Lapis lazuli: Difference between revisions
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Image:Lapis lazuli p1070260.jpg|Carved lapis lazuli mountain scene, from the Chinese [[Qing Dynasty]] (1644–1912). |
Image:Lapis lazuli p1070260.jpg|Carved lapis lazuli mountain scene, from the Chinese [[Qing Dynasty]] (1644–1912). |
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Image:Lapis.elephant.800pix.060203.jpg|An elephant carving in high-quality lapis lazuli, showing gold-colored inclusions of [[pyrite]] (length {{convert|8|cm|in|abbr=on|lk=off}}) |
Image:Lapis.elephant.800pix.060203.jpg|An elephant carving in high-quality lapis lazuli, showing gold-colored inclusions of [[pyrite]] (length {{convert|8|cm|in|abbr=on|lk=off}}) |
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Image:LapisLazuli.JPG |A small sample of uncut lapis lazuli. |
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Revision as of 01:07, 24 December 2010
| Lapis lazuli | |
|---|---|
 A polished specimen of lapis lazuli. | |
| General | |
| Category | Rock |
| Formula (repeating unit) | mixture of minerals |
| 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 |
| 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 (Template:Pron-en or /ˈlæzjʉli/ LAP-iss LAZ-ew-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 from mines in the Badakhshan province of Afghanistan for over 6,000 years and there are sources that are found as far east as in the region around Lake Baikal in Siberia. Trade in the stone is ancient enough for lapis jewelry to have been found at Predynastic Egyptian sites, and as lapis beads at neolithic burials in Mehrgarh, the Caucasus, and even as far from Afghanistan as Mauritania.[2]
Description
Lapis lazuli is a rock, largely formed from the mineral lazurite.[3]
The main component of lapis lazuli is lazurite (25% to 40%), a feldspathoid silicate mineral with formula: (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: augite; diopside; enstatite; mica; hauynite; hornblende, and nosean. Some lapis lazuli contains trace amounts of the sulfur-rich löllingite 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.[citation needed] 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.[citation needed]
Uses
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.[citation needed]
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 when 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 [لازورد lāzaward] Error: {{Transliteration}}: transliteration text not Latin script (pos 1) (help), which is ultimately from the Persian لاژورد lāzhward, 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 Italian azzurro, the Spanish and the Portuguese azul are cognates. Taken as a whole, lapis lazuli means "stone of Lāzhward".
Sources
The best 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.[7] Afghanistan was the source of lapis for the ancient Egyptian and Mesopotamian civilizations, as well as the later Greeks and Romans. During the height of the Indus valley civilization about 2000 BC, 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 many years in the Andes (near Ovalle, Chile), the Lake Baikal region of Russia; Siberia; Angola; Burma; Pakistan; Canada; India; and in the USA in California and Colorado.
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,[8] which is the name that is used today for the blue corundum variety sapphire.
A Chinese carving inspired William Butler Yeats's poem "Lapis Lazuli".
Alternatives
Lapis lazuli is commercially "synthesized" (actually simulated) by the Gilson process, using artificial ultramarine and hydrous zinc phosphates.[9] It may be substituted by spinel or sodalite, or by dyed jasper or howlite.[10]
Gallery
-
A Mesopotamian lapis lazuli pendant circa 2900 BC. -
-
Carved lapis lazuli mountain scene, from the Chinese Qing Dynasty (1644–1912). -
An elephant carving in high-quality lapis lazuli, showing gold-colored inclusions of pyrite (length 8 cm (3.1 in)) -
A small sample of uncut lapis lazuli.
See also
Notes
- ^ *The New Penguin English Dictionary, 2000
- ^ a b c Bowersox & Chamberlin 1995
- ^ Mindat entry relating to lapis lazuli
- ^ Mindat - Lazurite
- ^ Senning, Alexander (2007). "lapis lazuli (lazurite)". Elsevier's Dictionary of Chemoetymology. Amsterdam: Elsevier. p. 224. ISBN 9780444522399.
{{cite book}}: Cite has empty unknown parameter:|coauthors=(help) - ^ Weekley, Ernest (1967). "azure". An Etymological Dictionary of Modern English. New York: Dover Publications. p. 97.
{{cite book}}: Cite has empty unknown parameter:|coauthors=(help) - ^ Oldershaw 2003
- ^ 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.
- ^ Gemmology by Peter Read, page 185.
- ^ http://www.gemstonebuzz.com/lapis-lazuli Lapis lazuli at Gemstone Buzz.
References
- Bowersox, Gary W.; Chamberlin, Bonita E. (1995). "Gemstones of Afghanistan" (Document). Geoscience Press.
{{cite document}}: Invalid|ref=harv(help); Unknown parameter|publication-place=ignored (help). - Oldershaw, Cally (2003). "Firefly Guide to Gems" (Document). Toronto: Firefly Books.
{{cite document}}: Invalid|ref=harv(help); Unknown parameter|contribution=ignored (help).
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
- Lapislzuli - occurrence, mining and market potential of a classic blue mineral pigment pdf, in german