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Lapis lazuli

From Academic Kids

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Lapis_lazuli_block.jpg
A block of lapis lazuli

Lapis lazuli is one of the stones with the longest tradition of being considered a gem, with a history stretching back 7,000 years. Deep blue in color and opaque, this gemstone was highly prized by the pharaohs of ancient Egypt, as can be seen by its prominent use in many of the treasures recovered from pharaonic tombs. It is still extremely popular today.

The finest lapis has traditionally come from the Badakshan area of Afghanistan. This source of lapis may be the oldest continually worked set of mines in the world, the same mines operating today having supplied the lapis of the pharaohs. More recently, during the Soviet war in Afghanistan, Afghani resistance fighters disassembled unexploded Russian landmines and ordnance and used the scavenged explosive to help mine lapis to further fund their resistance efforts.

In addition to the Afghan deposits, lapis has been found in Pakistan and (in lower qualities) in the Andes Mountains of Chile.

Lapis is a rock and not a mineral because it is made up from various other minerals. To be a true mineral it would have one constituent only.

The name derives from the Latin, lapis, which means stone, and from the Persian, لاژورد lazhward, which means blue.

Contents

Description

A carving in high quality lapis lazuli, showing gold-colored inclusions of . These inclusions are common in lapis and are an important help in identifying the stone. The carving is 8 cm (3 inches) long.
Enlarge
A carving in high quality lapis lazuli, showing gold-colored inclusions of pyrite. These inclusions are common in lapis and are an important help in identifying the stone. The carving is 8 cm (3 inches) long.

The main component of lapis lazuli is lazurite (25 to 40 percent), a feldspathoid silicate mineral composed of sodium, aluminium, silicon, oxygen, sulfur, and chlorine. Most lapis also contains calcite (white), sodalite (blue) and pyrite (yellow). Other possible constituents are augite, diopside, enstatite, mica, hauynite, hornblende and nosean. Lazurite's formula is (Na,Ca)8(AlSiO4)6(S,SO4,Cl)1-2 [1] (http://www.mindat.org/min-2357.html).

Lapis lazuli usually occurs in crystalline limestones as a result of contact metamorphism (see metamorphic rock).

The finest color is intense blue, lightly dusted with small flecks of golden pyrite. There should be no white calcite veins and the pyrite inclusions should be small. Stones that contain too much calcite or pyrite are not as valuable. 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, but these are often a very dark blue with a noticeable grey cast.

Uses

Lapis takes an excellent polish and has been made into jewellery, 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 an oil paint was mostly replaced in the early 19th century by the chemically identical synthetic variety, often called French Ultramarine.

Enhancements

The most common enhancement for lapis lazuli is dyeing (staining), where a stone with white calcite inclusions is stained blue to improve the colour. Other enhancements commonly seen are waxing and resin impregnations, again to improve colour. The colour of stained lapis is unstable and will fade with time.

As with all precious stones, it is a good practice to have any major purchases tested by a reputable gem lab to determine if the stone has been enhanced.

Imitations

Sintered synthetic blue spinel was once used as an imitation of lapis lazuli but is rarely seen today. So-called synthetic lapis lazuli (such as the Gilson product) is more properly termed an imitation, since it does not match exactly the structure and properties of the natural. It is found in various forms, complete with pyrite specks (but all lacking calcite). Various forms of glass and plastic are also commonly seen as imitations.

History

In ancient times, lapis lazuli was known as sapphire, which is the name that we use today for the blue corundum variety sapphire. It appears to have been the sapphire of ancient writers because Pliny refers to sapphirus as a stone sprinkled with specks of gold. A similar reference can be found in the Christian Bible in Job xxviii. 6.

With the ancient Egyptians lapis lazuli was a favourite stone for amulets and ornaments such as scarabs; it was also used by the Assyrians and Babylonians for seals. . Egyptian burial sites dating before 3000 B.C. contained thousands of jewelry items, many of lapis. Powdered lapis was favored by Egyptian ladies as a cosmetic eye shadow.

The ancient royal Sumerian tombs of Ur, located near the Euphrates River in lower Iraq, contained more than 6000 beautifully executed lapis lazuli statuettes of birds, deer, and rodents as well as dishes, beads, and cylinder seals. These carved artifacts undoubtedly came from material mined in Badakhshan in northern Afghanistan. The word lazuli itself originates from the Persian dialect of Badakhshan.

The Romans believed that lapis was a powerful aphrodisiac. In the Middle Ages, it was thought to keep the limbs healthy, and free the soul from error, envy and fear.

It was once believed that lapis had medicinal properties. It was ground down, mixed with milk and applied as a dressing for boils and ulcers.

Many of the blues in painting from medieval Illuminated manuscripts to Renaissance panels were derived from lapis lazuli. Ground to a powder and processed to remove impurities and isolate the component lazurite, it forms the pigment ultramarine. This clear, bright blue, which was one of the few available to painters before the 19th century, cost a princely sum. As tempera painting was superseded by the advent of oil paint in the Renaissance, painters found that the brilliance of ultramarine was greatly diminished when it was ground in oil and this, along with its cost, led to a steady decline in usage. Since the synthetic version of ultramarine was discovered in the 19th century (along with other 19th century blues, such as cobalt blue), production and use of the natural variety has almost ceased, though several pigment companies still produce it and some painters are still attracted to its brilliance and its romantic history.

Metaphysical qualities

As inscribed in the 140th chapter of the Egyptian Book of the Dead, lapis lazuli, in the shape of an eye set in gold, was considered an amulet of great power. On the last day of the month, an offering was made before this symbolic eye, for it was believed that, on that day, the supreme being placed such an image on his head.

Lapis lazuli is said to be associated with self-confidence, truthfulness, openness and inner tranquility. Lapis lazuli is the ancient stone of mental and psychological health, said to promote spiritual healing, mental calmness and strength of will, increased psychic abilities and spiritual growth.

When used during meditation, it is believed to aid in detaching the mind from the physical body and allowing for a deeper and more open state of consciousness. It helps establish a connection with the creative force and in receiving information from other planes of consciousness.

It is said to be a good stone for emotional healing and treatment of disorders of the throat, bone marrow, thymus, and immune system.

Details

Color: blue, mottled with white calcite and brassy pyrite
Habit: compact, massive
Density: 2.7 to 3.0 grams per cubic centimetre
Specific Gravity: 2.4
Hardness: 5 - 5.5
Streak: light blue
Fracture: uneven
Crystal system: none, lapis is a rock. Lazurite, the main constituent, frequently occurs as dodecahedra
Luster: vitreous to greasy
Cleavage: none
Composition: sodium calcium aluminium silicate
Transparency: opaque
Refractive index: 1.5

The variations in composition cause a wide variation in the above values.

Sources

The most important sources are the mines in Badakhshan, northeastern Afghanistan, and those near Ovalle, Chile, where it is usually pale rather than deep blue. Other less important sources are the Lake Baikal region of Russia, Siberia, Angola, Burma, Pakistan, USA (California and Colorado) and Canada.

Poetry

Lapis Lazuli is a poem written by William Butler Yeats. Text available at Readprint.com (http://www.readprint.com/work-1586/William-Butler-Yeats)

External links

fr:Lapis-lazuli nl:Lapis lazuli ja:ラピスラズリ pl:Lazuryt pt:Lapislazuli

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