources
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.
Etymology
is the Latin word for "stone" and is the genitive form of the Medieval Latin , which is taken from the Arabic , itself from the Persian . It means "sky" or "heaven"; so this is a "stone (of/from) the sky" or "stone (of/from) heaven". For example, in the following Persian poem by Ferdowsi:
As the sun struck the dome of lazuli,
A golden curtain was drawn, most truly.
Historically, it was mined in the Badakhshan region of upper Afghanistan. is etymologically related to the color blue, and used as a root for the word for blue in several languages, including Spanish and Portuguese as well as English .
Science and uses
Composition
The most important mineral component of lapis lazuli is lazurite (25% to 40%), a blue feldspathoid silicate mineral with the formula . Most lapis lazuli also contains calcite (white), sodalite (blue), 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 () in the crystal. The presence of disulfur () and tetrasulfur () radicals can shift the color towards yellow or red, respectively. These radical anions substitute for the chloride anions within the sodalite structure. The 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 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. 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, Pakistan, Canada, Italy, India, and in the United States in California and Colorado.