|Lapis Lazuli: Composition and Color. Polished Lapis lazuli. Photo: New Moon Beginnings|
Lapis lazuli is a blue metamorphic rock that has been used by people as a gemstone, sculpting material, and ornamental material for thousands of years.
The most important mineral component of lapis lazuli is lazurite (25% to 40%), a feldspathoid silicate mineral with the formula (Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2. 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.
Lazurite is a tectosilicate mineral with sulfate, sulfur and chloride with formula: (Na,Ca)8[(S,Cl,SO4,OH)2|(Al6Si6O24)]. It is a feldspathoid and a member of the sodalite group. Lazurite crystallizes in the isometric system although well formed crystals are rare. It is usually massive and forms the bulk of the gemstone lapis lazuli.
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.
|Rough lapis. Photo: Arsaa Gems And Minerals|
High-quality lapis lazuli has been used as a mineral pigment for over 1,000 years. Bright blue pieces of lapis are trimmed of impurities and ground to a fine powder; the powder can then be mixed with oil or another vehicle for use as a paint.
Where is Lapis Lazuli Found?Lapis lazuli was discovered around 6,000 years ago in the West Hindu-Kush Mountains of present-day Afghanistan. Today, Afghanistan continues to be the leading producer of the gem. Other countries involved in production include Angola, Argentina, Canada, Chile, India, Italy, Myanmar, Pakistan, the United States, and Russia.
UltramarineUltramarine is a deep blue color pigment which was originally made by grinding lapis lazuli into a powder. The name comes from the Latin ultramarinus, literally "beyond the sea", because the pigment was imported into Europe from mines in Afghanistan.
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