lapis lazuli

Lapis lazuli
A polished specimen of lapis lazuli.
General
Category	Rock
Chemical formula	mixture of minerals
Identification
Color	Blue, mottled with white calcite and brassy pyrite
Crystal habit	Compact, massive
Crystal system	None, as lapis is a rock. Lazurite, the main constituent, frequently occurs as dodecahedra
Cleavage	None
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 (pronounced /ˈlæpɪs ˈlæz(j)ʊlaɪ/ or /ˈlæzjʊli/ LAP-iss LAZ-yu-lye/lee^[1]) (sometimes abbreviated to lapis) is a relatively rare, semi-precious stone that has been prized since antiquity for its intense blue color.

Lapis lazuli has been mined in the Badakhshan province of Afghanistan for over 6,000 years, and trade in the stone is ancient enough for lapis jewelry to have been found at Predynastic Egyptian sites (as archaeologists have frequently stated, but lapis could also be found in, e.g. the Siwa Oasis in the Western Lybian desert), and lapis beads at neolithic burials in Mehrgarh, the Caucasus, and even as far from Afghanistan as Mauritania.^[2]

Description

Rough and polished Lapis lazuli.

Lapis lazuli is a rock, not a mineral: whereas a mineral has only one constituent, lapis lazuli is formed from more than one mineral.^[3]

The main component of lapis lazuli is lazurite (25% to 40%), a feldspathoid silicate mineral composed of sodium, aluminium, silicon, oxygen, sulfur, and chloride. Its formula is (Na,Ca)₈(AlSiO₄)₆(S,SO₄,Cl)_1-2.^[4] Most lapis lazuli also contains calcite (white), sodalite (blue), and pyrite (metallic yellow). Other possible constituents are augite, diopside, enstatite, mica, hauynite, hornblende, and nosean. Some contain trace amounts of the sulfur rich lollingite variety geyerite.

Lapis lazuli usually occurs in crystalline marble as a result of contact metamorphism.

The finest color is intense blue, lightly dusted with small flecks of golden pyrite. Stones with no white calcite veins and only small pyrite inclusions are more prized. Patches of pyrite are an important help in identifying the stone as genuine and do not detract from its value. Often, inferior lapis is dyed to improve its color, producing a very dark blue with a noticeable grey cast which may also appear as a milky shade.

Uses

An Elephant carving in high quality lapis lazuli, showing gold-colored inclusions of pyrite. The carving is 8 cm (3.1 in) long.

Lapis takes an excellent polish and can be made into jewelry, carvings, boxes, mosaics, ornaments, and vases. In architecture it has been used for cladding the walls and columns of palaces and churches.

It was also ground and processed to make the pigment ultramarine for tempera paint and, more rarely, oil paint. Its usage as a pigment in oil paint ended in the early 19th century as a chemically identical synthetic variety, often called French Ultramarine, became available.

Etymology

Lapis is the Latin for 'stone' and lazuli the genitive form of the Medieval Latin lazulum, which is from the Arabic lāzaward, which is ultimately from the Persian لاژورد lāzhvard, the name of a place where lapis lazuli was mined.^[5][6] The name of the place came to be associated with the stone mined there and, eventually, with its color. The English word azure, the French azur, the Spanish and Portuguese azul, and the Italian azzurro are cognates. Taken as a whole, lapis lazuli means 'stone of Lāzhvard'.

Sources

The best lapis lazuli is found in limestone in the Kokcha River valley of Badakhshan province in northeastern Afghanistan, and these deposits in the mines of Sar-e-Sang have been worked for more than 6,000 years.^[7] Afghanistan was the source of lapis for the ancient Egyptian and Mesopotamian civilizations, as well as the later Greek and Roman; during the height of the Indus valley civilization about 2000 B.C., the Harappan colony now known as Shortugai was established near the lapis mines.^[2]

In addition to the Afghan deposits, lapis has been extracted for years in the Andes near Ovalle, Chile, where the deep blue stones compete in quality with those from Afghanistan.^[8] Other less important sources include the Lake Baikal region of Russia, Siberia, Angola, Burma, Pakistan, USA (California and Colorado), Canada, and India.

Historical usage

In ancient Egypt lapis lazuli was a favorite stone for amulets and ornaments such as scarabs; it was also used by the Assyrians and Babylonians for seals. Lapis jewelry has been found at excavations of the Predynastic Egyptian site Naqada (3300–3100 BC), and powdered lapis was used as eyeshadow by Cleopatra.^[2]

In ancient times, lapis lazuli was known as sapphire,^[9] which is the name that is used today for the blue corundum variety sapphire.

A Mesopotamian lapis lazuli pendant circa 2900 BCE.

A 11 cm (4.3 in) long lapis lazuli dove studded with gold pegs. Elamite. Dated 1200BCE from Susa, Iran. Carved lapis lazuli of a mountain scene, from the Chinese Qing Dynasty (1644–1912).

See also

• Kamboja-Dvaravati Route
• Lapis armenus

Notes

References

• Bowersox, Gary W.; Chamberlin, Bonita E. (1995), Gemstones of Afghanistan, Tucson, AZ: Geoscience Press .
• Oldershaw, Cally (2003), "Lapis Lazuli", Firefly Guide to Gems, Toronto: Firefly Books .

External links

• Lapis lazuli at Gemstone.org
• "The Use of Lapis Lazuli as a Pigment in Medieval Europe"
• Documentation from online course produced by University of California at Berkeley
• Lapis Lazuli from Afghanistan, Sar-e-Sang Mine, Jurm, Afghanistan

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