Lapis lazuli

Lapis lazuli  is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, lāžward, lapis lazuli is a rock composed primarily of the minerals lazurite, pyrite 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, Lapis lazuli began to be exported to Europe, where it was ground into powder and made into the pigment ultramarine. 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.

Lapis lazuli

Composition

Primary Lazurite

Secondary A mixture of other minerals, often including pyrite

History

Excavations from Tepe Gawra show that Lapis lazuli was introduced to Mesopotamia approximately in the late Ubaid period, c. 4900–4000 BCE. A traditional understanding was that the Lapis lazuli was mined some fifteen hundred 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 etymologically related to the color blue, and 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 (25% 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.

Chemistry

The first characterizations of this mineral color pigment were carried out by Andreas Sigismund Marggraf in 1768.  The first chemical analysis of the main component of lapis lazuli, the azurite, was carried out in 1806 by the French chemist Nicolas Clément with what is considered a good level of accuracy by today's standards (silica: 35.8%, alumina: 34.8%, soda: 23.2%, soda: 3.1%, carbonate: 3.1%). Based on this, methods for producing artificial ultramarine, which should correspond as closely as possible to natural lazurite, were subsequently sought. This method was developed almost simultaneously in the 1820s by the French chemist Jean-Baptiste Guimet and the German chemist Christian Gottlob Gmelin. Investigations of natural and artificial ultramarine and the related minerals sodalite, nosean and hauyne using physical methods (from 1929 using X-ray structural analysis) led to the realization that these substances belong to the group of aluminosilicates. 

Desired gemstones have an intense, ultramarine blue color, which is due to S 3 − radical anions of sulfur in the idealized formula Na 6 [Al 6 Si 6 O 24 ]S x Ca (where x > 1). Finely distributed pyrite is considered a sign of authenticity. Spots or small golden pyrite veins are also prized, but the pyrite content should not be too high, as otherwise the color turns an unsightly green. Stones in which the calcite is very prominent are less valuable.

The different deposits produce different color nuances. Tajik lapis lazuli is more marine blue, while those found at Lake Baikal exhibit blue-violet tones and particularly strong calcite content.

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

Lapis takes an excellent polish and can be made into jewellery, carvings, boxes, mosaics, ornaments, small statues, and vases. Interior items and finishing 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.

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 BC. Quantities of these beads have also been found at 4th millennium BC settlements in Northern Mesopotamia, and at the Bronze Age site of Shahr-e Sukhteh in southeast Iran (3rd millennium BC). 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 BC.

Lapis was also used in ancient Persia, Mesopotamia by the Akkadians, Assyrians, and Babylonians for seals and jewelry. It is mentioned several times in the Mesopotamian poem, the Epic of Gilgamesh (17th–18th century BC), one of the oldest known works of literature. The Statue of Ebih-Il, a 3rd millennium BC 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 jewellery has been found at excavations of the Predynastic Egyptian site Naqada (3300–3100 BC). At Karnak, the relief carvings of Thutmose III (1479–1429 BC) 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.

Pliny the Elder wrote that lapis lazuli is "opaque and sprinkled with specks of gold". Because the stone combines the blue of the heavens and golden glitter of the sun, it was emblematic of success in the old Jewish tradition. In the early Christian tradition lapis lazuli was regarded as the stone of Virgin Mary.

In late classical times and as late as the Middle Ages, lapis lazuli was often called sapphire (sapphirus in Latin, sappir in Hebrew), 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 "sapphire" 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..." (KJV). The words used in the Latin Vulgate Bible in this citation are "quasi opus lapidis sapphirini", the terms 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.

Use in the Middle Ages and modern times

Lapis lazuli has been used as a gemstone since prehistoric times, at least 7,000 years ago . Genuine lapis lazuli often contains shimmering golden pyrite particles.

Exposed examples of the use of lapis lazuli gemstones continue into modern times. The canonized Saint Aloysius Gonzaga (d. 1591) was buried in a lapis lazuli urn. In the Church of Il Gesù in Rome (c. 1700), the altar of the St. Ignatius Chapel was decorated with lapis lazuli columns and a lapis-blue globe set in gold. For a long time, the globe was considered the largest work of art created from a block of lapis. However, recent research shows that it was mortar with a high lapis lazuli content. The central columns of the iconostasis in St. Isaac's Cathedral in St. Petersburg (c. 1800) are made of this stone. In the Potsdam Orangery Palace (built between 1851 and 1864), Frederick William IV had a lapis lazuli room built, the furniture of which is decorated with gemstones. A lapis lazuli monolith from Chile weighing 18.3 tons, the largest ever recovered, was used to create the Water Waves of Life Fountain in Vienna at the end of the 20th century.

Lapis lazuli played a major role in Western art as a pigment for bright blue and lightfast paint. Its sparing use in medieval paintings, however, is due to the fact that the pigment was extremely expensive. As the name " ultramarine " suggests, it had to be obtained from traders "across the sea." The price per ounce for this high-quality, vibrant blue pigment during the Renaissance was roughly equivalent to that of gold.

For a long time, the use of lapis lazuli as a pigment in addition to indigo in the Scottish Book of Kells (c. 800) was assumed. However, more recent analyses have shown that the blue color was extracted from woad. In the Codex aureus Epternacensis and other works of Ottonian illumination, the heavenly sphere was given a material aesthetic, while less important details were painted with azurite. Since the Quattrocento, the early Italian Renaissance, lapis lazuli and gold were explicitly recorded in contracts between painters and clients, particularly as blue in the design of the Virgin Mary's robe. 

The technique for obtaining the pigment is known from the records of Cennino Cennini (c. 1400). The bright blue sky in the paintings of Fra Angelico or Giotto's frescoes in the Cappella degli Scrovegni (Padua) was also painted with filtered lapis lazuli as a pigment. Examples of its use as a color base can be found in the Book of Hours of the Duke of Berry, one of the most important works of book illumination from the 15th century. Archaeological traces have also been found in the tartar of a woman from the 12th century and are considered to be traces of book art. Albrecht Dürer used ultramarine for a number of his commissioned works. In a letter to the patron of the " Heller Altar ", he emphasizes the high cost of the material, stating that an ounce of fine ultramarine cost him ten to twelve ducats. 

In Muslim architecture in Central Asia, lapis lazuli pigment was used for bright blue faience tiles, for example at the Bibi-Khanym Mosque and the Ulugbek Madrasa in Samarkand or the Mir-i Arab Madrasa in Bukhara. The material came from deposits in the Kokcha Valley in northern Afghanistan and was traded westward along the Silk Road. 

Lapis lazuli has been documented on pottery for the Lajvardina ware (Persian: Lajvard, "lapis lazuli") of Persia from the 12th to 14th centuries, as well as on Meissen porcelain from the 18th century.  With the discovery of a process for producing synthetic ultramarine blue in 1828, the natural pigment increasingly lost its economic importance in Europe. Friedrich August Köttig developed the artificial "Meissen azure stone blue", a cost-effective method for producing deep blue porcelain colors.

The natural lapis lazuli pigment, which remains very expensive due to its laborious extraction, is valued in Europe, especially by restorers. In East Asia (especially Japan and China) and Arabia, the high esteem for natural ultramarine as a "heavenly" and thus royal blue remains unbroken. The Japanese artist Hiroshi Ōnishi created a series of paintings with lapis lazuli pigments, for example for the Nanzen-ji Temple in Kyoto.

Ground into a fine powder, it has long been used as a blue pigment for painting, initially in frescoes (cave temples of Bamiyan in Afghanistan, frescoes in the Kizil caves in Chinese Turkestan and in India). Powdered lapis was also used in Persian miniatures in the 13th and 14th centuries.

Ultramarine pigment, extracted from lapis lazuli, was used from the 12th century onwards in miniatures (manuscripts from the Abbey of Saint-Germain d'Auxerre and the Abbey of Fécamp). When refined, it becomes very colorful and can be used with inferior qualities. It was then widely used in painting, in tempera and then in oil painting. It was imported from Venice, hence its regular use by Italian painters, particularly those of the 14th and 15th centuries.

In 1303, the painter Giotto was called to Padua, where he painted the fifty-three frescoes of the Scrovegni Chapel or Chapel of Santa Maria dell'Arena, which are considered his masterpiece and one of the turning points in the history of European painting. He was probably around forty years old when he began the decoration of the chapel, completed in 1306, where he painted frescoes depicting the life of Christ, which are one of the peaks of Christian art.

Similarly, true ultramarine would have been used to paint the sky on the ceiling of the Sistine Chapel, the frescoes of the chapels of St Martial and St John in the Palace of the Popes in Avignon as well as the ornaments of the Nasrid palaces of Granada in Muslim Spain.

It was then very expensive (more expensive than gold at certain times). Painters therefore used it as a final layer, on a less expensive blue background (indigo, azurite).

Johannes Vermeer used lapis lazuli paint, in the Girl with a Pearl Earring painting. The poet, William Butler Yeats, describes a figurine of sculpted lapis lazuli in a poem entitled "Lapis Lazuli". The sculpture of three men from China, a bird, and a musical instrument serves in the poem as a reminder of "gaiety" in the face of tragedy.

Manipulations and imitations

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.

A washed azurite was formerly called Lapis Lazuli ablutus in Latin. 

Pale lapis lazuli is oiled or waxed to make it appear darker. Uneven coloration can be evened out with colored oil, but this is easily detectable with acetone. 

Lapis lazuli of low quality or in small fragments is reconstructed into larger stones using synthetic resin.

Imitations of lapis lazuli are primarily produced by coloring the quartz variety jasper with Prussian blue. Thus, the so-called "German Lapis(lazuli)" is made from jasper in Nunkirchen (town of Wadern); other names include "Swiss Lapis," "Blue Onyx, " or "Nunkirchen Lapis Lazuli." If such inferior imitations of gemstones are treated in an ultrasonic bath or with ammonia, stains appear on the stone's surface that cannot be removed because the coloring pigment has been dissolved.

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