Lapis lazuli

Lapis lazuli

Lapis lazuli from Afghanistan in its natural state
General
Category Metamorphic rock
Formula
(repeating unit)		 mixture of minerals with lazurite as the main constituent.
Crystal system None, as lapis is a rock. Lazurite, the main constituent, frequently occurs as dodecahedra
Identification
Color Blue, mottled with white calcite and brassy pyrite
Crystal habit Compact, massive
Fracture Uneven-Conchoidal
Mohs scale hardness 5–5.5
Luster dull
Streak light blue
Specific gravity 2.7–2.9
Refractive index 1.5
Other characteristics The variations in composition cause a wide variation in the above values.

Lapis lazuli (/ˈlæpɪs ˈlæzjuːli/, /-ˈlæzjuːlaɪ/), 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,[1] in Shortugai, and in other mines in Badakhshan province in northeast Afghanistan.[2] 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 even as far from Afghanistan as Mauritania.[3] It was used in the funeral mask of Tutankhamun (1341–1323 BC).[4]

At 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.

Today, mines in northeast Afghanistan and Pakistan are still the 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 Italy, Mongolia, the United States, and Canada.[5]

Etymology

Lapis is the Latin word for "stone" and lazuli is the genitive form of the Medieval Latin lazulum, which is taken from the Arabic لاجورد lājaward, itself from the Persian لاجورد lājavard, which is the name of the stone in Persian[6] and also of a place where lapis lazuli was mined.[7][8]

The name "Lapis lazuli" came to be associated with its color. The English word azure, French azur, Italian azzurro, Polish lazur, Romanian azur and azuriu, Portuguese and Spanish azul, and Hungarian azúr all come from the name and color of lapis lazuli.

Science and uses

Composition

The most important mineral component of lapis lazuli is lazurite[9] (25% to 40%), a feldspathoid silicate mineral with the formula (Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2.[10] 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 (S
3) radical anion in the crystal.[11] An electronic excitation of one electron from the highest doubly filled molecular orbital (No. 24) into the lowest singly occupied orbital (No. 25)[12] results in a very intense absorption line at λmax ~617 nm.

Sources

Lapis lazuli is found in limestone in the Kokcha River valley of Badakhshan province in northeastern Afghanistan, where the Sar-e-Sang mine deposits have been worked for more than 6,000 years.[13] Afghanistan was the source of lapis for the ancient Egyptian and Mesopotamian civilizations, as well as the later Greeks and Romans. Ancient Egyptians obtained this material through trade from Afghanistan. During the height of the Indus Valley Civilisation about 2000 BC, the Harappan colony now known as Shortugai was established near the lapis mines.[3]

According to the Sorbonne's mineralogist Pierre Bariand's leading work on the sources of lapis lazuli in modern times, and to references in Afghanistan's Blue Treasure: Lapis Lazuli (2011) by Lailee McNair Bakhtiar, the lapis lazuli is found in "caves" not traditionally considered "mines" and the stone lapis lazuli is from the primary source of the Hindu Kush Mountains in Afghanistan's Kochka River Valley and not in Pakistan.

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.[5]

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 in 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.[14] It may also be substituted by spinel or sodalite, or by dyed jasper or howlite.[15]

History and art

In the ancient world

Naqada I (Egypt) female figure, circa 3700 BC. Bone with Lapis inlay from Badakhshan.

Lapis lazuli has been mined in Afghanistan and exported to the Mediterranean world and South Asia since the Neolithic age.[16] Lapis lazuli beads have been found at Mehrgarh, a neolithic site near Quetta in Pakistan, on 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, and 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.[16]

Lapis was also used in ancient Mesopotamia by the Akkadians, Assyrians, and Babylonians for seals and jewelry. In the Mesopotamian poem the Epic of Gilgamesh (17th-18th Century BC), one of the oldest known works of literature, lapis lazuli is mentioned several times. 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.[17]

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 (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.[3][18]

In late classical times and as late as the Middle Ages, lapis lazuli was often called sapphire (sapphirus in Latin, sappir in Hebrew),[19] 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.[20]

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: "As they saw the God of Israel, and there was under his feet as it were a paved work of a sapphire stone.." (KJV). The term used in the Latin Vulgate Bible in this citation is "lapidus sapphiri," the term for lapis lazuli.[21] Modern translations of the Bible, such as the New Living Translation Second Edition,[22] refer to lapis lazuli in most instances instead of sapphire.

See also

References

Notes and citations

  1. ↑ David Bomford and Ashok Roy, A Closer Look- Colour (2009), National Gallery Company, London, (ISBN 978-1-85709-442-8)
  2. ↑ Moorey, Peter Roger (1999). Ancient Mesopotamian Materials and Industries: the Archaeological Evidence. Eisenbrauns. pp. 86–87. ISBN 978-1-57506-042-2.
  3. 1 2 3 Bowersox & Chamberlin 1995
  4. ↑ Alessandro Bongioanni & Maria Croce
  5. 1 2 "All about colored gemstones," the International Colored Gemstones Association
  6. ↑ Oxford English Dictionary
  7. ↑ Senning, Alexander (2007). "lapis lazuli (lazurite)". Elsevier's Dictionary of Chemoetymology. Amsterdam: Elsevier. p. 224. ISBN 978-0-444-52239-9.
  8. ↑ Weekley, Ernest (1967). "azure". An Etymological Dictionary of Modern English. New York: Dover Publications. p. 97.
  9. ↑ Mindat entry relating to lapis lazuli
  10. ↑ Mindat – Lazurite
  11. ↑ Boros, E.; Earle, M. J.; Gilea, M. A.; Metlen, A.; Mudring, A.-V.; Rieger, F.; Robertson, A. J.; Seddon, K. R.; Tomaszowska, A. A.; Trusov, L.; Vyle, J. S. (2010). "On the dissolution of non-metallic solid elements (sulfur, selenium, tellurium and phosphorus) in ionic liquids". Chem. Comm. 46: 716–718. doi:10.1039/b910469k.
  12. ↑ H. S. Rzepa, "Lapis lazuli: the Colour of Ultramarine." Accessed: 2011-03-06. (Archived by WebCite® at https://www.webcitation.org/5wyiNxh3B)
  13. ↑ Oldershaw 2003
  14. ↑ Read, Peter (2005). Gemmology, Elsevier, p. 185. ISBN 0-7506-6449-5
  15. ↑ Lapis lazuli, Gemstone Buzz.
  16. 1 2 Moorey, Peter Roger (1999). Ancient mesopotamian materials and industries: the archaeological evidence. Eisenbrauns. pp. 86–87. ISBN 978-1-57506-042-2.
  17. ↑ Claire, Iselin. "Ebih-Il, the Superintendent of Mari". Musée du Louvre. Retrieved 10 October 2012.
  18. ↑ Moment of Science site, Indiana Public Media
  19. ↑ Schumann, Walter (2006) [2002]. "Sapphire". Gemstones of the World. trans. Annette Englander & Daniel Shea (newly revised & expanded 3rd ed.). New York: Sterling. p. 102. In antiquity and as late as the Middle Ages, the name sapphire was understood to mean what is today described as lapis lazuli.
  20. ↑ Theoprhastus, On Stones (De Lapidibus) - IV-23, translated by D.E. Eichholtz, Oxford University Press, 1965.
  21. ↑ Pearlie Braswell-Tripp (2013), Real Diamonds and Precious Stones of the Bible (ISBN 978-1-4797-9644-1)
  22. ↑ "In His Image Devotional Bible" (IBN 978-1-4143-3763-0)

Bibliography

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