Lapis lazuli


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 BCE, lapis lazuli was mined in the Sar-i Sang mines, in Shortugai, and in other mines in Badakhshan province in northeast Afghanistan.
Lapis was highly valued by the Indus Valley Civilisation, and 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.
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. It 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.

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. Smaller quantities are mined in Pakistan, Italy, Mongolia, the United States, and Canada.

Etymology

Lapis is the Latin word for "stone" and lazulī is the genitive form of the Medieval Latin lazulum, which is taken from the Arabic لازورد lāzaward, itself from the Persian لاجورد lājevard, which is the name of the stone in Persian, and also of a place where lapis lazuli was mined. Lazulum is etymologically related to the color blue and used as a root for the word for blue in several languages, including Spanish and Portuguese azul.

Science and uses

Composition

The most important mineral component of lapis lazuli is lazurite, a feldspathoid silicate mineral with the formula 861-2. Most lapis lazuli also contains calcite, sodalite, and pyrite. 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. An electronic excitation of one electron from the highest doubly filled molecular orbital into the lowest singly occupied orbital results in a very intense absorption line at λmax ~617 nm.

Uses and substitutes

Lapis takes an excellent polish and can be made into jewelry, carvings, boxes, mosaics, ornaments, small statues, and vases. 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 Gilson process, which is used to make artificial ultramarine and hydrous zinc phosphates. It may also be substituted by spinel or sodalite, or by dyed jasper or howlite.

History and art

In the ancient world

Lapis lazuli has been mined in Afghanistan and exported to the Mediterranean world and South Asia since the Neolithic age, along the ancient trade route between Afghanistan and the Indus Valley, dating to the 7th millennium BCE. Quantities of these beads have also been found at 4th millennium BCE settlements in Northern Mesopotamia, and at the Bronze Age site of Shahr-e Sukhteh in southeast Iran. A dagger with a lapis handle, a bowl inlaid with lapis, amulets, beads, and inlays representing eyebrows and beards, were found in the Royal Tombs of the Sumerian city-state of Ur from the 3rd Millennium BCE.
Lapis was also used in ancient Mesopotamia by the Akkadians, Assyrians, and Babylonians for seals and jewelry. It is mentioned several times in the Mesopotamian poem, the Epic of Gilgamesh, one of the oldest known works of literature. The Statue of Ebih-Il, a 3rd millennium BCE statue found in the ancient city-state of Mari in modern-day Syria, now in the Louvre, uses lapis lazuli inlays for the irises of the eyes.
In ancient Egypt, lapis lazuli was a favorite stone for amulets and ornaments such as scarabs. Lapis jewelry has been found at excavations of the Predynastic Egyptian site Naqada. At Karnak, the relief carvings of Thutmose III show fragments and barrel-shaped pieces of lapis lazuli being delivered to him as tribute. Powdered lapis was used as eyeshadow by Cleopatra.
Jewelry made of lapis lazuli has also been found at Mycenae attesting to relations between the Myceneans and the developed civilizations of Egypt and the East.
In late classical times and as late as the Middle Ages, lapis lazuli was often called sapphire, though it had little to do with the stone today known as the blue corundum variety sapphire. In his book on stones, the Greek scientist Theophrastus described "the sapphirus, which is speckled with gold," a description which matches lapis lazuli.
There are many references to sapphires in the Old Testament, but most scholars agree that, since sapphire was not known before the Roman Empire, they most likely are references to lapis lazuli. For instance, Exodus 24:10: "And they saw the God of Israel, and there was under his feet as it were a paved work of a sapphire stone...". The term used in the Latin Vulgate Bible in this citation is "lapidus sapphiri", the term for lapis lazuli. Modern translations of the Bible, such as the New Living Translation Second Edition, refer to lapis lazuli in most instances instead of sapphire.