Encyclopedia > Lapis lazuli

  Article Content

Lapis lazuli

Lapis lazuli is one of the oldest of all gems, with a history of use stretching back 7,000 years. 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 Arabic, azul, which means blue.

A carving in high quality lapis lazuli, showing gold-coloured 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.
Larger version

Its main component is lazurite (25 to 40 percent), a mineral composed of sodium, aluminium, silicon, oxygen and sulphur. Most lapis also contains calcite (white), sodalite[?] (blue) and pyrite (yellow). Other possible constituents are augite[?], diopside[?], enstatite[?], mica, hauynite[?], hornblende and nosean[?]. Its formula is (Na,Ca)8(Al,Si)12(O)24(S)2 FeS- CaCO3.

It 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.

Table of contents

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 is also ground and used to make pigment for oil paint.

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 northern Afghanistan.

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.

The beautiful blues in paintings from the Renaissance are thanks to the blue of lapis lazuli. Ground to a powder it forms the pigment ultramarine. Ultramarine has now been largely superseded by artificial preparations.

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 Colour: 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
Lustre: vitreous to greasy
Cleavage: none
Composition: sodium calcium aluminium silicate
Transparency: opaque
Refractive index: 1.5
The variation in composition causes a wide variation in the above values. Sources The major deposits are found in the West Hindu Kush mountains of Afghanistan. Lapis lazuli is also found in Chile, where the material is heavily mottled with calcite. Other less important sources are the Lake Baikal region of Russia, Siberia, Angola, Burma, Pakistan, USA (California and Colorado) and Canada.

External links http://www.gemstone.org/gem-by-gem/english/lapis
http://www.jewelrymall.com/stones/lapis
http://www.jewelrycentral.com/Target_Lapis
http://www.mineralminers.com/html/lapjlry.stm
http://www.palagems.com/lapis_lazuli_bancroft.htm
http://www.unconventionallapidarist.com/gems/lapis
http://www.afghan-network.net/Culture/lapis-lazuli
http://www.highestoffer.com/lapis



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
Classical mechanics

... law must be used. Newton's second law is insufficient to describe the motion of a particle. In addition, we require a description of F, which is to be obtained by ...