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Amber Author- Ganesh

Amber pendants. The oval pendant is 52 by 32 mm (2 by 1.3 inches)

Amber is the name for fossil resin or tree sap that is appreciated for its colour. It is used for the manufacture of ornamental objects and jewellery. Although not mineralized, it is sometimes considered a gemstone. Most of the world's amber is in the range of 30–90 million years old. Semi-fossilized resin or sub-fossil amber is called copal.The presence of insects in amber was noticed by the Romans and led them to the (correct) theory that at some point, amber had to be in a liquid state to cover the bodies of insects. Hence they gave it the expressive name of suceinum or gum-stone , a name that is still in use today to describe succinic acid as well as succinite , a term given to a particular type of amber by James Dwight Dana (see below under Baltic Amber). The Greek name for amber was ηλεκτρον ( Electron ) and was connected to the Sun God, one of whose titles was Elector or the Awakener .

The modern term electron was coined in 1891 by the Irish physicist George Stoney, using the Greek word for amber (and which was then translated as electr um ) because of its electrostatic properties and whilst analyzing elementary charge for the first time. The ending -on , common for all subatomic particles, was used in analogy to the word ion .

Heating amber will soften it and eventually it will burn, which is why in Germanic languages the word for amber is a literal translation of burn-Stone (In German it is Bernstein , in Dutch it is barnsteen etc.). Heated below 200°C, amber suffers decomposition, yielding an "oil of amber", and leaving a black residue which is known as "amber colophony", or "amber pitch"; when dissolved in oil of turpentine or in linseed oil this forms "amber varnish" or "amber lac". As mentioned above, amber was well known for its electrostatic properties since antiquity (though not identified as such until the concept of electronic charge became clear)

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A mosquito and a fly in this Baltic amber necklace are between 40 and 60 million years old.

Contents

••• 1 Chemistry of amber

••• 2 Amber in geology

••• 3 Amber inclusions

••• 4 Amber locations

o 4.1 Baltic amber

o 4.2 Other locations

••• 5 Amber treatments

••• 6 Amber art and ornament

1.Chemistry of amber

Amber is heterogeneous in composition, but consists of several resinous bodies more or less soluble in alcohol, ether and chloroform, associated with an insoluble bituminous substance. Amber is a macromolecule by free radical polymerization of several precursors in the labdane family, communic acid, cummunol and biformene. These labdanes are diterpenes

(C 20 H32 ) and trienes which means that the organic skeleton has three alkene groups available for polymerization. As amber matures over the years, more polymerization will take place as well as isomerization reactions, crosslinking and cyclization. The average composition of amber leads to the general formula C 10 H16 O.

Amber should be distinguished from copal. Molecular polymerisation caused by pressure and heat transforms the resin firstly into copal and then over time through the evaporation of turpenes it is transformed into amber.Baltic amber is distinguished from the various other ambers from around the world, by the presence within it of succinic acid hence why Baltic amber is otherwise known as succinite.

2.Amber in geology

A bee and a Leaf inside the amber .

Baltic amber or succinite (historically documented as Prussian amber) is found as irregular nodules in a marine glauconitic sand, known as blue earth, occurring in the Lower Oligocene strata of Sambia in Kaliningrad Oblast, where it is now systematically mined. It appears, however, to have been partly derived from yet earlier Tertiary deposits (Eocene); and it occurs also as a derivative mineral in later formations, such as the drift. Relics of an abundant flora occur as inclusions trapped within the amber while the resin was yet fresh, suggesting relations with the flora of Eastern Asia and the southern part of North America. Heinrich Göppert named the common amber-yielding pine of the Baltic forests Pinites succiniter , but as the wood, according to some authorities, does not seem to differ from that of the existing genus it has been also called Pinus succinifera . It is improbable, however, that the production of amber was limited to a single species; and indeed a large number of conifers belonging to different genera are represented in the amber- flora.Amber from the Middle Cretaceous is known from Ellsworth County, Kansas. This approximately 100 million year old amber has inclusions of bacteria and amoebae. They are morphologically very close to Leptothrix, and the modern genera Pontigulasia and Nebela. Morphological stasis is considered to be confirmed.

3.Amber inclusions

An ant trapped in amber

Insect trapped in amber. The amber piece is 10 mm (0.4 inches) long. In the enlarged picture, the insect's antennae are easily seen .

The resin contains, in addition to the beautifully preserved plant-structures, numerous remains of insects, spiders, annelids, frogs, crustaceans and other small organisms which became enveloped while the exudation was fluid. In most cases the organic structure has disappeared, leaving only a cavity, with perhaps a trace of chitin. Even hair and feathers have occasionally been represented among the enclosures. Fragments of wood frequently occur, with the tissues well-preserved by impregnation with the resin; while leaves, flowers and fruits are occasionally found in marvelous perfection. Sometimes the amber retains the form of drops and stalactites, just as it exuded from the ducts and receptacles of the injured trees. It is thought that, in addition to exuding onto the surface of the tree, amber resin also originally flowed into hollow cavities or cracks within trees, thereby leading to the development of large lumps of amber of irregular form. The abnormal development of resin has been called succinosis . Impurities are quite often present, especially when the resin dropped on to the ground, so that the material may be useless except for varnish-making, whence the impure amber is called firniss . Enclosures of pyrites may give a bluish colour to amber. The so-called black amber is only a kind of jet. Bony amber owes its cloudy opacity to minute bubbles in the interior of the resin. A type of amber known as blue amber exists in the Dominican Republic.

4. Amber locations

Baltic amber

Amber has a very wide distribution, extending over a large part of northern Europe and occurring as far east as the Urals.

True amber yields on dry distillation succinic acid, the proportion varying from about 3% to 8%, and being greatest in the pale opaque or bony varieties. The aromatic and irritating fumes emitted by burning amber are mainly due to this acid. True Baltic amber is distinguished by its yield of succinic acid, for many of the other fossil resins which are often termed amber contain either none of it, or only a very small proportion; hence the name succinite proposed by Professor James Dwight Dana, and now commonly used in scientific writings as a specific term for the real Prussian amber. Succinite has a hardness between 2 and 3, which is rather greater than that of many other fossil resins. Its specific gravity varies from 1.05 to 1.10. An effective tool for amber analysis is IR spectroscopy. It enables the distinction between Baltic and non-Baltic amber varieties because of a specific carbonyl absorption and it can also detect the relative age of an amber sample.

Wood resin, the ancient source of amber

Although amber is found along the shores of a large part of the Baltic Sea and the North Sea, the great amber-producing country is the promontory of Sambia, now part of Russia. About 90% of the world's extractable amber is located in the Kaliningrad region of Russia on the Baltic Sea. Pieces of amber torn from the seafloor are cast up by the waves, and collected at ebb-tide. Sometimes the searchers wade into the sea, furnished with nets at the end of long poles, which they drag in the sea-weed containing entangled masses of amber; or they dredge from boats in shallow water and rake up amber from between the boulders. Divers have been employed to collect amber from the deeper waters. Systematic dredging on a large scale was at one time carried on in the Curonian Lagoon by Messrs Stantien and Becker, the great amber merchants of Königsberg.

At the present time extensive mining operations are conducted in quest of amber. The pit amber was formerly dug in open works, but is now also worked by underground galleries. The nodules from the blue earth have to be freed from matrix and divested of their opaque crust, which can be done in revolving barrels containing sand and water. The sea-worn amber has lost its crust, but has often acquired a dull rough surface by rolling in sand.

Since the establishment of the Amber Road, amber (which is also commonly referred to as the "Lithuanian gold") has substantially contributed to Lithuanian economy and culture. Nowadays a great variety of amber jewelry and amberware is offered to foreign tourists in most souvenir shops as distinctive to Lithuania and its cultural heritage. The Amber Museum containing unique specimen of amber has been established in Palanga, near the sea coast.

Other locations

A lesser known source of amber is in the Ukraine, within a marshy forested area on the Volyhn-Polesie border. Due to the shallow depth that this amber is found at it can be extracted with the simplest of tools, and has hence led to an economy of 'amber poaching' under cover of the forest. This Ukrainian amber is much appreciated for its wide range of colours, and was used in the restoration of 'amber room' in the Empress Catherines palace in St Petersberg (see below).

Rolled pieces of amber, usually small but occasionally of very large size, may be picked up on the east coast of England, having probably been washed up from deposits under the North Sea. Cromer is the best-known locality, but it occurs also on other parts of the Norfolk coast, such as Great Yarmouth, as well as Southwold, Aldeburgh and Felixstowe in Suffolk, and as far south as Walton-on-the-Naze in Essex, whilst northwards it is not unknown in Yorkshire. On the other side of the North Sea, amber is found at various localities on the coast of the Netherlands and Denmark. On the shores of the Baltic it occurs not only on the German and Polish coast but in the south of Sweden, in Bornholm and other islands, and in southern Finland. Some of the amber districts of the Baltic and North Sea were known in prehistoric times, and led to early trade with the south of Europe through the Amber Road.

Amber was carried to Olbia on the Black Sea, Massilia (today Marseille) on the Mediterranean, and Adria at the head of the Adriatic; and from these centres it was distributed over the Hellenic world.

Amber and certain similar substances are found to a limited extent at several localities in the United States, as in the green-sand of New Jersey, but they have little or no economic value. Middle Cretaceous amber has also been found in Ellsworth county, Kansas. It has little value for jewelry makers, but is very valuable to biologists. Unfortunately the source of this amber is currently under a manmade lake. A fluorescent amber occurs in the southern state of Chiapas in Mexico, and is used extensively to create eye-catching jewelery. Blue amber is recorded in the Dominican Republic. These Central American ambers are formed from the resins of legume trees (Hymenea) and not conifers.

Indonesia is also a rich source of amber with large fragments being unearthed in both Java and Bali.

5.Amber treatments

The famous Vienna amber factories which use pale amber to manufacture pipes and other smoking tools, apply a specific procedure when working amber: it is turned on the lathe and polished with whitening and water or with rotten stone and oil, the final lustre being given by friction with flannel. During the working a significant electrostatic charge is developed.

Cloudy unpolished amber, artificially illuminated

When gradually heated in an oil-bath, amber becomes soft and flexible. Two pieces of amber may be united by smearing the surfaces with linseed oil, heating them, and then pressing them together while hot. Cloudy amber may be clarified in an oil-bath, as the oil fills the numerous pores to which the turbidity is due. Small fragments, formerly thrown away or used only for varnish, are now utilized on a large scale in the formation of "ambroid" or "pressed amber". The pieces are carefully heated with exclusion of air and then compressed into a uniform mass by intense hydraulic pressure; the softened amber being forced through holes in a metal plate. The product is extensively used for the production of cheap jewelery and articles for smoking. This pressed amber yields brilliant interference colours in polarized light. Amber has often been imitated by other resins like copal and kauri, as well as by celluloid and even glass. True amber is sometimes coloured artificially.

Often amber (particularly with insect inclusions) is counterfeited using a plastic resin similar in appearance. A simple test (performed on the back of the object) consists of touching the object with a heated pin and determining if the resultant odor is of wood resin. If not, the object is counterfeit, although a positive test may not be conclusive owing to a thin coat of real resin. Often counterfeits will have a too perfect pose and position of the trapped insect.

6.Amber art and ornament

Amber was much valued as an ornamental material in very early times. It has been found in Mycenaeantombs; it is known from lake-dwellings in Switzerland, and it occurs with Neolithic remains in Denmark, whilst in England it is found with interments of the bronze age. A remarkably fine cup turned in amber from a bronze-age barrow at Hove is now in the Brighton Museum. Beads of amber occur with Anglo-Saxon relics in the south of England; and up to a comparatively recent period the material was valued as an amulet. It is still believed to possess a certain medicinal virtue.

Unpolished amber stones, in varying hues

Amber is extensively used for beads and other ornaments, and for cigar-holders and the mouth-pieces of pipes. It is regarded by the Turks as specially valuable, inasmuch as it is said to be incapable of transmitting infection as the pipe passes from mouth to mouth. The variety most valued in the East is the pale straw-coloured, slightly cloudy amber. Some of the best qualities are sent to Vienna for the manufacture of smoking appliances.

The Amber Room was a collection of chamber wall panels commissioned in 1701 for the king of Prussia, then given to Tsar Peter the Great. The room was hidden in place from invading Nazi forces in 1941, who upon finding it in the Catherine Palace, disassembled it and moved it to Königsberg. What happened to the room beyond this point is unclear, but it may have been destroyed when the Russians burned the German fortification where it was stored. It is presumed lost. It was re-created in 2003.

Amethyst Author Ganesh

Quartz

General

Category Mineral variety

Chemical formula Silica (silicon dioxide, SiO 2)

Identification

Color purple

6-sided prism ending in 6-sided Crystal habit pyramid (typical)

Crystal system rhombohedral class 32

Twinning Dauphine law, Brazil law and Japan law

Cleavage None

Fracture Conchoidal

Mohs Scale hardness 7 - lower in impure varieties

Luster Vitreous/glossy

Refractive index nω = 1.543 - 1.553 nε = 1.552 - 1.554

Optical Properties Uniaxial (+) (Positive)

Birefringence +0.009 (B-G interval)

Pleochroism None

Streak White

2.65 constant; variable in impure Specific gravity varieties

Melting point 1650 (±75) °C

Solubility H2O insoluble

Diaphaneity Transparent to translucent

Other Characteristics Piezoelectric

Amethyst is a purple variety of quartz often used as an ornament. The name comes from the Greek a ("not") and methustos ("to intoxicate"), a reference to the belief that the stone protected its owner from drunkenness; the ancient Greeks and Romans wore amethyst and made drinking vessels of it in the belief that it would prevent intoxication.

Contents

• 1 Chemistry • 2 Composition • 3 Hue and Tone • 4 History • 5 Alternate terminology • 6 Geographic distribution • 7 Value • 8 Amethyst in folklore and astrology

1.Chemistry

Amethyst is the purple variety of quartz , its chemical formula is SiO 2.

In the 20th century, the color of amethyst was attributed to the presence of manganese . However, since it is capable of being greatly altered and even discharged by heat, the color was believed by some authorities to be from an organic source. Ferric thiocyanate was suggested, and sulfur was said to have been detected in the mineral.

More recent work has shown that amethyst's coloration is due to ferric iron impurities. Further study has shown a complex interplay of iron and aluminium is responsible for the color.

On exposure to heat, amethyst generally becomes yellow , and much of the citrine, cairngorm, or yellow quartz of jewelry is said to be merely "burnt amethyst." Veins of amethystine quartz are apt to lose their color on the exposed outcrop.

Synthetic amethyst is made to imitate the best quality amethyst. Its chemical and physical properties are so similar to that of natural amethyst that it cannot be differentiated with absolute certainty without advanced gemological testing (which is often cost prohibitive). There is one test (which is not 100 percent certain) based on "Brazil law twinning" (a form of quartz twinning where right and left hand quartz structures are combined in a single crystal which can be used to identify synthetic amethyst rather easily. In theory however it is possible to create this material synthetically as well, but this type is not available in large quantities in the market.

2.Composition

Amethyst is composed of an irregular superposition of alternate lamellae of right-handed and left-handed quartz. It has been shown that this structure may be due to mechanical stresses. As a consequence of this composite formation, amethyst is apt to break with a rippled fracture or to show "thumb markings," and the intersection of two sets of curved ripples may produce on the fractured surface a pattern something like that of "engine turning." Some mineralogists, following Sir David Brewster, apply the name of amethyst to all quartz which exhibits this structure, regardless of color.

Because it has a hardness of 7 on the Mohs scale , amethyst is treasured for its use in jewelry.

A polished amethyst gem stone.

3.Hue and Tone

Amethyst occurs in a continuum of primary hues from a light slightly pinkish violet to a deep grape purple. Amethyst may exhibit one or both secondary hues, red and/or blue. The ideal grade is called "Deep Siberian" and has a primary purple hue of around 75 - 80 percent, 15- 20 percent blue and (depending on the light source) red secondary hues.

4.History

Amethyst was used as a gemstone by the ancient Egyptians and was largely employed in antiquity for intaglios. Beads of amethyst are found in Anglo-Saxon graves in England. It is a widely distributed mineral, but fine, clear specimens that are suitable for cutting as ornamental stones are confined to comparatively few localities. Such crystals occur either in the cavities of mineral-veins and in granitic rocks, or as a lining in agate geodes. A huge geode, or "amethyst-grotto," from near Santa Cruz in southern Brazil was exhibited at the Düsseldorf, Germany Exhibition of 1902. Many of the hollow agates of Brazil and Uruguay contain a crop of amethyst crystals in the interior. Much fine amethyst comes from Russia, especially from near Mursinka in the Ekaterinburg district, where it occurs in drusy cavities in granitic rocks. Many localities in India yield amethyst.

Museum-quality piece of Amethyst

5.Alternate terminology

Due to its popularity as a gemstone, several descriptive terms have been coined in the gem trade to describe the varying colors of amethyst. "Rose de France" is usually a pale pinkish lavender or lilac shade (usually the least-sought color). The most prized color is an intense violet with red flashes and is called "Siberian," although gems of this color may occur from several locations other than Siberia , notably Uruguay and Zambia. In more recent times, certain gems (usually of Bolivian origin) that have shown alternate bands of amethyst purple with citrine orange have been given the name ametrine. Purple corundum, or sapphire of amethystine tint, is called Oriental amethyst, but this expression is often applied by jewelers to fine examples of the ordinary amethystine quartz, even when not derived from eastern sources. Professional gemological associations, such as the Gemological Institute of America (GIA) or the American Gemological Society (AGS), discourage the use of the term "Oriental amethyst" to describe any gem, as it may be misleading.

The Second Book of Pseudo-Albertus Magnus, Of the Vertues of Certaine Stones , refers to amethysts by the name Amarictus .

6 carat (1.2 g) pear shape amethyst ring

6.Geographic distribution

Amethyst occurs at many localities in the United States , but these specimens are rarely fine enough for use in jewelry. Among these may be mentioned Amethyst Mountain, Texas; Yellowstone National Park; Delaware County, Pennsylvania; Haywood County, North Carolina; Deer Hill and Stow, Maine. It is found also in the Lake Superior region. Amethyst is relatively common in northwestern Ontario, and in various locations throughout Nova Scotia, but uncommon elsewhere in Canada. Amethyst is produced in abundance from the state of Minas Gerais in Brazil where it occurs in large geodes within volcanic rocks. It is also found and mined in South Korea. The largest opencast amethyst vein in the world is in Maissau, Lower Austria.

7.Value

Traditionally included in the cardinal, or most valuable, gemstones (along with diamond , sapphire, ruby, and emerald), amethyst has lost much of its value due to the discovery of extensive deposits in locations such as Brazil. The highest grade Amethyst (called "Deep Russian") is exceptionally rare and therefore its value is dependent on the demand of collectors when one is found. It is however still orders of magnitude lower than the highest grade sapphires or rubies (Padparadscha Sapphire or "Pigeon Blood" Ruby) which can go for as much as $50,000 or more per carat.

Amethyst such as the "Russian" quality (bluish purple key color) and such as material recently found in Georgia since 2005 (with some of the stones showing both blue hue and red flashes) and of which its top material is considered of the best quality presently available still command prices of not more than $50 per carat.

8.Amethyst in folklore and astrology

Amethyst is the birthstone associated with February. It is also associated with the astrological signs of Pisces, Aries (especially the violet and purple variety), Aquarius, and Sagittarius. It is a symbol of heavenly understanding, and of the pioneer in thought and action on the philosophical, religious, spiritual, and material planes. Ranking members of the Roman Catholic Church traditionally wear rings set with a large amethyst as part of their office. The Greek word "amethystos" (αµέθυστος) basically can be translated as "not drunken." Amethyst was considered to be a strong antidote against drunkenness, which is why wine goblets were often carved from it. Supposedly, when a drunken Dionysus was pursuing a maiden called Amethystos, who refused his affections, she prayed to the gods to remain chaste. The goddess Artemis granted the prayer, transforming her into a white stone; humbled by Amethystos' desire to remain chaste, Dionysus poured wine over the stone she had become as an offering, dyeing the crystals purple.

Variants of the story include that Dionysus, the god of intoxication, had been insulted by a mortal and swore revenge on the next mortal who crossed his path, creating fierce tigers to carry out his wish; the mortal turned out to be a beautiful young woman, Amethystos, who was on her way to pay tribute to Artemis. Her life is spared by Artemis, who transforms the maiden into a statue of pure crystalline quartz to protect her from the brutal claws. Dionysus wept tears of wine in remorse for his action at the sight of the beautiful statue. The god's tears stained the quartz purple. Another variation involves the goddess Rhea presenting Dionysus with the amethyst stone to preserve the winedrinker's sanity. Aquamarine Author Ganesh

Aquamarine

General

Category beryl variety

Chemical formula Be 3Al 2Si 6O18 Identification

transparent (or can be tra nslucent if Color included), greenish blue to blue green, typically light in tone

Crystal system hexagonal

very difficult in one direction, almost Cleavage never seen

Fracture conchoidal

Mohs Scale hardness 7.5 - 8

Luster vitreous to resinous

Polish luster vitreous

Refractive index 1.577 - 1.583 (+/- .017)

Optical Properties Double refractive, uniaxial negative

Birefringence .005 - .009

Dispersion .014

weak to moderate, blue and greenish blue; or different tones of blu e with lighter Pleochroism tones associated with the optic axis direction

Ultraviolet fluorescence inert

indistinct lines at 537 and 456nm. Absorption spectra Depending on the depth of color, there is a strong line at 427nm.

Specific gravity 2.72 (+.18, -.05)

Aquamarine (Lat. aqua marinā , "water of the sea") is a gemstone-quality transparent variety of beryl, having a delicate blue or turquoise color, suggestive of the tint of seawater. It's closely related to the gem emerald. Colors vary and yellow beryl (heliodor), rose pink beryl (morganite), and white beryl (goshenite) are known.

Contents

• 1 Composition • 2 Locations of deposits • 3 Culture and historical/mythical usage

1.Composition

Aquamarine is a beryl with a hexagonal crystal structure and a chemical formula of

Be 3Al 2Si 6O18 , a beryllium aluminium silicate mineral. It has a specific gravity of 2.68 to 2.74 and a Mohs hardness of from 7.5 to 8. Aquamarine typically is on the low end of the specific gravity range, normally at less than 2.7. The pink variety exhibits a high specific gravity of around 2.8. Refractive indices range around 1.57 to 1.58.

2.Locations of deposits

It occurs at most localities which yield ordinary beryl, some of the finest coming from Russia. The gem-gravel placer deposits of Sri Lanka contain aquamarine. Clear yellow beryl, such as occurs in Brazil, is sometimes called aquamarine chrysolite. When corundum presents the bluish tint of typical aquamarine, it is often termed Oriental aquamarine.

In the United States, aquamarines can be found at the summit of Mt. Antero in the Sawatch Range in central Colorado. In Brazil, there are mines in the states of Minas Gerais, Espírito Santo and Bahia. Zambia, Madagascar, Malawi, Tanzania and Kenya also produce aquamarine. The biggest aquamarine ever mined was found at the city of Marambaia, Minas Gerais, Brazil, in 1910. It weighed over 110 kg, and its dimensions were 48.5 cm long and 42 cm in diameter. Aquamarine is the official state gem of Colorado.

3.Culture and historical/mythical usage

• Aquamarine (along with Bloodstone) is the birthstone associated with March. It is also the gemstone for the 19th Anniversary. • People in the Middle Ages thought that aquamarine could magically overcome the effects of poison. • Ancient sailors traveled with aquamarine crystals, believing that it would ensure a safe passage, and guarantee a safe return; they often slept with the stones under their pillow to ensure sound sleep. They believed the siren’s (mermaid) fish-like lower body was made of aquamarine.

Three Beryl Crystals - Aquamarine rough crystal in the center Chrysoberyl Author Ganesh

Chrysoberyl

General Category Mineral

Chemical formula Beryllium aluminium oxide, BeAl 2O4 Identification Various shades of green and yellow; Color brownish, reddish; rarely, blue slender prisms and tabular form, Crystal habit dimensions are thin in one direction. Crystal system Orthorhombic 2/m2/m2/m Contact and penetration twins Twinning common, often repeated forming rosette structures Cleavage [110] Distinct, [010] Imperfect Fracture Conchoidal to uneven Mohs Scale hardness 8.5 Luster Vitreous Biaxial (+) nα=1.745 nβ=1.748 Refractive index nγ=1.754 Pleochroism Strong in alexandrite Streak White Specific gravity 3.5 - 3.84 Major varieties Alexandrite Color change; green to red Cymophane Chatoyant

The mineral or gemstone chrysoberyl , not to be confused with beryl, is an aluminate of beryllium with the formula BeAl 2O4. The name chrysoberyl is derived from the Greek words chrysos and beryllos , meaning "golden" and "gem crystal". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones. Chrysoberyl is the third hardest naturally occurring gemstone and lies between corundum and topaz on the hardness scale. Chrysoberyl is a mineral consisting of ordinary colorless or yellow transparent chrysoberyl, cymophane (chrysoberyl cat's eye), and alexandrite.

An interesting feature of uncut crystals of chyrsoberyl are the cyclic twins called trillings . These twinned crystals have a hexagonal appearance, but are the result of a triplet of twins with each "twin" taking up 120 degrees of the cyclic trilling. There are three main varieties of chrysoberyl; ordinary yellow chrysoberyl, cat's eye or cymophane, and alexandrite. Although yellow chrysoberyl was referred to as chrysolite during the Victorian and Edwardian eras, that name is no longer used in the gemological nomenclature.

Ordinary chrysoberyl is a yellowish-green, transparent to translucent chrysoberyl and has often been referred to in the literature as chrysolite due to the common olive color of many of its gems, but that name is no longer used in the gemological nomenclature. When the mineral exhibits good pale green to yellow color and is transparent, then it is used as a gemstone. Alexandrite, a strongly pleochroic (trichroic) gem, will exhibit emerald green, red and orange-yellow colors and tend to change color in artificial light compared to daylight. The color change from red to green is due to strong absorption of light in the yellow and blue portions of the spectrum. Typically, alexandrite has an emerald green color in daylight but exhibit a raspberry red color in incandescent light.

Cymophane is popularly known as cat's eye. This variety exhibits pleasing chatoyant or opalescence that reminds one of an eye of a cat. When cut to produce a cabochon, the mineral forms a light-green specimen with a silky band of light extending across the surface of the stone.

Contents

• 1 Occurrence • 2 Chrysoberyl • 3 Alexandrite • 4 Cymophane

1.Occurrence

Chrysoberyl was formed as a result of pegmatitic processes that occurred at least 250 million years ago. High temperatures and pressures from the outer layers of the earth's mantle forced molten magma towards the surface. As the main magma body cooled, water originally present in low concentrations became more concentrated in the molten rock because it could not be incorporated into the crystallization of the localized minerals. Consequently, the remaining portion of the molten magma was water rich. It was also rich in rare elements and silica that still had not solidified. When this water-rich magma was expelled in the final stages of the crystallization, it solidified in cracks and crevasses to form a pegmatite.

If the pegmatite magma was rich in beryllium , crystals of beryl and chrysoberyl could form but for alexandrite to form, some chromium would also have had to be present. Since beryllium and chromium are extremely rare elements in rocks, this is the only known process which could have concentrated these unusual elements in an environment where crystallization could occur.

The high water content of the magma made it possible for the crystals to grow quickly, so pegmatite crystals are often quite large and this is of course important for gem specimens. Chrysoberyl is always accompanied by quartz. It occurs in granite pegmatites and mica schists and in contact with metamorphic deposits of dolomitic marble. It is also recovered from river sands and gravels in alluvial deposits with corundum, spinel, garnet and tourmaline.

Chrysoberyl has high enough specific gravity that it will concentrate with black sands in active or paleoplacer stream deposits and concentrate with other relatively heavy minerals such as cassiterite , diamond , corundum, topaz and garnet. When found in placers, it will have rounded edges instead of sharp, wedge-shape forms. Much of the chrysoberyl mined in Brazil and Sri Lanka is recovered from placers as the host rocks have been intensely weathered and eroded.

Chrysoberyl deposits can be divided into three types, excluding rare dolomitic hosts. These include chrysoberyl in pegmatites intruded into ultramafic rocks, chrysoberyl hosted by pegmatites intruded into aluminous rocks, and chrysoberyl found as a primary mineral in REE-pegmatites.

There have been very few research projects on the genesis of chrysoberyl due to its rarity in primary host rocks since most chrysoberyl is recovered from placers. However, it may be hypothesized that in order to produce chrysoberyl, metamorphic overprint of some beryllium- and aluminum-rich pegmatites may be necessary.

2. Chrysoberyl

Yellow chrysoberyl gemstone featuring oval step cut.

Chrysoberyl was discovered in 1789 and described and named by Abraham Gottlob Werner , in 1790. Werner worked at the Freiberg School of Mining from 1790-1793 and was well known as one of the most outstanding geologists of his time. He is best known today as the loser in the battle of the Neptunists and Vulcanists that raged in the 1780s.

Chrysoberyl is normally yellow, yellow-green, or brownish with its color being caused by the presence of iron. Spectroscopic analysis will usually reveal a strong band where the violet takes over from the blue. As the color darkens from bright yellowish-green to golden-yellow to brown, this band increases in strength. When the stone has a strong color, two additional bands can be seen in the green-blue. The most common inclusions are liquid-filled cavities containing three-phase inclusions. Stepped twin planes may be apparent in some cases. Some very rare minty bluish-green chrysoberyls from Tanzania owe their color to the presence of Vanadium.

Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones. Members of the beryl group include emerald, aquamarine, and morganite while members of the chrysoberyl group include chrysoberyl, cymaphane (cat's eye) and alexandrite. Beryl is a silicate and chrysoberyl is an oxide and although both beryl and chrysoberyl contain beryllium, they are separate gemstone species unrelated in any other way. Because of the confusion between chrysoberyl and beryl, chrysoberyl is relatively unknown in its own right and the alexandrite variety is much more widely recognized. The only well-known natural gemstones harder than chrysoberyl are corundum and diamond.

3.Alexandrite

Alexandrite step cut cushion, 26.75 cts. Alexandrites this large are extremely rare.

The alexandrite variety displays a color change ( alexandrite effect ) dependent upon light, along with strong pleochroism . Alexandrite results from small scale replacement of aluminium by chromium oxide, which is responsible for alexandrite's characteristic green to red color change. Alexandrite from the Ural Mountains in Russia is green by daylight and red by incandescent light. Other varieties of alexandrite may be yellowish or pink in daylight and a columbine or raspberry red by incandescent light. The optimum or "ideal" color change would be fine emerald green to fine purplish red, but this is exceedingly rare. Because of their rarity and the color change capability, "ideal" alexandrite gems are some of the most expensive in the world.

According to a widely popular but controversial story, alexandrite was discovered by the Finnish mineralogist Nils Gustaf Nordenskiöld , (1792 -1866) on the tsarevitch Alexander's sixteenth birthday on April 17, 1834 and named alexandrite in honor of the future Tsar Alexander II of Russia. Sometimes, Nils Gustaf Nordenskiöld is confused with his son, Adolf Erik Nordenskjöld (1832–1901), also a famous Finnish geologist, mineralogist and arctic explorer who accompanied his father to the Ural Mountains to study the iron and copper mines at Tagilsk in 1853. However, Adolf Erik Nordenskjöld was only two years old when Alexandrite was discovered and only ten years old when a description of the stone was published under the name of Alexandrite for the first time.

Although it was Nordenskjold who discovered alexandrite, he could not possibly have discovered and named it on Alexander's birthday. Nordensljold's initial discovery occurred as a result of an examination of a newly found mineral sample he had received from Perovskii, which he identified as emerald at first. After the discovery of emeralds in the roots of an upturned tree, the first emerald mine had been opened in 1831, not long before Nordensjold had received this particular sample.

Confused with the high hardness however, he decided to continue his examinations. Later that evening, while looking at the specimen under candlelight, he was surprised to see that the color of the stone had changed to raspberry-red instead of green. Later, he confirmed the discovery of a new variety of chrysoberyl, and suggested the name "diaphanite"(from the Greek "di" two and "aphanes", unseen or "phan", to appear, or show).

The name of the first person to actually find this stone has been lost in the mists of time. However, the first person to bring it to public attention, and ensure that it would be forever associated with the Imperial family was Count Lev Alekseevich Perovskii (1792- 1856.)

The finest alexandrites were found in the Ural Mountains, the largest cut stones being in the 30 carat (6 g) range, though many fine examples have been discovered in Sri Lanka (up to 65 cts.), India ( Andhra Pradesh), Brazil, Myanmar, and especially Zimbabwe (small stones usually under 1 carat (200 mg) but with intense color change). Overall, stones from any locale over 5 carats (1 g) would be considered extremely rare, especially gems with fine color change. Alexandrite is both hard and tough, making it very well suited to wear in jewelry.

The gem has given rise to the adjective "alexandritic", meaning any transparent gem or material which shows a noted change in color between natural and incandescent light. Some other gem varieties of which alexandritic specimens have been found include sapphire , garnet , and spinel. Some gemstones described as lab-grown (synthetic) alexandrite are actually corundum laced with trace elements (e.g., vanadium ) or color-change spinel and are not actually chrysoberyl. As a result, they would be more accurately described as simulated alexandrite rather than synthetic but are often called Czochralski Alexandrite after the process that grows the crystals. Synthetic alexandrite is used as an active laser medium . Alexandrite laser crystals tend to be round, with a pale brown tint. Genuine alexandrite is one of the most expensive gemstones available commercially, with the stronger color changes being more highly valued. The following are average retail prices for alexandrite in December 2004 from The International Gem Society

Faceted (Alexandrite) 0.5 to 1 carat 1 carat plus Top Red/Green $5,000 to $15,000/ct to $100,000/ct Medium Red/Green $3,000 to $9,000/ct to 60,000/ct Slight Red/Green $100 to $2,500/ct to $6,000/ct Other colors $1,100 to $8,000/ct to $10,000/ct Cabochon (Alexandrite) 0.5 to 1 carat 1 carat plus Strong red/green $500 to $2,500/ct to $30,000/ct Cabochon (Cat's Eye) 0.5 to 1 carat 1 carat plus Strong red/green $1,500 to $5,000 N/A

4.Cymophane

Fine color Cymophane with a sharp and centered eye.

Translucent yellowish chatoyant chyrsoberyl is called cymophane or cat's eye . Cymophane has its derivation also from the Greek words meaning 'wave' and 'appearance', in reference to the chatoyancy sometimes exhibited. In this variety, microscopic tubelike cavities or needlelike inclusions of rutile occur in an orientation parallel to the c-axis producing a chatoyant effect visible as a single ray of light passing across the crystal. This effect is best seen in gemstones cut in cabochon form perpendicular to the c-axis. The color in yellow chrysoberyl is due to Fe 3+ impurities.

Although other minerals such as tourmaline , scapolite , corundum, spinel and quartz can form "cat's eye" stones similar in appearance to cymophane, the jewelry industry designates these stones as "quartz cat's eyes", or "ruby cat's eyes" and only chrysoberyl can be referred to as "cat's eye" with no other designation.

Gems lacking the silky inclusions required to produce the cat's eye effect is usually faceted. An alexandrite cat's eye is a chrysoberyl cat's eye that changes color. "Milk and honey" is a term commonly used to describe the color of the best cat's eyes. The effect refers to the sharp milky ray of white light normally crossing the cabochon as a center line along its length and overlying the honey colored background. The honey color is considered to be top by many gemologists but the lemon yellow colors are also popular and attractive. Cat's eye material is found as a small percentage of the overall chrysoberyl production wherever chrysoberyl is found.

Cat's eye really became popular by the end of the 19th century when the Duke of Connaught gave a ring with a cat's eye as an engagement token, this was sufficient to make the stone more popular and increase its value greatly. Up to that time cat's eye had predominantly been present in gem and mineral collections. The increased demand in its turn created an intensified search for it in Ceylon . Early 20th century prices could go up as high as $ 8000 for a cut stone.

Diamond Author ganesh

Diamond

A scattering of round-brilliant cut diamonds shows off the many reflecting facets.

General

Category Native Minerals

Chemical formula C

Identification

Molecular Weight 12.01 u

Typically yellow, brown or gray to colorless. Color Less often in blue, green, black, translucent white, pink, violet, orange, purple and red.

Crystal habit Octahedral

Crystal system Isometric-Hexoctahedral (Cubic)

Cleavage 111 (perfect in four directions)

Fracture Conchoidal - step like

Mohs Scale hardness 10

Luster Adamantine

Polish luster Adamantine

Refractive index 2.4175–2.4178

Optical Properties Singly Refractive

Birefringence None

Dispersion .044

Pleochroism none

colorless to yellowish stones - inert to strong Ultraviolet fluorescence in long wave, and typically blue. Weaker in short wave.

In pale yellow stones a 415.5 nm line is typical. Irradiated and annealed diamonds often show Absorption spectra a line around 594 nm when cooled to low temperatures.

Streak White

Specific gravity 3.52 (+/- .01)

Density 3.5-3.53

Diaphaneity Transparent to subtransparent to translucent

Diamond is an allotrope of carbon . It is the hardest known natural material and the third- hardest known material after aggregated diamond nanorods and ultrahard fullerite. Its hardness and high dispersion of light make it useful for industrial applications and jewelry.

Diamonds are specifically renowned as a material with superlative physical qualities; they make excellent abrasives because they can be scratched only by other diamonds, Borazon , ultrahard fullerite, or aggregated diamond nanorods, which also means they hold a polish extremely well and retain their lustre. Approximately 130 million carats (26,000 kg) are mined annually, with a total value of nearly USD $9 billion, and about 100,000 kg (220,000 lb) are synthesized annually.

The name diamond derives from the ancient Greek adamas (αδάµας; “invincible”). They have been treasured as gemstones since their use as religious icons in ancient India and usage in engraving tools also dates to early human history. Popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns. They are commonly judged by the “four Cs”: carat , clarity , color , and cut .

Roughly 49% of diamonds originate from central and southern Africa , although significant sources of the mineral have been discovered in Canada , India, Russia, Brazil, and Australia. They are mined from kimberlite and lamproite volcanic pipes, which brought to the surface the diamond crystals from deep in the Earth where the high pressure and temperature enables the formation of the crystals. The mining and distribution of natural diamonds are subjects of frequent controversy such as with concerns over the sale of conflict diamonds (aka blood diamonds ) by African paramilitary groups.

Contents

• 1 Material properties o 1.1 Hardness o 1.2 Electrical conductivity o 1.3 Toughness o 1.4 Color o 1.5 Identification • 2 Natural history o 2.1 Formation
2.1.1 Diamonds formed in cratons
2.1.2 Diamonds and meteorite impact craters
2.1.3 Extraterrestrial diamonds o 2.2 Surfacing • 3 History and gemological characteristics • 4 The diamond industry o 4.1 Gem diamond industry o 4.2 Industrial diamond industry o 4.3 Diamond supply chain
4.3.1 Mining, sources and production
4.3.2 "Blood" diamonds
4.3.3 Distribution • 5 United States

1.Material properties

A diamond is a transparent crystal of tetrahedrally bonded carbon atoms and crystallizes into the face centered cubic diamond lattice structure. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness, its high dispersion index, and extremely high thermal conductivity (900 – 2320 W/m K), with a melting point of 3820 K (3547 °C / 6420 °F) and a boiling point of 5100 K (4827 °C / 8720 °F). Naturally occurring diamonds have a density ranging from 3.15 to 3.53 g/cm³, with very pure diamond typically extremely close to 3.52 g/cm³.

Hardness

Diamond is the hardest natural material known to man; hardness is defined as resistance to scratching. Diamond has a hardness of 10 (hardest) on Mohs scale of mineral hardness . Diamond's hardness has been known since antiquity, and is the source of its name.

The hardest diamonds in the world are from the New England area in New South Wales , Australia. These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds. Their hardness is considered to be a product of the crystal growth form, which is single stage growth crystal. Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice, all of which affect their hardness.

The hardness of diamonds contributes to its suitability as a gemstone . Because it can only be scratched by other diamonds, it maintains its polish extremely well. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in an engagement ring or wedding ring, which are often worn every day.

Industrial use of diamonds has historically been associated with their hardness; this property makes diamond the ideal material for cutting and grinding tools. As the hardest known naturally-occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. However, diamond is a poor choice for machining ferrous alloys at high speeds. At the high temperatures created by high speed machining, carbon is soluble in iron, leading to greatly increased wear on diamond tools as compared to other alternatives. Common industrial adaptations of this ability include diamond-tipped drill bits and saws, or use of diamond powder as an abrasive . Industrial-grade diamonds are either unsuitable for use as gems or synthetically produced, which lowers their value and makes their use economically feasible.

Electrical conductivity

Other specialized applications also exist or are being developed, including use as semiconductors : some blue diamonds are natural semiconductors, in contrast to most other diamonds, which are excellent electrical insulators .

Toughness

Toughness relates to a material's ability to resist breakage from forceful impact. The toughness of natural diamond has been measured as 3.4 MN m -3/2 , which is good compared to other gemstones, but poor compared to most engineering materials. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamond is therefore more fragile in some orientations than others.

Color

Diamonds can occur in nearly any color, though yellow and brown are by far the most common. "Black" diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities replace a carbon atom in the crystal lattice , known as a carbon flaw . The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present. The Gemological Institute of America (GIA) classifies low saturation yellow and brown diamonds as diamonds in the normal color range , and applies a grading scale from 'D' (colorless) to 'Z' (light yellow).

A blue diamond recently fetched nearly $8 million. The blue hue was a result of trace amounts of boron in the stone's crystal structure.

Identification

Diamonds can be identified via their high thermal conductivity. Their high refractive index is also indicative, but other materials have similar refractivity. Diamonds do cut glass, but other materials above glass on Mohs scale such as quartz do also. Diamonds easily scratch other diamonds, but this damages both diamonds.

2.Natural history

Formation

The formation of natural diamond requires very specific conditions. Diamond formation requires exposure of carbon-bearing materials to high pressure , ranging approximately between 45 and 60 kilobars, but at a comparatively low temperature range between approximately 1652–2372 °F (900–1300 °C). These conditions are known to be met in two places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike.

Diamonds formed in cratons

The conditions for diamond formation to happen in the lithospheric mantle occur at considerable depth corresponding to the aforementioned requirements of temperature and pressure.

These depths are estimated to be in between 140–190 kilometers (90–120 miles) though occasionally diamonds have crystallized at depths of 300-400 km (180-250 miles) as well. The rate at which temperature changes with increasing depth into the Earth varies greatly in different parts of the Earth. In particular, under oceanic plates the temperature rises more quickly with depth, beyond the range required for diamond formation at the depth required. The correct combination of temperature and pressure is only found in the thick, ancient, and stable parts of continental plates where regions of lithosphere known as cratons exist. Long residence in the cratonic lithosphere allows diamond crystals to grow larger.

The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral. Its lustrous faces also indicate that this crystal is from a primary deposit.

Through studies of carbon isotope ratios (similar to the methodology used in carbon dating , except with the stable isotopes C-12 and C-13), it has been shown that the carbon found in diamonds comes from both inorganic and organic sources. Some diamonds, known as harzburgitic , are formed from inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogitic diamonds contain organic carbon from organic detritus that has been pushed down from the surface of the Earth's crust through subduction (see plate tectonics) before transforming into diamond. These two different source carbons have measurably different 13 C: 12 C ratios. Diamonds that have come to the Earth's surface are generally very old, ranging from under 1 billion to 3.3 billion years old.

Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles or maccles . As diamond's crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cube, octahedron, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron. The crystals can have rounded off and unexpressive edges and can be elongated. Sometimes they are found grown together or form double "twinned" crystals grown together at the surfaces of the octahedron. These different shapes and habits of the diamonds result from differing external circumstances. Diamonds (especially those with rounded crystal faces) are commonly found coated in nyf , an opaque gum-like skin.

Diamonds and meteorite impact craters

Diamonds can also form in other natural high-pressure events. Very small diamonds, known as microdiamonds or nanodiamonds , have been found in meteorite impact craters. Such impact events create shock zones of high pressure and temperature suitable for diamond formation. Impact-type microdiamonds can be used as one indicator of ancient impact craters.

Extraterrestrial diamonds

Not all diamonds found on earth originated here. A type of diamond called carbonado diamond that is found in South America and Africa was deposited there via an asteroid impact (not formed from the impact) about 3 billion years ago. These diamonds formed in the intrastellar environment.

Presolar grains in many meteorites found on earth contain nanodiamonds of extraterrestrial origin, probably formed in supernovas .

White dwarf stars have been described as having a carbon core and were hyped in a 2004 news headline as diamond.

Surfacing

Schematic diagram of a volcanic pipe

Diamond-bearing rock is brought close to the surface through deep-origin volcanic eruptions. The magma for such a volcano must originate at a depth where diamonds can be formed, 150 km (90 miles) deep or more (three times or more the depth of source magma for most volcanoes); this is a relatively rare occurrence. These typically small surface volcanic craters extend downward in formations known as volcanic pipes. The pipes contain material that was transported toward the surface by volcanic action, but was not ejected before the volcanic activity ceased. During eruption these pipes are open to the surface, resulting in open circulation; many xenoliths of surface rock and even wood and/or fossils are found in volcanic pipes. Diamond-bearing volcanic pipes are closely related to the oldest, coolest regions of continental crust (cratons). This is because cratons are very thick, and their lithospheric mantle extends to great enough depth that diamonds are stable. Not all pipes contain diamonds, and even fewer contain enough diamonds to make mining economically viable.

The magma in volcanic pipes is usually one of two characteristic types, which cool into igneous rock known as either kimberlite or lamproite. The magma itself does not contain diamond; instead, it acts as an elevator that carries deep-formed rocks (xenoliths), minerals (xenocrysts), and fluids upward.

These rocks are characteristically rich in magnesium-bearing olivine, pyroxene, and amphibole minerals which are often altered to serpentine by heat and fluids during and after eruption. Certain indicator minerals typically occur within diamondiferous kimberlites and are used as mineralogic tracers by prospectors, who follow the indicator trail back to the volcanic pipe which may contain diamonds. These minerals are rich in chromium (Cr) or titanium (Ti), elements which impart bright colors to the minerals. The most common indicator minerals are chromian garnets (usually bright red Cr-pyrope, and occasionally green ugrandite-series garnets), eclogitic garnets, orange Ti-pyrope, red high-Cr spinels, dark chromite, bright green Cr-diopside, glassy green olivine, black picroilmenite, and magnetite. Kimberlite deposits are known as blue ground for the deeper serpentinized part of the deposits, or as yellow ground for the near surface smectite clay and carbonate weathered and oxidized portion.

Once diamonds have been transported to the surface by magma in a volcanic pipe, they may erode out and be distributed over a large area. A volcanic pipe containing diamonds is known as a primary source of diamonds. Secondary sources of diamonds include all areas where a significant number of diamonds, eroded out of their kimberlite or lamproite matrix, accumulate because of water or wind action. These include alluvial deposits and deposits along existing and ancient shorelines, where loose diamonds tend to accumulate because of their approximate size and density. Diamonds have also rarely been found in deposits left behind by glaciers (notably in Wisconsin and Indiana); however, in contrast to alluvial deposits, glacial deposits are not known to be of significant concentration and are therefore not viable commercial sources of diamond.

3.History and gemological characteristics

Diamonds are thought to have been first recognized and mined in India ( Golconda being one of them), where significant alluvial deposits of the stone could then be found along the rivers Penner, Krishna and Godavari. Diamonds have been known in India for at least 3000 years but most likely 6000 years. The most familiar usage of diamonds today is as gemstones used for adornment a usage which dates back into antiquity. The dispersion of white light into spectral colors, is the primary gemological characteristic of gem diamonds. In the twentieth century, experts in the field of gemology have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem. Four characteristics, known informally as the four Cs , are now commonly used as the basic descriptors of diamonds: these are carat , cut , color , and clarity .

4.The diamond industry

A round brilliant cut diamond set in a ring

The diamond industry can be broadly separated into two basically distinct categories: one dealing with gem-grade diamonds and another for industrial-grade diamonds. While a large trade in both types of diamonds exists, the two markets act in dramatically different ways.

Gem diamond industry

A large trade in gem -grade diamonds exists. Unlike precious metals such as gold or platinum, gem diamonds do not trade as a commodity: there is a substantial mark-up in the sale of diamonds, and there is not a very active market for resale of diamonds. One hallmark of the trade in gem-quality diamonds is its remarkable concentration: wholesale trade and diamond cutting is limited to a few locations. 92% of diamond pieces cut in 2003 were in Surat, Gujarat, India. Other important centers of diamond cutting and trading are Antwerp, London, New York, Tel Aviv, Amsterdam. A single company—De Beers—controls a significant proportion of the trade in diamonds. They are based in Johannesburg, South Africa and London, England.

The production and distribution of diamonds is largely consolidated in the hands of a few key players, and concentrated in traditional diamond trading centers. The most important being Antwerp , where 80% of all rough diamonds, 50% of all cut diamonds and more than 50% of all rough, cut and industrial diamonds combined are handled. This makes Antwerp the de facto 'world diamond capital'. New York , however, along with the rest of the United States, is where almost 80% of the world's diamonds are sold, including at auction. Also, the largest and most unusually shaped rough diamonds end up in New York. The De Beers company, as the world's largest diamond miner holds a clearly dominant position in the industry, and has done so since soon after its founding in 1888 by the British imperialist Cecil Rhodes. De Beers owns or controls a significant portion of the world's rough diamond production facilities (mines) and distribution channels for gem-quality diamonds. The company and its subsidiaries own mines that produce some 40 percent of annual world diamond production. At one time it was thought over 80 percent of the world's rough diamonds passed through the Diamond Trading Company (DTC, a subsidiary of De Beers) in London, but presently the figure is estimated at less than 50 percent.

The De Beers diamond advertising campaign is acknowledged as one of the most successful and innovative campaigns in history. N. W. Ayer & Son , the advertising firm retained by De Beers in the mid-20th century, succeeded in reviving the American diamond market and opened up new markets, even in countries where no diamond tradition had existed before. N.W. Ayer's multifaceted marketing campaign included product placement, advertising the diamond itself rather than the De Beers brand, and building associations with celebrities and royalty. This coordinated campaign has lasted decades and continues today; it is perhaps best captured by the slogan "a diamond is forever".

Further down the supply chain, members of The World Federation of Diamond Bourses (WFDB) act as a medium for wholesale diamond exchange, trading both polished and rough diamonds. The WFDB consists of independent diamond bourses in major cutting centres such as Tel Aviv, Antwerp, Johannesburg and other cities across the USA, Europe and Asia.

In 2000, the WFDB and The International Diamond Manufacturers Association established the World Diamond Council to prevent the trading of diamonds used to fund war and inhumane acts.

WFDB's additional activities also include sponsoring the World Diamond Congress every two years, as well as the establishment of the International Diamond Council (IDC) to oversee diamond grading.

Industrial diamond industry

The market for industrial-grade diamonds operates much differently from its gem-grade counterpart. Industrial diamonds are valued mostly for their hardness and heat conductivity, making many of the gemological characteristics of diamond, including clarity and color, mostly irrelevant. This helps explain why 80% of mined diamonds (equal to about 100 million carats or 20,000 kg annually), unsuitable for use as gemstones and known as bort , are destined for industrial use. In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; another 3 billion carats (600 metric tons) of synthetic diamond is produced annually for industrial use.

The dominant industrial use of diamond is in cutting, drilling, grinding, and polishing. Most uses of diamonds in these technologies do not require large diamonds; in fact, most diamonds that are gem-quality except for their small size, can find an industrial use. Diamonds are embedded in drill tips or saw blades, or ground into a powder for use in grinding and polishing applications. Specialized applications include use in laboratories as containment for high pressure experiments (see diamond anvil ), high-performance bearings, and limited use in specialized windows.

With the continuing advances being made in the production of synthetic diamonds, future applications are beginning to become feasible. Garnering much excitement is the possible use of diamond as a semiconductor suitable to build microchips from, or the use of diamond as a heat sink in electronics.

Diamond supply chain

The diamond supply chain is controlled by a limited number of powerful businesses, and is also highly concentrated in a small number of locations around the world.

Mining, sources and production

Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care has to be taken in order to prevent larger diamonds from being destroyed in this process and subsequently the particles are sorted by density. Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence , after which the final sorting steps are done by hand. Before the use of X- rays became commonplace, the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.

Historically diamonds were known to be found only in alluvial deposits in southern India . India led the world in diamond production from the time of their discovery in approximately the 9th century BCE to the mid-18th century AD, but the commercial potential of these sources had been exhausted by the late 18th century and at that time India was eclipsed by Brazil where the first non-Indian diamonds were found in 1725.

Diamond production of primary deposits (kimberlites and lamproites) only started in the 1870's after the discovery of the Diamond fields in South Africa. Production has increased over time and now an accumulated total of 4.5 billion carats have been mined since that date. Interestingly 20% of that amount has been mined in the last 5 years alone and during the last ten years 9 new mines have started production while 4 more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.

While no commercial diamond production exists in the US , Arkansas and Colorado are the only states to have a verifiable source of diamonds.

Today, most commercially viable diamond deposits are in Russia , Botswana , Australia and the Democratic Republic of Congo. In 2005, Russia produced almost one-fifth of the global diamond output, reports the British Geological Survey. Australia boasts the richest diamondiferous pipe with production reaching peak levels of 42 metric tons (41 LT/46 ST) per year in the 1990's.

There are also commercial deposits being actively mined in the Northwest Territories of Canada, Siberia (mostly in Yakutia territory, for example Mir pipe and Udachnaya pipe), Brazil, and in Northern and Western Australia. Diamond prospectors continue to search the globe for diamond-bearing kimberlite and lamproite pipes.

"Blood" diamonds

In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines , using proceeds from diamond sales to finance their operations. Diamonds sold through this process are known as conflict diamonds or blood diamonds . Major diamond trading corporations continue to fund and fuel these conflicts by doing business with armed groups. In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central Africa and West Africa, the United Nations, the diamond industry and diamond-trading nations introduced the Kimberley Process in 2002, which is aimed at ensuring that conflict diamonds do not become intermixed with the diamonds not controlled by such rebel groups, by providing documentation and certification of diamond exports from producing countries to ensure that the proceeds of sale are not being used to fund criminal or revolutionary activities. Although the Kimberley Process has been moderately successful in limiting the number of conflict diamonds entering the market, conflict diamonds smuggled to market continue to persist to some degree (approx. 2–3% of diamonds traded today are possible conflict diamonds). According to the 2006 book The Heartless Stone , two major flaws still hinder the effectiveness of the Kimberley Process: the relative ease of smuggling diamonds across African borders and giving phony histories, and the violent nature of diamond mining in nations which are not in a technical state of war and whose diamonds are therefore considered "clean."

The Canadian Government has setup a body known as Canadian Diamond Code of Conduct to help authenticate Canadian diamonds. This is a very stringent tracking system of diamonds and helps protect the 'conflict free' label of Canadian diamonds.

Currently, gem production totals nearly 30 million carats (6,000 kg) of cut and polished stones annually, and over 100 million carats (20,000 kg) of mined diamonds are sold for industrial use each year, as are about 100,000 kg of synthesized diamond.

Distribution

The Diamond Trading Company , or DTC, is a subsidiary of De Beers and markets rough diamonds produced both by De Beers mines and other mines from which it purchases rough diamond production. Once purchased by sightholders, diamonds are cut and polished in preparation for sale as gemstones. The cutting and polishing of rough diamonds is a specialized skill that is concentrated in a limited number of locations worldwide. Traditional diamond cutting centers are Antwerp , Amsterdam, Johannesburg, New York, and Tel Aviv. Recently, diamond cutting centers have been established in China, India, and Thailand. Cutting centers with lower cost of labor, notably Surat in Gujarat, India, handle a larger number of smaller carat diamonds, while smaller quantities of larger or more valuable diamonds are more likely to be handled in Europe or North America. The recent expansion of this industry in India, employing low cost labor, has allowed smaller diamonds to be prepared as gems in greater quantities than was previously economically feasible.

Diamonds which have been prepared as gemstones are sold on diamond exchanges called bourses . There are 26 registered diamond bourses. This is the final tightly controlled step in the diamond supply chain; wholesalers and even retailers are able to buy relatively small lots of diamonds at the bourses, after which they are prepared for final sale to the consumer. Diamonds can be sold already set in jewelry, or as is increasingly popular, sold unset ("loose"). According to the Rio Tinto Group , in 2002 the diamonds produced and released to the market were valued at US$9 billion as rough diamonds, US$14 billion after being cut and polished, US$28 billion in wholesale diamond jewelry , and retail sales of US$57 billion.

5.United States

The Crater of Diamonds State Park is an Arkansas State Park located near Murfreesboro in Pike County, Arkansas, USA containing the only diamond bearing site in the world that is open to the public.

Synthetics, simulants, and enhancements

Natural diamonds have formed naturally within the earth. Synthetic diamonds are created by a man-made process. A diamond simulant is defined as a non-diamond material that is used to simulate the appearance of a diamond. Diamond-simulant gems are often referred to as diamante.

The gemological and industrial uses of diamond have created a large demand for rough stones. The demand for industrial diamonds has long been satisfied in large part by synthetic diamonds , which have been manufactured by various processes for more than half a century. However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size.

The majority of commercially available synthetic diamonds are yellow in color and produced by so called High Pressure High Temperature (HPHT) processes. The yellow color is caused by nitrogen impurities. Other colors may also be reproduced such as blue, green or pink which are a result of the addition of boron or from irradiation after synthesis.

At present the annual production of gem quality synthetic diamonds is only a few thousand carats, whereas the total production of natural diamonds is around 120 million carats. Although the production of colorless synthetic diamonds is dwarfed by that of natural diamonds, one can only find one fancy colored diamond for every 10.000 colorless ones. Since almost the complete production of synthetic diamonds consists of fancy diamonds, there is a high probability that the larger fancy colored diamonds (over 1.5 carats) will be synthetic.

Today, trained gemologists can generally also distinguish between natural diamonds and synthetic diamonds. Although synthetic and natural diamonds are theoretically identical and indistinguishable from each other, diamonds from each of the two categories usually incorporate their own characteristic imperfections, arising from the circumstances of their creation, that allow them to be distinguished from each other. In the case of synthetic diamonds, for example, depending on the method of production (either HPHT produced or CVD produced) and the color of the diamond (colored, D-Z color range or D-J color range), several methods of identification can be attempted by a gemologist or gemlab: CVD diamonds can usually be identified by an orange fluorescence, D-J colored diamonds can be screened through the Swiss Gemological Organization's (SSEF) Diamond Spotter, and stones in the D-Z color range can be examined through the DiamondSure UV/visible spectrometer which is a tool developed by De Beers. Similarly, natural diamonds usually have minor imperfections and flaws, such as inclusions of foreign material, that are not seen in synthetic diamonds. The origin of a truly perfect diamond (natural or synthetic) cannot be determined and is largely moot, but perfect diamonds are currently rare from both sources.

A diamond's gem quality, which is not as dependent on material properties as industrial applications, has invited both imitation and the invention of procedures to enhance the gemological properties of natural diamonds. Materials which have similar gemological characteristics to diamond but are not mined or synthetic diamond are known as diamond simulants . The most familiar diamond simulant to most consumers is cubic zirconia (commonly abbreviated as CZ); recently moissanite has also gained popularity and has often been mischaracterized as a diamond simulant, although it is sold and retailed as a replacement for diamond. Both CZ and moissanite are synthetically produced. However, CZ is a diamond simulant. Diamond enhancements are specific treatments, performed on natural diamonds (usually those already cut and polished into a gem), which are designed to better the gemological characteristics of the stone in one or more ways.

These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond.

Currently, trained gemologists with appropriate equipment are able to distinguish natural diamonds from simulant diamonds, and they can identify all enhanced natural diamonds. Coatings are more and more used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance, which is heavily advertised, is what scientists refer to as "diamond-like carbon". This is an amorphous carbonaceous material that has some physical properties which are similar to that of the diamond. Advertising suggests (righfully so or not) that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant. However, modern techniques such as Raman Spectroscopy should easily identify such as treatment.

Producing large synthetic diamonds threatens the business model of the diamond industry, and the ultimate effect of the ready availability of gem-quality diamonds at low cost in the future is hard to predict at this time. The screening machine use for referring treated or enhanced diamonds as well as synthetics is the DiamondSure , and the definitive analytical machine is the DiamondView produce by the DTC and supplied marketed by the GIA. All of the major diamond testing laboratories world wide are required to have these machines.

Emerald Author Ganesh

Emerald

Emerald with host rock General Category Beryl variety Beryllium aluminium sil icate with chromium, Chemical formula Be 3Al 2(SiO 3)6::Cr Identification Color Green Crystal habit Hexagonal Crystals Crystal system Hexagonal Cleavage Poor Basal Cleavage (Seldom Visible) Fracture Conchoidal Mohs Scale hardness 7.5 - 8.0 Luster Vitreous Refractive index 1.576 - 1.582 Pleochroism Distinct, Blue-Green/Yellow-Green Streak White Specific gravity 2.70 - 2.78

Emeralds are a variety of the mineral beryl (Be 3Al 2(SiO 3)6,) colored green by trace amounts of chromium and sometimes vanadium. Beryl has a hardness of 7.5 - 8 on the 10 point Mohs scale of mineral hardness. Most emeralds are highly included, so their brittleness (resistance to breakage) is classified as generally poor. The origin of the word "emerald" is said to be a Sanskrit word meaning "green".

Contents

• 1 Properties determining value • 2 Treatments • 3 Emerald localities • 4 Synthetic emerald • 5 Emerald in different cultures, and Emerald lore o 5.1 High Priest Breastplate • 6 Famous emeralds

1.Properties determining value

Emeralds come in many shades of green and bluish green. There is a wide spectrum of clarity, dependent on the inclusions and fractures in the crystal. Clear stones with dark yet vibrant color command the highest prices. Almost all emeralds contain numerous flaws, cracks, and inclusions, which can negatively affect the clarity. These are given the name "jardin", from the French word for garden. The value of an emerald depends on cut, color, clarity, and carat . Currently the best emeralds come from the Muzo mine in Colombia .

2.Treatments

Most emeralds are oiled as part of the post lapidary process, in order to improve their clarity. Cedar oil, having a similar refractive index , is often used in this generally accepted practice. The U.S. Federal Trade Commission requires the disclosure of this treatment when a treated emerald is sold. The amount of oil entering an emerald microfissure is roughly equivalent to the size of a period (full stop) in print. The use of green-tinted oil is generally not considered acceptable by the gem trade.

3.Emerald localities

Emeralds in antiquity were mined by the Egyptians and in Austria , as well as Swat in northern Pakistan.

A rare type of emerald known as a trapiche emerald is occasionally found in the mines of Colombia . A trapiche emerald exhibits a "star" pattern; it has raylike spokes of dark carbon impurities that give the emerald a six-pointed radial pattern . It is named for the trapiche , a grinding wheel used to process sugarcane in the region. Colombian emeralds are generally the most prized due to their transparency and fire. Some of the most rare emeralds come from three main emerald mining areas in Colombia: Muzo, Coscuez, and Chivor. Fine emeralds are also found in other countries, such as Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Afghanistan and Russia. In the US, emeralds can be found in North Carolina. In 1998, emeralds were discovered in the Yukon, Canada .

4.Synthetic emerald

Emerald showing its hexagonal structure

Emerald is a rare and valuable gemstone and, as such, it has provided the incentive for developing synthetic emeralds. Both hydrothermal and flux-growth synthetics have been produced, and a method has been developed for producing an emerald overgrowth on colorless beryl. The first commercially successful emerald synthesis process was that of Carroll Chatham. Because Chatham's emeralds do not have any water and contain traces of vanadate, molybdenum and vanadium, a lithium vanadate flux process is probably involved. The other large producer of flux emeralds is Pierre Gilson Sr., which has been on the market since 1964. Gilson's emeralds are usually grown on natural colorless beryl seeds which become coated on both sides. Growth occurs at the rate of 1 mm per month and a typical seven-month growth run produces emerald crystals of 7 mm of thickness (Nassau, K. Gems Made By Man, 1980).

Hydrothermal synthetic emeralds have been attributed to IG Farben , Nacken, Tairus and others, but the first satisfactory commercial product was that of Johann Lechleitner of Innsbruck, Austria, which appeared on the market in the 1960s. These stones were initially sold under the names "Emerita" and "Symeralds", and they were grown as a thin layer of emerald on top of natural colorless beryl stones. Although not much is known about the original process, it is assumed that Leichleitner emeralds were grown in acid conditions.

Later, from 1965 to 1970, the Linde Division of Union Carbide produced completely synthetic emeralds by hydrothermal synthesis. According to their patents (US3,567,642 and US3,567,643), acidic conditions are essential to prevent the chromium (which is used as the colorant) from precipitating. Also, it is important that the silicon containing nutrient be kept away from the other ingredients in order to prevent nucleation and confine growth to the seed crystals. Growth occurs by a diffusion-reaction process, assisted by convection. Typical growth conditions include pressures of 700-1400 bars at temperatures of 500 to 600 °C with a temperature gradient of 10 to 25 °C. Growth rates as fast as 1/3 mm per day can be attained.

Luminescence in ultraviolet light is considered a supplementary test when making a natural vs. synthetic determination, as many, but not all, natural emeralds are inert to ultraviolet light . Many synthetics are also UV inert.

Synthetic emeralds are often referred to as "created", as their chemical and gemological composition is the same as their natural counterparts. The U.S. Federal Trade Commission (FTC) has very strict regulations as to what can and what cannot be called "synthetic" stone. The FTC says: "§ 23.23(c) It is unfair or deceptive to use the word "laboratory-grown," "laboratory-created," "[manufacturer name]-created," or "synthetic" with the name of any natural stone to describe any industry product unless such industry product has essentially the same optical, physical, and chemical properties as the stone named."

Wispy veil-like inclusions are common in flux-grown synthetic emeralds.

5.Emerald in different cultures, and Emerald lore

The Gachala Emerald is one of the largest gem emeralds in the world at 858 carats (172 g). This stone was found in 1967 at La Vega de San Juan mine in Gachalá, Colombia. It is housed at the National Museum of Natural History of the Smithsonian Institution in Washington DC.

Emerald is regarded as the traditional birthstone for May, as well as the traditional gemstone for the astrological signs of Taurus , Cancer and sometimes Gemini. One of the more quaint anecdotes on emeralds was by the 16th century historian Brantome, who referred to the many impressive emeralds the Spanish under Cortez had brought back to Europe from Latin America. On one of Cortez most famous emeralds he had the text engraved Inter Natos Mulierum non sur-rexit mayor (Among them borne of woman there hath not arisen a greater Man. XI, 11) which referred to John the Baptist.

Brantome considered engraving such a beautiful and simple product of nature sacrilegious and considered this act the cause for Cortez loss of an extremely precious pearl (to which he dedicated a work A beautiful and incomparable pearl ) and even for the death of King Charles IX who died soon after.

High Priest Breastplate

In Exodus chapters 28 and 39, a number of precious stones are mentioned to be placed in the High Priest's Breastplate, representing the different tribes of Israel. This is generally considered to be (one of) the origin(s) of our present day tradition of birthstones .

According to Rebbenu Bachya , and the King James Version , the Hebrew word Nofech in Exodus 28:18 means Emerald , and was the stone on the Hoshen representing the tribe of Judah. However, the Septuagint translates the word as Anthrax , meaning coal , probably in reference to the colour of burning coal, and therefore many rabbinical sources, and most scholars, consider Nofech to mean a red garnet – traditionally called a carbuncle , which happens to be the Vulgate's translation of the word. There is a wide range of views among traditional sources about which tribe the stone refers to.

There are many complexities to identifying the Emerald as being the third stone or perhaps another stone on the breast plate. Multiple translations of the bible have created confusion about the nomenclature of the different stones. Another important fact is that in actuality there are 2 different breastplates made within a period of 800 years, and where it is assumed the first breastplate did not carry an Emerald but a green Felspar , and a real Emerald in the second breastplate. Finally the 12th stone in the Breastplate (which in the original text was actually listed as the 6th stone) has more generally been identified as Beryl which was already included in the group of stones generally referred to as Smaragdus by Theophrastus in the Greek era. Further unreferenced claims regarding the possibility of what gemstone the Emerald could really have been include Jasper, and even Rubies.

In some cultures, the emerald is the traditional gift for the 55th wedding anniversary . It is also used as a 20th and 35th wedding anniversary stone.

6.Famous emeralds

• Gachala Emerald (origin: Colombia) • Chalk Emerald (origin: Colombia) • Nidvin Emerald (origin: Colombia) • Duke of Devonshire Emerald (origin: Colombia) • Mackay Emerald • Greenshorkire Emerald • Edward the Confessor Emerald in the Imperial State Crown of Great Britain

Opal Author Ganesh

Opal

An opal bracelet. The stone size is 18 by 15 mm (0.7 by 0.6 inch).

General

Category Mineraloid

Chemical formula Hydrated silica . SiO 2·nH2O

Identification

White, black, red, orange, most of the full spectrum, Color colorless, iridescent . Very infrequently of a singular color

Crystal habit Irregular veins, in masses, in nodules

Crystal system Amorphous

Cleavage None

Fracture Conchoidal to uneven

Mohs Scale hardness 5.5–6.5

Luster Subvitreous to waxy

Polish luster Vitreous to resinous

1.450 (+.020, -.080) Mexican Opal may read as low as 1.37, Refractive index but typically reads 1.42–1.43

Single refractive, often an omalous double refractive due to Optical Properties strain

Birefringence None

Pleochroism None

black or white body color: inert to white to moderate light blue, green, or yellow in long and short wave. May also phosphoresce; common opal : ine rt to strong green or Ultraviolet fluorescence yellowish green in long and short wave, may phosphoresce; fire opal : inert to moderate greenish brown in long and short wave, may phosphoresce.

Absorption spectra green stones: 660nm, 470nm cutoff

Streak White

Specific gravity 2.15 (+.08, -.90)

Diagnostic Features darkening upon heating

Solubility hot saltwater , bases , methanol, humic acid, hydrofluoric acid

Diaphaneity opaque, translucent, transparent

The mineraloid opal is amorphous SiO 2·nH2O, hydrated silicon dioxide. The water content is usually between three and ten percent, but can be as high as 20%. Opal ranges from clear through white, gray, red, yellow, green, shore, blue, magenta, brown, and black. Of these hues, red and black are the most rare and dear, whereas white and green are the most common; these are a function of growth size into the red and infrared wavelengths—see precious opal. Common opal is truly amorphous, but precious opal does have a structural element. The word opal comes from the Latin opalus , by Greek òpalliòs , and is from the same root as Sanskrit upálá for "stone", originally a millstone with upárá for slab. (see Upal). Opals are also Australia's national gemstone.

Opal is a mineraloid gel which is deposited at relatively low temperature and may occur in the fissures of almost any kind of rock , being most commonly found with limonite, sandstone, rhyolite, and basalt.

Opal is one of the mineraloids that can form or replace fossils . The resulting fossils, though not of any extra scientific interest, appeal to collectors.

Contents

• 1 Precious opal • 2 Common opal • 3 Other varieties of opal • 4 Sources of opal • 5 Synthetic opal • 6 Local atomic structure of opals o 6.1 Microcrystalline opal o 6.2 Non-crystalline opal • 7 Historical superstitions • 8 Opals in popular culture • 9 Famous opals

1. Precious opal

Precious opal shows a variable interplay of internal colors and does have an internal structure. At the micro scale precious opal is composed of silica spheres some 150 to 300 nm in diameter in a hexagonal or cubic closed-packed lattice. These ordered silica spheres produce the internal colors by causing the interference and diffraction of light passing through the microstructure of opal (Klein and Hurlbut, 1985, p. 444). It is the regularity of the sizes of the spheres, and of the packing of these spheres that determines the quality of precious opal. Where the distance between the regularly packed planes of spheres is approximately half the wavelength of a component of visible light, the light of that wavelength may be subject to diffraction from the grating created by the stacked planes. The spacing between the planes and the orientation of planes with respect to the incident light determines the colors observed. The process can be described by Bragg's Law of diffraction. Visible light of diffracted wavelengths cannot pass through large thicknesses of the opal. This is the basis of the optical band gap in a photonic crystal, of which opal is the best known natural example.

Precious opal consists of spheres of silica of fairly regular size, packed into close- packed planes which are stacked together with characteristic dimensions of several hundred nm.

In addition, microfractures may be filled with secondary silica and form thin lamellae inside the opal during solidification. The term opalescence is commonly and erroneously used to describe this unique and beautiful phenomenon, which is correctly termed play of color . Contrarily, opalescence is correctly applied to the milky, turbid appearance of common or potch opal. Potch does not show a play of color.

The veins of opal displaying the play of color are often quite thin, and this has given rise to unusual methods of preparing the stone as a gem. An opal doublet is a thin layer of colorful material, backed by a black mineral, such as ironstone, basalt or obsidian. The darker backing emphasizes the play of color, and results in a more attractive display than a lighter potch. Given the texture of opals, they can be quite difficult to polish to a reasonable lustre. The triplet cut backs the colored material with a dark backing, and then has a domed cap of clear quartz (rock crystal) or plastic on top, which takes a high polish, and acts as a protective layer for the relatively fragile opal. Opal doublets and triplets are not classed as precious opal.

2.Common opal

Besides the gemstone varieties that show a play of color, there are other kinds of common opal such as the milk opal, milky bluish to greenish (which can sometimes be of gemstone quality); resin opal, honey-yellow with a resinous luster; wood opal, caused by the replacement of the organic material in wood with opal; menilite brown or grey; hyalite, a colorless glass-clear opal sometimes called Muller's Glass; geyserite, (siliceous sinter) deposited around hot springs or geysers; and diatomite or diatomaceous earth, the accumulations of diatom shells or tests.

3.Other varieties of opal

Fire opal , or Girasol, is a translucent to semi-opaque stone that is generally yellow to bright orange and sometimes nearly red and displays pleochroism at certain angles.

Peruvian opal (also called blue opal) is a semi-opaque to opaque blue-green stone found in Peru which is often cut to include the matrix in the more opaque stones. It does not display pleochroism.

Boulder opal carving of a walrus, showing flashes of color from the exposed opal. The carving is 9 cm (3.5 inches) long.

4.Sources of opal

Until the nineteenth century the only source of precious opal known to Europeans was the mining district of Červenica in Slovakia .

Opal without play of color is very common and can be found all over the world, unlike precious opal deposits that are in greater scope found today only in Australia, U.S., Mexico and Ethiopia.

Australia produces around 97% of the world’s opal. 90% is called ‘light opal’ or white and crystal opal. White makes up 60% but not all the opal fields produce white opal; Crystal opal or pure hydrated silica makes up 30%; 8% is black and only 2% is boulder opal.

The town of Coober Pedy in South Australia is a major source of opal. Another Australian town, Lightning Ridge in New South Wales, is the main source of black opal, opal containing a predominantly dark background (dark-gray to blue-black displaying the play of color ). Boulder opal consists of concretions and fracture fillings in a dark siliceous ironstone matrix. It is found sporadically in western Queensland, from Kynuna in the north, to Yowah and Koroit in the south.

Multi-color rough opal specimen from Virgin Valley, Nevada, USA

Fire opal is found mostly in Mexico and Mesoamerica . In South America opal discovered in 1930 in a city called Pedro II in Brazil is still produced. In Honduras there was also some fine black opal mined from volcanic ash deposits. This opal is known for its stability.

The Virgin Valley Opal Fields Of Humboldt County in Northern Nevada produce a wide variety black, crystal, white, and fire opal.The Fire Opal mined from this locality is designated as the official gemstone of the State of Nevada. Most precious opals are wood replacements. Many specimens have a high water content, and as a result, have a greater tendency to desiccate and crack than most precious opal. Discovered in 1904 the mines are still producing gem materials in large amounts to hundreds of seasonal visitors. Three Fee Dig Mines provide the general public an opportunity to dig the gems themselves. The largest black opal in the Smithsonian Museum, possibly worth in excess of $1 million, comes from the Royal Peacock Opal Mine in the Virgin Valley.

Another source of white base opal in the United States is Spencer, Idaho. A high percentage of the opal found there occurs in thin layers. As a result, most of the production goes into the making of doublets and triplets.

Other significant deposits of precious opal around the world can be found in the Czech Republic, Slovakia, Hungary, Turkey, Indonesia, Brazil, Honduras, Guatemala, Nicaragua and Ethiopia.

5.Synthetic opal

As well as occurring naturally, opals of all varieties have been synthesized experimentally and commercially. The discovery of the ordered sphere structure of precious opal led to its synthesis by Pierre Gilson in 1974 (Klein and Hurlbut, 1985, p.528). The resulting material is distinguishable from natural opal by its regularity; under magnification, the patches of color are seen to be arranged in a "lizard skin" or "chicken wire" pattern. Synthetics are further distinguished from naturals by the former's lack of fluorescence under UV light. Synthetics are also generally lower in density and are often highly porous; some may even stick to the tongue.

Two notable producers of synthetic opal are the companies Kyocera and Inamori of Japan. Most so-called synthetics, however, are more correctly termed imitations , as they contain substances not found in natural opal (e.g., plastic stabilizers). The imitation opals seen in vintage jewellery are often "Slocum Stone" consisting of laminated glass with bits of foil interspersed.

The Hamamatsu Photonics Group will utilise the International Space Station's Japanese Experiment Module in 2006 to grow perfect crystalline opals in microgravity over four months, as compared with five million years for naturals. Such opals will be the object of study and elements for optical filters, displays, and data storage.

6.Local atomic structure of opals

The lattice of spheres of opal that cause the interference with light are several hundred times larger than the fundamental structure of crystalline silica. As a mineraloid, there is no unit cell that describes the structure of opal.

Nevertheless, opals can be roughly divided into those that show no signs of crystalline order, i.e., amorphous opal, and those that show signs of the beginning of crystalline order, commonly termed cryptocrystalline or microcrystalline opal (Graetsch, 1994). Dehydration experiments and infrared spectroscopy have shown that most of the H 2O in the formula of

SiO 2.nH 2O of opals is present in the familiar form of clusters of molecular water. Isolated water molecules, and silanols, structures such as Si-O-H, generally form a lesser proportion of the total and can reside near the surface or in defects inside the opal.

The structure of low-pressure polymorphs of anhydrous silica consist of frameworks of fully-corner bonded tetrahedra of SiO 4. The higher temperature polymorphs of silica cristobalite and tridymite are frequently the first to crystallize from amorphous anhydrous silica, and the local structures of microcrystalline opals also appear to be closer to that of cristobalite and tridymite than to quartz. The structures of tridymite and cristobalite are closely related and can be described as hexagonal and cubic close-packed layers. It is therefore possible to have intermediate structures in which the layers are not regularly stacked.

The crystal structure of crystalline α-cristobalite. Locally, the structures of some opals, opal-C, are similar to this.

Microcrystalline opal

Opal-CT has been interpreted as consisting of clusters of stacking of cristobalite and tridymite over very short length scales. The spheres of opal in opal-CT are themselves made up of tiny microcrystalline blades of cristobalite and tridymite. Opal-CT has occasionally been further subdivided in the literature. Water content may be as high as 10 wt%. Lussatite is a synonym.

Opal-C is interpreted as consisting of localized order of α-cristobalite with a lot of stacking disorder. Typical water content is about 1.5wt%. Lussatine is a synonym.

Non-crystalline opal

Two broad categories of non-crystalline opals, sometimes just referred to as opal-A, have been proposed

Opal-AG : Aggregated spheres of silica, with water filling the space in between. Precious opal and potch opal are generally varieties of this, the difference being in the regularity of the sizes of the spheres and their packing.

Opal-AN : Water-containing amorphous silica-glass. Hyalite is a synonym.

Non-crystalline silica in siliceous sediments is reported to gradually transform to opal-CT and then opal-C as a result of diagenesis, due to the increasing overburden pressure in sedimentary rocks, as some of the stacking disorder is removed (Cady et al. , 1996)PDF (2.03 MiB).

7.Historical superstitions

In the Middle Ages, opal was considered a stone that could provide great luck because it was believed to possess all the virtues of each gemstone whose color was represented in the color spectrum of the opal. However, modern superstition attributes bad luck to the stone, though some believe this is avoided if opal is the owner's birthstone (that is, the owner was born in October) or if the stone is a gift. Even under the last czar at the beginning of the 20th century, it was believed that when a Russian of any sex, of any rank, saw an opal, amongst other goods offered for sale, he or she would not buy anything more, since, in the judgement of subjects of the czar, the opal embodied the evil eye. It's possible that the stone's extreme fragility (when compared to other gemstones) has contributed to this bad reputation.

8.Opals in popular culture

The opal is the official gemstone of South Australia and the Commonwealth of Australia, and the country's women's national team in basketball is nicknamed The Opals .

The official state gem stone for Nevada is precious black Fire Opal, in recognition of the black opal found in Virgin Valley, Humboldt County, Nevada.

Opal is the traditional birthstone of the month of October.

9.Famous opals

• The Andamooka Opal, presented to Queen Elizabeth II, also known as the Queen's Opal • The Aurora Australis Opal, considered to be the most valuable black opal • The Black Prince Opal, originally known as Harlequin Prince • The Empress of Australia Opal • The Fire Queen Opal • The Flame Queen Opal • The Flamingo Opal • The Halley's Comet Opal, the world's largest uncut black opal • The Jupiter Five Opal • The Olympic Australis Opal, reported to be the largest and most valuable gem opal ever found • The Pride of Australia Opal, also known as the Red Emperor Opal • The Red Admiral Opal, also known as the Butterfly Stone

Pearl Author Ganesh

A black pearl and a shell of the black-lipped pearl oyster

Saltwater pearl oyster farm, Seram, Indonesia

A pearl is a hard, rounded object produced within the soft tissue (specifically the mantle ) of a living shelled mollusk. Just like the shell of mollusks, a pearl is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes of pearls occur, see baroque pearl.

The finest quality pearls have been highly valued as gemstones and objects of beauty for many centuries, and the word pearl has become a metaphor for something rare, fine, and admirable.

Biologically speaking, under the right set of circumstances, almost any shelled mollusk can produce some kind of "pearl", however, most of these molluscan "pearls" have no luster or iridescence . In fact the great majority of mollusk species produce pearls which are not attractive to look at, and are sometimes not even very durable, such that they usually have no value at all, except perhaps to a scientist, or as a curiosity. These objects would be referred to as "calcareous concretions" by a gemologist, even though a malacologist would still consider them to be pearls. One unusual example of "calcareous concretions" which nonetheless can sometimes have value, are the "pearls" which very rarely are found growing between the mantle and the shell of the queen conch or pink conch, Strombus gigas , a large sea snail or marine gastropod from the Caribbean Sea. These "pearls" are a by-product of the conch fishing industry, and the best of them show some chatoyance. However, true iridescent pearls, the most desirable pearls, are all produced by two very different groups of molluscan bivalves or clams . One group lives in the sea: the pearl oysters. The other, very different group of bivalves live in freshwater; these are the freshwater or river mussels.

Saltwater pearls can grow in several species of marine pearl oysters in the family Pteriidae. Freshwater pearls grow within certain (but by no means all) species of freshwater mussels in the order Unionida, the families Unionidae and Margaritiferidae. All of these bivalves are able to make true pearls because they have a thick inner shell layer composed of "mother of pearl" or nacre. The mantle of the living bivalve can create a pearl in the same way that it creates the pearly inner layer of the shell.

Fine gem quality saltwater and freshwater pearls can and do sometimes occur completely naturally, but this is a rare occurrence. Many hundreds of pearl oysters or pearl mussels have to be gathered and opened (killed) in order to find even one pearl, and for many centuries that was the only way pearls were obtained. This was the main reason why pearls fetched such extraordinary prices in the past. In modern times however, almost all the pearls for sale were formed with a good deal of expert intervention from human pearl farmers.

A true pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell. A "natural pearl" is one that formed without any human intervention at all, in the wild, and these are very rare. A "cultured pearl" on the other hand, is one that has been formed on a pearl farm. The great majority of pearls on the market are cultured pearls. Imitation or fake pearls are also widely sold in inexpensive jewelry, but the quality of the iridescence is usually very poor, and generally speaking, fake pearls are usually quite easy to distinguish from the real thing. True pearls have long been greatly valued as gemstones . They have been harvested, or more recently cultivated, primarily for use in jewelry but were also historically worn stitched onto lavish clothing as worn, for example, by royalty. Pearls have also been crushed and used in cosmetics, medicines, or in paint formulations. Pearl is considered to be the birthstone for June .

Contents

• 1 Physical properties • 2 Freshwater and saltwater pearls o 2.1 Creation of a pearl o 2.2 Natural pearls o 2.3 Cultured pearls o 2.4 Gemological identification o 2.5 Value of a natural pearl o 2.6 Origin of a natural pearl o 2.7 Different types of cultured pearls • 3 Largest pearl • 4 History • 5 Jewelry • 6 Religious references o 6.1 Islamic references o 6.2 Hindu astrological belief in natural pearls

1. Physical properties

Akoya pearl grafting shed in Xuwen, China.

The unique luster of pearls depends upon the reflection and refraction of light from the translucent layers. The thinner and more numerous the layers in the pearl, the finer the luster. The iridescence that pearls display is caused by the overlapping of successive layers, which breaks up light falling on the surface.

Pearls are often white or cream, but the color can vary quite a lot according to the natural color of the nacre in the various species of mollusk used. Thus pearls can also be black, or various pastel shades. In addition, pearls (especially freshwater pearls) can be dyed yellow, green, blue, brown, pink, purple, or black.

2.Freshwater and saltwater pearls

Freshwater and saltwater pearls may sometimes look quite similar but they come from very different sources.

Freshwater pearls are formed in various species of freshwater mussels ( Unionidae ), which live in lakes, rivers, ponds and other bodies of fresh water. These freshwater pearl mussels occur not only in hotter climates but also in colder more temperate areas such as Scotland, see freshwater pearl mussel. However, most freshwater cultured pearls sold today come from China.

Saltwater pearls grow within pearl oysters ( Pteriidae ) which live in tropical oceans. Saltwater pearl oysters are usually cultivated in protected lagoons . The three main types of saltwater pearls are Akoya, South Sea and Tahitian.

Creation of a pearl

The difference between natural and cultured pearls focuses on whether the pearl was created spontaneously by nature—without human intervention—or with human aid. Pearls are formed inside the shell of certain bivalve mollusks. As a response to an irritant inside its shell, the mollusk creates a pearl to seal off the irritation.

The mantle of the mollusk deposits layers of calcium carbonate (CaCO 3) in the form of the minerals aragonite or calcite (both crystalline forms of calcium carbonate) held together by an organic horn-like compound called conchiolin. This combination of calcium carbonate and conchiolin is called nacre, or as most know it, mother-of-pearl. The commonly held belief that a grain of sand acts as the irritant is in fact rarely the case. Typical stimuli include organic material, parasites, or even damage that displaces mantle tissue to another part of the animal's body.

These small particles or organisms enter the animal when the shell valves are open for feeding or respiration. In cultured pearls, the irritant is typically a cut piece of the mantle epithelium, together with processed shell beads, the combination of which the animal accepts into its body.

Natural pearls

Cross section illustration showing natural and cultured pearls.

Natural pearls are nearly 100% nacre . It is thought that natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters a bivalve mollusk, and settles inside the shell. The mollusk, being irritated by the intruder, secretes the calcium carbonate substance called nacre to cover the irritant. This secretion process is repeated many times, thus producing a pearl. Natural pearls come in many shapes, with round ones being comparatively rare.

Cultured pearls

Cultured pearls (nucleated and non-nucleated or tissue nucleated cultured pearls) and imitation pearls can be distinguished from natural pearls by X-ray examination. Nucleated cultured pearls are often 'pre-formed' as they tend to follow the shape of the implanted shell bead nucleus. Once the pre-formed beads are inserted into the oyster, it secretes a few layers of nacre around the outside surface of the implant before it is removed after six months or more. When a nucleated cultured pearl is X-rayed it will reveal a different structure to that of a natural pearl. It exhibits a solid center with no concentric growth rings, compared to a solid center with growth rings.

Gemological identification

A well equipped gem testing laboratory is able to separate natural pearls from cultured pearls by examining the center of a pearl, and the growth rings separated by conchiolin layers. The differentiation of a natural pearl or tissue-nucleated cultured pearl can be difficult without a gemological X-ray .

All natural and cultured pearls can be distinguished from imitation pearls using a microscope . Another accurate method of testing for imitations is to rub the pearl against the surface of a front tooth. Imitation pearls are completely smooth, but natural and cultured pearls are composed of nacre platelets, which feel slightly gritty.

Value of a natural pearl

Quality natural pearls are very rare jewels. The actual value of a natural pearl is determined in the same way as it would be for other "precious" gems. The valuation factors include size, shape, quality of surface, orientation, and luster.

Single natural pearls are often sold as a collector's item, or set as centerpieces in unique jewelry. Very few matched strands of natural pearls exist, and those that do often sell for hundreds of thousands of dollars. Yachtsman and financier Cartier purchased the landmark Cartier store on Fifth Avenue in New York for $100 cash and a double strand of matched natural pearls valued at $1 million.

Keshi pearls, although they often occur by chance, are not considered natural pearls. They are a byproduct of the culturing process, and hence do not happen without human intervention. These pearls are quite small: typically a few millimeters in size. Keshi pearls are produced by many different types of marine mollusks and freshwater mussels in China.Today many "keshi" pearls are actually intentional, with post-harvest shells returned to the water to regenerate a pearl in the existing pearl sac.

Origin of a natural pearl

Previously natural pearls were found in many parts of the world. Present day natural pearling is confined mostly to seas off Bahrain . Australia also has one of the world's last remaining fleets of pearl diving ships. Australian pearl divers dive for south sea pearl oysters to be used in the cultured south sea pearl industry. The catch of pearl oysters is similar to the numbers of oysters taken during the natural pearl days. Hence significant numbers of natural pearls are still found in the Australian Indian Ocean waters from wild oysters. X- Ray examination is required to positively verify natural pearls found today.

Different types of cultured pearls

Nuclei from Toba Pearl Island, Japan

Black pearls, frequently referred to as Black Tahitian Pearls, are highly valued because of their rarity; the culturing process for them dictates a smaller volume output and can never be mass produced. This is due to bad health and/or non-survival of the process, rejection of the nucleus (the small object such as a tiny fish, grain of sand or crab that slips naturally inside an oyster's shell or inserted by a human), and their sensitivity to changing climatic and ocean conditions. Before the days of cultured pearls, black pearls were rare and highly valued for the simple reason that white pearl oysters rarely produced natural black pearls, and black pearl oysters rarely produced any natural pearls at all. Since pearl culture technology, the black pearl oyster found in Tahiti and many other Pacific Island area has been extensively used for producing cultured pearls. The rarity of the black cultured pearl is now a "comparative" issue. The black cultured pearl is rare when compared to Chinese freshwater cultured pearls, and Japanese and Chinese Akoya cultured pearls, and is more valuable than these pearls. However, it is more abundant than the south sea pearl, which is more valuable than the black cultured pearl. This is simply due to the fact that the black pearl oyster Pinctada margaritifera is far more abundant than the elusive, rare, and larger south sea pearl oyster - Pinctada maxima , which cannot be found in lagoons, but which must be dived for in a rare number of deep ocean habitats. Black cultured pearls from the black pearl oyster — Pinctada margaritifera — are NOT south sea pearls, although they are often mistakenly described as black south sea pearls. In the absence of an official definition for the pearl from the black oyster, these pearls are usually referred to as "black Tahitian pearls". The correct definition of a south sea pearl — as described by CIBJO and the GIA — is a pearl produced by the Pinctada maxima pearl oyster. South sea pearls are the color of their host Pinctada maxima oyster — and can be white, silver, pink, gold, cream, and any combination of these basic colors, including overtones of the various colors of the rainbow displayed in the pearl nacre of the oyster shell itself.

3.Largest pearl

The largest "pearl" ever found came from the Philippines in 1934. Although referred to as a pearl, and formed naturally, this is not pearly; it is a non-nacreous calcareous concretion from a clam, not a pearl oyster. In other words, gemologically speaking, it is not considered to be a pearl, although biologically speaking it is one.

It weighs 14 lb (6.4 kg) and was discovered by an anonymous Filipino Muslim diver off the island of Palawan in 1934. Later, a Palawan chieftain gave the pearl to Wilbur Dowell Cobb in 1936 as a gift for having saved the life of his son. The pearl had been named the "Pearl of Allah" by the Muslim tribal chief, because it resembled a turbaned head.

A legend claims that the pearl is actually the Pearl of Lao-Tzu, a cultured mabe pearl created with a carved amulet and progressively grafted into several giant clams, but then lost due to a shipwreck in 1745, only to be rediscovered in 1934.This legend has been discredited, however. The pearl is the product of a giant clam, Tridacna gigas, which cannot be grafted. The pearl is also a whole pearl, not a mabe, and whole pearl culturing technology is only 100 years old.

4.History

For thousands of years, most seawater pearls were retrieved by divers working in the Indian Ocean, in areas like the Persian Gulf, the Red Sea, and in the Gulf of Mannar (by the ancient Tamils).

Catching of pearls , Bern Physiologus (IX century)

When Spanish conquistadors arrived in the Western Hemisphere, they discovered that around the islands of Cubagua and Margarita, some 200 km north of the Venezuelan coast, was an extensive bed of pearls. One of them, the Peregrina, was offered to the Spanish queens. This pearl later became very famous when Richard Burton purchased it for his wife Elizabeth Taylor . Margarita pearls are extremely difficult to find today and are known for their unique yellowish color. The most famous Margarita necklace that any one can see today is the one that then Venezuelan President Romulo Betancourt gave to Jacqueline Kennedy when she and her husband, President John F. Kennedy paid an official visit to Venezuela.

Before the beginning of the 20th Century, pearl hunting was the most common way of harvesting pearls. Divers manually pulled oysters from ocean floors and river bottoms and checked them individually for pearls. Not all natural oysters produce pearls. In a haul of three tons, only three or four oysters will produce perfect pearls.

However, almost all pearls used for jewelry are cultured by planting a core or nucleus into pearl oysters . The pearls are usually harvested after one year for Akoya, and 2-4 years for Tahitian and South Sea, and 2-7 years for freshwater. This mariculture process was first developed by Tatsuhei Mise and Tokichi Nishikawa in Japan.

The nucleus is generally a polished bead made from freshwater mussel shell. Along with a small piece of mantle tissue from another mollusk to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of a saltwater mollusk. In freshwater perliculture, only the piece of tissue is used in most cases, and is inserted into the fleshy mantle of the host mussel. South Sea and Tahitian pearl oysters, also known as Pinctada maxima and Pinctada margaritifera , which survive the subsequent surgery to remove the finished pearl are often implanted with a new, larger nucleus as part of the same procedure and then returned to the water for another 2-3 years of growth. Despite the common misperception, Mikimoto did not patent the process of pearl culture. The accepted process of pearl culture was developed by a team of scientists at Tokyo University between 1907 and 1916. The team was headed by Tokichi Nishikawa and Tatsuhei Mise. Nishikawa was granted the patent in 1916, and married the daughter of Mikimoto. Mikimoto was able to use Nishikawa's technology. After the patent was granted in 1916, the technology was immediately commercially applied to akoya pearl oysters in Japan in 1916. Mise's brother was the first to produce a commercial crop of pearls in the akoya oyster. Mitsubishi's Baron Iwasaki immediately applied the technology to the south sea pearl oyster in 1917 in the Philippines, and later in Buton, and Palau. Mitsubishi was the first to produce a cultured south sea pearl - although it was not until 1928 that the first small commercial crop of pearls was successfully produced.

The original Japanese cultured pearls, known as akoya pearls, are produced by a species of small oysters, Pinctada fucata martensii , no bigger than 6 to 7 cm in size, hence akoya pearls larger than 10 mm in diameter are extremely rare and highly prized. Today a hybrid mollusk is used in both Japan and China in the production of akoya pearls. It is a cross between the original Japanese shell, and Pinctada chemnitzii of China.

China has recently overtaken Japan in akoya pearl production. Japan has all but ceased its production of akoya pearls smaller than 8mm. Japan maintains its status as a pearl processing center, however, and imports the majority of Chinese akoya pearl production. These pearls are then processed (often simply matched and sorted), relabeled as product of Japan, and exported.

In the past couple of decades, cultured pearls have been produced with larger oysters in the south Pacific and Indian Ocean . The largest pearl oyster is the Pinctada maxima , which is roughly the size of a dinner plate. South Sea pearls are characterized by their large size and silvery color. Sizes up to 14 mm in diameter are not uncommon. Australia is one of the most important sources of South Sea pearls. Mitsubishi commenced pearl culture with the south sea pearl oyster in 1916 as soon as the technology patent was commercialized. By 1931 this project was showing signs of success, but was upset by the death of Tatsuhei. Although the project was recommenced after Tatsuhei's death, the project was discontinued at the beginning of WWII before significant productions of pearls were achieved. After WWII, new south sea pearl projects were commenced in the early 1950s in Burma and Kuri Bay and Port Essington in Australia. Japanese companies were involved in all projects using technicians from the original Mitsubishi south sea pre-war projects. Despite often being described as black south sea pearls, Tahitian pearls are not south sea pearls. The correct definition of a south sea pearl is "the pearl produced by the Pinctada maxima pearl oyster."

In 1914, pearl farmers began culturing freshwater pearls using the pearl mussels native to Lake Biwa. This lake, the largest and most ancient in Japan, lies near the city of Kyoto. The extensive and successful use of the Biwa Pearl Mussel is reflected in the name Biwa pearls , a phrase which was at one time nearly synonymous with freshwater pearls in general.

Since the time of peak production in 1971, when Biwa pearl farmers produced six tons of cultured pearls, pollution and overharvesting have caused the virtual extinction of this animal. Japanese pearl farmers recently cultured a hybrid pearl mussel — a cross between the last remaining Biwa Pearl Mussels and a closely related species from China, the Cristaria plicata — in lake Kasumigaura. This industry closed in 2006 due to lake pollution.

Led by pearl pioneer John Latendresse and his wife Chessy, the United States began farming freshwater cultured pearls in the mid 1960's. National Geographic Magazine introduced the American cultured pearl as a commercial product in their August 1985 issue. The Tennessee pearl farm has emerged as a tourist destination in recent years.

In the 1990s, Japanese pearl producers also invested in producing cultured pearls with freshwater mussels in the region of Shanghai , China, and in Fiji. Freshwater pearls are characterized by the reflection of rainbow colors in the luster. Cultured pearls are also produced using abalone.

5.Jewelry

Girl with a Pearl Earring

The value of the pearls in jewelry is determined by a combination of the luster, color, size, lack of surface flaw and symmetry that are appropriate for the type of pearl under consideration. Among those attributes, luster is the most important differentiator of pearl quality according to jewelers. All factors being equal, however, the larger the pearl the more valuable it is. Large, perfectly round pearls are rare and highly valued. Teardrop- shaped pearls are often used in pendants.

Inexpensive, button-shape cultured freshwater pearls used in a necklace and bracelet.

Pearls come in eight basic shapes: round, semi-round, button, drop, pear, oval, baroque, and circled. Perfectly round pearls are the rarest and most valuable shape.

Semi-rounds are also used in necklaces or in pieces where the shape of the pearl can be disguised to look like it is a perfectly round pearl. Button pearls are like a slightly flattened round pearl and can also make a necklace, but are more often used in single pendants or earrings where the back half of the pearl is covered, making it look like a larger, round pearl.

Woman with a Pearl Necklace , by Jan Vermeer van Delft

Drop and pear shaped pearls are sometimes referred to as teardrop pearls and are most often seen in earrings, pendants, or as a center pearl in a necklace. Baroque pearls have a different appeal to them than more standard shapes because they are often highly irregular and make unique and interesting shapes. They are also commonly seen in necklaces. Circled pearls are characterized by concentric ridges, or rings, around the body of the pearl.

In general, cultured pearls are less valuable than natural pearls, and imitation pearls are less valuable than cultured pearls. One way that jewelers can determine whether a pearl is cultivated or natural is to have a gem lab perform an x-ray of the pearl. If the x-ray reveals a nucleus, the pearl is likely a bead-nucleated saltwater pearl. If no nucleus is present, but irregular and small dark inner spots indicating a cavity are visible, combined with concentric rings of organic substance, the pearl is likely a cultured freshwater. Cultured freshwater pearls can often be confused for natural pearls which present as homogeneous pictures which continuously darken toward the surface of the pearl. Natural pearls will often show larger cavities where organic matter has dried out and decomposed.

Some imitation pearls are simply made of mother-of-pearl , coral or conch, while others are made from glass and are coated with a solution containing fish scales called essence d'Orient. Although imitation pearls look the part, they do not have the same weight or smoothness as real pearls, and their luster will also dim greatly.

There is also a unique way of naming pearl necklaces. While most other necklaces are simply referred to by their physical measurement, strings of pearls have their own set of names that characterize the pearls based on where they hang when worn around the neck. A collar will sit directly against the throat and not hang down the neck at all; they are often made up of multiple strands of pearls. Pearl chokers nestle just at the base of the neck.

The size called a princess comes down to or just below the collarbone. A matinee of pearls falls just above the breasts. An opera will be long enough to reach the breastbone or sternum of the wearer, and longer still, a pearl rope is any length that falls down farther than an opera.

Necklaces can also be classified as uniform, or graduated. In a uniform strand of pearls, all pearls are classified as the same size, but actually fall in a range. A uniform strand of akoya pearls, for example, will measure within 0.5 mm. So a strand will never be 7 mm, but will be 6.5-7 mm. Freshwater pearls, Tahitian pearls, and South Sea pearls all measure to a full millimeter when considered uniform. A graduated strand of pearls most often has at least 3 mm of differentiation from the ends to the center of the necklace. Popularized in the 1950s by the GIs bringing strands of cultured akoya pearls home from Japan , the graduated style was much more affordable as most pearls in any given strand were small.

Earrings and necklaces can also be classified on the grade of the color of the pearl. While white and more recently black pearls are by far the most popular colors other tinges of color can be found on pearls. Pink, blue, champagne, green and even purple can be found, but to form a complete string of same size and shade pearls can take years. Some colors like purple can only be found in certain types of clams, while other clams can produce a variety of colors if given the right environment.

6.Religious references

According to Rebbenu Bachya , the word Yahalom in the verse Exodus 28:18 means "pearl" and was the stone on the Hoshen representing the tribe of Zebulun. This is extremely disputed among scholars, particularly since the word in question in most manuscripts is actually Yasepheh - the word from which jasper derives; scholars think that refers to green jasper (the rarest and most prized form in early times) rather than red jasper (the most common form). Yahalom is usually translated by the Septuagint as an "onyx", but sometimes as "beryl" or as "jasper"; onyx only started being mined after the Septuagint was written, so the Septuagint's term "onyx" probably does not mean onyx - onyx is originally an Assyrian word meaning ring, and so could refer to anything used for making rings. Yahalom is similar to a Hebrew word meaning hit hard, so some people think that it means diamond. The variation in possibilities of meaning for this sixth stone in the Hoshen is reflected in different translations of the Bible — the King James Version translates the sixth stone as diamond , the New International Version translates it as emerald , and the Vulgate translates it as jaspis — meaning jasper. There is a wide range of views among traditional sources about which tribe the stone refers to.

In a Christian New Testament parable, Jesus compared the Kingdom of Heaven to a "pearl of great price" in Matthew 13: 45-46. "Again, the kingdom of heaven is like unto a merchant man, seeking goodly pearls: Who, when he had found one pearl of great price, went and sold all that he had, and bought it."

The language of symbolism was in common use around the time of Jesus Christ and most people knew this language. The Circle is a symbol of God, it has no beginning and no end. The circle or pearl was considered to represent Love, Knowledge (the combination of equal amounts of Love and Knowledge is a symbol of Wisdom, the 2 circles intertwined (owl eyes) is symbolic of Wisdom. Some other pearls are Truth, and Faith.

The Pearl of Great Price is a book of scripture in The Church of Jesus Christ of Latter-day Saints .

The twelve gates of the New Jerusalem are reportedly each made of a single pearl in Revelation 21:21, that is, the Pearly Gates . "And the twelve gates were twelve pearls; every several gate was of one pearl: and the street of the city was pure gold, as it were transparent glass."

Pearls are compared to holy things, in Matthew 7: 6. "Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you."

Pearls are also found in numerous references showing the wickedness and pride of a people, as in Revelations 18: 16. "And saying, Alas, alas, that great city, that was clothed in fine linen, and purple, and scarlet, and decked with gold, and precious stones, and pearls!"

The metaphor of a pearl appears in the longer Hymn of the Pearl , a poem respected for its high literary quality, and use of layered theological metaphor, found within one of the texts of Gnosticism .

Islamic references

In Islam, the Koran often mentions that dwellers of paradise will be adorned with pearls:

22:23 God will admit those who believe and work righteous deeds, to Gardens beneath which rivers flow: they shall be adorned therein with bracelets of gold and pearls; and their garments there will be of silk.

35:33 Gardens of Eternity will they enter: therein will they be adorned with bracelets of gold and pearls; and their garments there will be of silk.

The Quran describes the wives of the people of Paradise as having eyes that are similar to pearls:

56:22-23 And [there will be] Houris with wide lovely eyes [as wives for the pious], Like unto preserved pearls.

The handsome young boys in paradise are similarly depicted:

52:24 Round about them will serve, [devoted] to them, youths [handsome] as Pearls well- guarded.

Hindu astrological belief in natural pearls

The Vedic tradition describes the sacred Nine Pearls which were first documented in the Garuda Purana, one of the books of the Hindu holy text Atharvaveda. Ayurveda contains references to pearl powder as a stimulant of digestion and to treat mental ailments. According to Marco Polo the kings of Malabar (now known as the Coromandel Coast) wore a necklace of 104 rubies and 104 precious pearls which was given from one generation of kings to the next. The reason was that every king had to say 104 prayers to his "idols" every morning and every evening. At least until the beginning of the 20th century it was a Hindu custom to present a completely new, undrilled pearl and pierce it during the ceremony. Ruby Author Ganesh

Ruby

Ruby crystal before faceting, length 0.8 inches (2 cm) General Category Mineral variety aluminium oxide with chromium , Chemical formula Al 2O3::Cr Identification Color Red, may be brownish or purplish Varies with locality. Terminated Crystal habit tabular hexagonal prisms. Crystal system Trigonal Cleavage No true cleavage Fracture Uneven or conchoidal Mohs Scale hardness 9.0 Luster Vitreous Refractive index ~1.762-1.770 Pleochroism Orangey Red, Purplish Red Ultraviolet fluorescence red under longwave Streak White Specific gravity 4.0 Melting point 2050°C Fusibility perfectly Solubility None Diaphaneity transparent

Ruby is a pink to blood red gemstone , a variety of the mineral corundum (aluminium oxide). The common red color is caused mainly by the element chromium. Its name comes from ruber , Latin for red. Other varieties of gem-quality corundum are called sapphires. It is considered one of the four precious stones, together with the sapphire, the emerald and the diamond. Improvements used include color alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them.

Prices of rubies are primarily determined by color (the brightest and best "red" called Pigeon Blood Red, command a huge premium over other rubies of similar quality). After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions will indicate the stone has been treated one way or another. Cut and carat (size) also determine the price.

Contents

• 1 Physical properties • 2 Treatments and enhancements • 3 Synthetic and imitation rubies • 4 Records • 5 Historical and cultural references • 6 Valley of Rubies

1.Physical properties

Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness . Among the natural gems only diamond is harder, with a Mohs 10.0 by definition.

All natural rubies have imperfections in them, including color impurities and inclusions of rutile needles known as "silk". Gemologists use these needle inclusions found in natural rubies to distinguish them from synthetics, simulants, or substitutes. Usually the rough stone is heated before cutting. Almost all rubies today are treated in some form, with heat treatment being the most common practice. However, rubies that are completely untreated are still of excellent quality and command a large premium.

Some rubies show a 3-point or 6-point asterism or star . These rubies are cut into cabochons to display the effect properly. Asterisms are best visible with a single-light source, and move across the stone as the light moves or the stone is rotated. Such effects occur when light is reflected off the silk (the structurally oriented rutile needle. inclusions) in a certain way. This is one example where inclusions increase the value of a gemstone. Rubies can furthermore show color changes — though this occurs very rarely — and chatoyancy.

2.Treatments and enhancements

Improving the quality of gemstones by treating them is common yet time-consuming practice. Some treatments are used in almost all cases and are therefore considered "acceptable" practices. The most common treatment is using heat. Most if not all rubies at the lower end of the market are heat treated. Heat treatment is performed on the rough stones to improve color, remove purple tingle , blue patches and silk.

These heat treatments typically occur around temperatures of 1800°C (3300°F). Some rubies undergo a process of low tube heat, when the stone is heated over charcoal of a temperature of about 1300°C (2400°F) for 20 to 30 minutes. The silk is only partially broken as the color is improved.

A less acceptable treatment, and one which has gained notoriety in recent years is "Lead Glass Filling" of Rubies. By filling the fractures inside the ruby with lead glass the transparency of the stone is dramatically improved making previously unsuited rubies now fit for applications in jewelry. The process is typically done in 4 steps:

1. The rough stones are pre-polished to eradicate all surface impurities that may affect the process 2. The rough is cleaned with hydrogen fluoride 3. The first heating process whereby no fillers are added. The heating process eradicates impurities inside the fractures. Although this can be done at temperatures up to 1400°C (2500°F) it most likely occurs at a temperature of around 900°C (1600°F) since the rutile silk is still intact 4. The second heating process in an electrical oven with different chemical additives. Different solutions and mixes have shown to be successful, however mostly lead- containing glass-powder is used at present. The ruby is dipped into oil, then covered with powder, embedded on a tile and placed in the oven where it is heated at around 900°C (1600°F) for one hour in an oxidizing atmosphere. The orange colored powder transforms upon heating into a transparent to yellow-colored paste, which fills all fractures. After cooling the color of the paste is fully transparent, that dramatically improves the overall transparency of the ruby.

In case a color needs to be added, the glass powder can be "enhanced" with copper or other metal oxides as well as elements such as sodium, calcium, potassium etc.

The second heating process can be repeated three to four times consecutively, even applying different mixtures.

3.Synthetic and imitation rubies

In 1837 Gaudin made the first synthetic rubies by fusing aluminium at a high temperature with a little chromium as a pigment. In 1847 Edelman made white sapphire by fusing alumina in boric acid. In 1877 Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and Auguste Verneuil manufactured artificial ruby by fusing BaF 2 and Al 2O3 with a little Chromium at red heat. In 1903 Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process.

Other processes in which synthetic rubies can be produced are through the Pulling process , flux process, and the hydrothermal process . Most synthetic rubies originate from flame fusion, due to the low costs involved. Synthetic rubies may have no imperfections visible to the naked eye but magnification may reveal curves striae and gas bubbles. The fewer the number and the less obvious the imperfections, the more valuable the ruby is; unless there are no imperfections (i.e., a "perfect" ruby), in which case it will be suspected of being artificial. Dopants are added to some manufactured rubies so they can be identified as synthetic, but most need gemmological testing to determine their origin.

Imitation rubies have also been present in the gemstone market for some time. Red spinel, red garnet and even glass have been falsely named as rubies. Imitations go back to Roman times and already in the 17th century techniques were developed to color foil red -- by burning scarlet wool in the bottom part of the furnace -- which was then placed under the imitation stone.Trade terms such as balas ruby for red spinel and rubellite for red tourmaline can mislead unsuspecting buyers. Such terms are therefore discouraged from being used by many gemological associations such as the Gemological Institute of America (GIA).

4.Records

Although pieces of red corundum can be found weighing many kilograms, they are generally not of sufficient quality to be valuable as gemstones. For this reason, auction prices are the best indicator of a stone's true value, and prices do not necessarily correlate with size. As of 2006, the record price paid at auction for a single stone was $5,860,000 for an unnamed 38.12 carat cabochon-cut ruby.

5.Historical and cultural references

• According to Rebbenu Bachya , and the New International Version , the word odem means "ruby" in the verse Exodus 28:17 (referring to a stone on the Hoshen), and was the stone representing the tribe of Reuben. Modern Hebrew has taken this meaning. However, odem actually means earth , and is cognate with Adam ; in the Middle East, the earth it refers to is certainly reddish, but the Septuagint translates the term as Sard (which also means red), which is also the name of a common, somewhat opaque, gem. Scholars think the stone intended is probably a Sard, as does the King James Version, scholars think that if not a Sard it may possibly be the related gem carnelian; it is thought possible that Sard and Odem here just mean the colour of the stone, and red Jasper would therefore also be a possibility. • Ruby is the most commonly named precious stone in English translations of the Bible; an example being Proverbs 31: " A virtuous wife is worth more than rubies. ". The underlying masoretic text doesn't necessarily refer to rubies, however. Not only are there issues such as that mentioned with odem , but in the case of Proverbs 31, the masoretic text merely states jewels , and the Septuagint makes Proverbs 31 refer to precious stones ( estin lithon ); some English versions of the bible believe that pearls is a better translation here. • An early recorded note of the transport and trading of rubies arises in the literature on the North Silk Road of China, where in about 100 BC rubies were carried along this ancient trackway moving westward from China. • The famous lighted " Red Stars " mounted above Kremlin spires, thought to be giant rubies mined in Siberia, are colored glass. • Ruby is the birthstone associated with July and of the zodiac sign Leo and Cancer. • Ruby is associated with the Sun in Vedic astrology . • Ruby is associated with a 40th wedding anniversary . • Rubies have always been held in high esteem in Asian countries. They were used to ornament armor, scabbards, and harnesses of noblemen in India and China. Rubies were laid beneath the foundation of buildings to secure good fortune to the structure.

6.Valley of Rubies

Of the world's rubies, 90% currently derive from Myanmar (Burma) whose red stones are prized for their purity and hue. Thailand buys the majority of Myanmar's gems. Myanmar's "Valley of Rubies ", the mountainous Mogok area, 200 km (125 miles) north of Mandalay, is noted for its rare pigeon's blood rubies and blue sapphires. But working conditions in the mines are horrendous. Debbie Stothard of the Alternative ASEAN Network on Burma stated that mining operators used drugs on employees to improve productivity, with needles shared, raising the risk of HIV infection: " These rubies are red with the blood of young people ." Brian Leber (41-year-old jeweler who founded The Jewellers' Burma Relief Project) stated that: " For the time being, Burmese gems should not be something to be proud of. They should be an object of revulsion. It's the only country where one obtains really top quality rubies, but I stopped dealing in them. I don't want to be part of a nation's misery. If someone asks for a ruby now I show them a nice pink sapphire ." In 2007, following the crackdown on pro-democracy protests in Myanmar, human rights organizations, gem dealers, and US First Lady Laura Bush called for a boycott of a Myanmar gem auction held thrice yearly, arguing that the sale of the stones profits the dictatorial regime in that country.

Sapphire Author Ganesh

General Category Mineral Variety

Chemical formula aluminum oxide , Al 2O3 Identification Color Every color except red (which is ruby ) Crystal habit massive and granular Crystal system Trigonal Cleavage None Fracture Conchoidal, splintery Mohs Scale hardness 9.0 Luster Vitreous Refractive index 1.762-1.778 Pleochroism Strong Streak White Specific gravity 3.95-4.03 Fusibility infusible Solubility insoluble Other Characteristics Coefficient of thermal expansion 5e-6–6.6e-6/K

Sapphire refers to gem varieties of the mineral corundum , an aluminum oxide (Al 2O3), when it is a color other than red. Sapphire can be found naturally or manufactured in large crystal boules. Sapphire is used in many applications because of its remarkable hardness including infrared optical components, watch faces, high-durability windows, and wafers for the deposition of semiconductors such as GaN nanorods.

The mineral corundum consists of pure aluminum oxide. Trace amounts of other elements such as iron , titanium and chromium give corundum their blue, yellow, pink, purple, orange or greenish color. Sapphire includes any gemstone quality varieties of the mineral corundum except the fully saturated red variety, which is instead known as ruby, and the pinkish- orange variety known as padparadscha.

Contents

• 1 Natural sapphire o 1.1 Blue sapphire o 1.2 Fancy color sapphire o 1.3 Color change sapphire o 1.4 Star sapphire o 1.5 Treatments o 1.6 Mining • 2 Synthetic sapphire • 3 Historical and cultural references

1.Natural sapphire

Sapphires and rubies are formed at great depth in the earth mantle or the lowest part of the crust. Although blue is considered the normal color for sapphires, they can be found across a full range of spectral colors as well as brown, colorless, grey and black. Those other than blue in color are considered fancy color sapphires. Some natural sapphires can be found as completely transparent, or "white." White sapphires usually come out of the ground as light grey or brown and are then heated to make them clear. However, in very rare circumstances they will be found in a clear state.

Blue sapphire

The 422.99-carat Logan sapphire , National Museum of Natural History , Washington D.C. It is one of the largest faceted gem-quality blue sapphires in the world.

Various shades of blue [dark and light] result from titanium and iron substitutions in the aluminum oxide crystal lattice. Some stones are not well saturated and show tones of grey. It is common practice to bake natural sapphires to improve or enhance color. This is usually done by heating the sapphires to temperatures of up to 1800 °C for several hours, or by heating in a nitrogen deficient atmosphere oven for seven days or more. On magnification, the silk due to included rutile needles are often visible. If the needles are unbroken, then the stone was not heated; if the silk is not visible then the stone was heated adequately. If the silk is partially broken, then a process known as low tube heat may have been used. Low tube heat is the process whereby the rough stone is heated to 1300 °C over charcoal for 20 to 30 minutes. This removes grey or brown in the stone and improves color saturation.

Fancy color sapphire

Purple sapphires are lower in price than blue ones. These stones contain the trace element vanadium and come in a variety of shades. Yellow and green sapphires have traces of iron that gives them their color. Pink sapphires have a trace of the element chromium and the deeper the color pink the higher their monetary value as long as the color is going toward the red of rubies. Sapphires also occur in shades of orange and brown, and colorless sapphires are sometimes used as diamond substitutes in jewelry. Salmon-color padparadscha sapphires often fetch higher prices than many of even the finest blue sapphires. The word 'padparadscha' is Sinhalese for 'lotus flower'. Recently many sapphires of this color have appeared on the market as a result of a new treatment method called "bulk diffusion".

Color change sapphire

Color shift sapphires are blue in outdoor light and purple under [incandescent] indoor light. Color changes may also be pink in daylight to greenish under fluorescent light. Some stones shift color well and others only partially, in that some stones go from blue to bluish purple. Such color-change sapphires are widely sold as “lab” or “synthetic” alexandrite, which is accurately called an alexandrite simulant (also called alexandrium) since the latter is actually a type of chrysoberyl---an entirely different substance whose pleochroism is different and much more pronounced than color-change corundum (sapphire).

Star sapphire

The 182 carat (36.4 g) Star of Bombay, housed in the National Museum of Natural History, Washington D.C., is a good example of a blue star sapphire.

A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism. Star sapphires contain intersecting needle-like inclusions (often the mineral rutile, a mineral composed primarily of titanium dioxide ) that cause the appearance of a six-rayed 'star'-shaped pattern when viewed with a single overhead light source.

The value of a star sapphire depends not only on the carat weight of the stone but also the body color, visibility and intensity of the asterism.

Treatments

Some sapphires are heat-treated or otherwise enhanced to improve their appearance and color, though some people object to such practices and prefer natural untreated stones. Heat treatments tend to improve the sapphire's color and clarity, and it is unusual to find un-heated stones for sale. Diffusion treatments are somewhat more controversial as they are used to add elements to the sapphire for the purpose of improving colors.

Mining

Sapphires are mined from alluvial deposits or from primary underground workings. The finest specimens are mined in Sri Lanka; both the Logan sapphire and the Star of Bombay originate from Sri Lankan mines. Sapphires are also mined in Australia, Madagascar, Thailand and Myanmar. Madagascar leads the world in sapphire production (as of 2007) specifically in and around the city of Ilakala. Prior to Ilakala, Australia was the largest producer of sapphires (as of 1987). Ilakala is prone to violence, but sapphires are found everywhere including on the ground and in the river mud. Pakistan, Afghanistan, India, Tanzania and Kenya also produce sapphires. The US state of Montana has produced sapphires from both the El Dorado Bar and Spokane Bar deposit near Helena. Well-known for their intense, pure blue color, yogo sapphires are found in Yogo Gulch, near Utica, Montana. Gem grade sapphires and rubies are also found in and around Franklin, North Carolina, USA. Several mines are open to the public.

2.Synthetic sapphire

A synthetic star sapphire in a silver ring.

Synthetic sapphire crystals can be grown in cylindrical crystal boules of large size, up to many inches in diameter. As well as gemstone applications there are many other uses:

The first ever laser produced was based on the ruby , the red variety of corundum. While this laser has few applications, the Ti-sapphire laser is popular due to the relatively rare ability to tune the laser wavelength in the red-to-near infrared region of the electromagnetic spectrum.

It can also be easily modelocked. In these lasers, a synthetically produced sapphire crystal with chromium or titanium impurities is irradiated with intense light from a special lamp, or another laser, to create stimulated emission.

Pure sapphire boules can be sliced into wafers and polished to form transparent crystal slices. Such slices are used as watch faces in high quality watches, as the material's exceptional hardness makes the face resistant to scratching. Since sapphire ranks a 9 on the Mohs Scale, owners of such watches should still be careful to avoid exposure to diamond jewelry, and should avoid striking their watches against artificial stone and simulated stone surfaces. Such surfaces often contain materials including silicon carbide, which, like diamond, are harder than sapphire and thus capable of causing scratches (Scheel 2003).

Sapphire is highly transparent at wavelengths of light between 170 nm to 5.3 µm, as well as being five times stronger than glass. This leads to use of synthetic sapphire windows in high pressure chambers for spectroscopy.

Wafers of single crystal sapphire are also used in the semiconductor industry as a substrate for the growth of gallium nitride based devices.

Cermax xenon arc lamp with synthetic sapphire output window

One type of xenon arc lamp known as Cermax (original brand name - generically known as a ceramic body xenon lamp) use sapphire output windows that are doped with various other elements to tune their emission. In some cases, the UV emitted from the lamp during operation causes a blue glow from the window after the lamp is turned off. It is approximately the same color as Cherenkov radiation but is caused by simple phosphorescence.

3.Historical and cultural references

• According to Rebbenu Bachya, and many English Bible translations, the word Sapir in the verse Exodus 28:18 means Sapphire and was the stone on the Ephod representing the tribe of Issachar. • However, this is extremely disputed as though it is true that the English word sapphire derives from the Hebrew sapir (via Greek sapphiros), Sapphires were actually not really known about before the Roman Empire (and were initially considered to be forms of jacinth, rather than deserving of a word to themselves), and prior to that time sapphiros referred to blue gems in general. It is thought by scholars that the sapphire of the Bible was actually lapis lazuli - which was frequently sent as a gift between middle-eastern nations in Biblical times (Texas Natural Science Center, 2006). There is a wide range of views among traditional sources about which tribe the stone refers to. • Blue sapphire is associated with Saturn (Wojtilla, 1973), yellow sapphire with Jupiter in Vedic astrology. It is understood that word Sapphire seems to be a corrupted form of Sanipriya (Sanskrit:- Sani = Saturn, Priya = Beloved). Buddhist monks who moved to Middle East introduced the Stone as Sani piriya and eventually become sapir and sapphire . • Sapphire is the birthstone associated with September.

• The 45th wedding anniversary is known as the sapphire anniversary. • Sapphires are one of the four most valued stones. The other highly valued stones are rubies (sapphires that are red, caused by chromium impurities), emeralds, and diamonds.

• Sapphire City is the capital of the Munchkin Country in The Giant Horse of Oz .

Tanzanite Author Ganesh

Tanzanite

Tanzanite gemstone, featuring an oval mixed cut General Category Mineral Variety

Chemical formula (Ca 2Al 3(SiO 4)(Si 2O7)O(OH) Identification Color Purple to Blue Crystals flattened in an acicular Crystal habit manner, may be fibrously curved Crystal system Orthorhombic Cleavage Perfect {010} imperfect {100} Fracture Uneven to conchoidal Mohs Scale hardness 6.5 Vitreous, pearly on cleavage Luster surfaces Refractive index 1.69-1.70 Optical Properties biaxial positive Birefringence 0.006-0.018 Present, dichroism or trichroism Pleochroism depending on color. Streak White or colorless Specific gravity 3.10-3.38

Tanzanite is the blue/purple variety of the mineral zoisite discovered in the Meralani Hills of northern Tanzania in 1967, near the city of Arusha. It is a popular and valuable gemstone when cut, although its durability is somewhat lacking; its tendency to break sometimes precludes appropriate use as a ring stone.

Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet, and sage-green depending on crystal orientation. However most tanzanite is subjected to artificial heat treatment to improve its colour, and this significantly subdues its trichroism.

Contents

• 1 Commercial history o 1.1 Introduction o 1.2 False media claims damage the Tanzanite industry o 1.3 Recent developments • 2 Prices • 3 Grading • 4 Simulants

1.Commercial history

Introduction

Manuel de Souza, a Goan tailor and part-time gold prospector living in Arusha (Tanzania), found transparent fragments of vivid blue and blue-purple gem crystals on a ridge near Mererani, some 40 km southeast of Arusha. He decided that the mineral was olivine (peridot) but quickly realized that it was not, so he took to calling it "dumortierite", a blue non-gem mineral. Shortly thereafter, de Souza showed the stones to John Saul, a Nairobi - based consulting geologist and gemstone wholesaler who was then mining aquamarine in the region around Mount Kenya. Saul, with a Ph.D. from M.I.T., who later discovered the famous ruby deposits in the Tsavo area of Kenya, eliminated dumortierite and cordierite as possible I.D.s and sent samples to his father, Hyman Saul, vice president at Saks Fifth Avenue in New York. Hyman Saul brought the samples across the street to the Gemological Institute of America who correctly identified the new gem as a variety of the mineral zoisite. Correct identification was also made by mineralogists at Harvard, the British Museum and Heidelberg University, but the very first person to get the identification right was Ian McCloud, a Tanzanian government geologist based in Dodoma. Hyman Saul got two of the samples facetted and showed them to Henry Platt of Tiffany and Company, who immediately appreciated the beauty of the gem and subsequently coined the name "tanzanite", an obvious allusion to its country of origin. These two stones were subsequently mounted in rings. The allusion to the country was thought necessary in order to make the stone marketable to the public: the name has since stuck as a varietal designation.

False media claims damage the Tanzanite industry

On November 16 , 2001 , in the wake of the September 11, 2001 attacks, a front-page Wall Street Journal (WSJ) article by Daniel Pearl and Robert Block alleged that significant al- Qaeda funding was generated through illicit trade in tanzanite. "According to miners and local residents, Muslim extremists loyal to bin Laden buy stones from miners and middlemen, smuggling them out of Tanzania to free-trade havens such as Dubai and Hong Kong." The Tanzanian Mineral Dealers Association insisted there was no connection between al-Qaeda and their industry, while a Tanzanian government investigator insisted there was a connection.

The article suggested that as much as 90% of tanzinite was thought to be smuggled out of the country. The smuggling problem charges were not new; a 1990 New York Times article reported that "Economists say much of the country's bountiful natural wealth – gold, rubies, tanzanite – is smuggled across the border into Kenya with the collusion of Government officials...."

While the story was quickly denounced by many tanzanite dealers as "illogical" and "laughable," information from the story was widely reported in other media sources. Michael Nunn, president of South African gem company and leading tanzanite mining firm Afgem , dismissed WSJ's article as an unsubstantiated "sleazy report."

Both some previous and later U.S. investigations showed that Wadih El-Hage , thought to be a senior aide to Osama bin Laden , moved to Kenya in 1994, where he founded a business called Tanzanite King and helped to run Kenya's al-Qaeda cell. The cell was activated in 1997, and on August 7, 1998 blew up the American Embassy in Nairobi, killing more than 200 people.

Following the WSJ's story of al-Qaeda's involvement with tanzanite, Tiffany & Co., Zale Corp. , QVC , and Walmart which combined make up the world's largest market for tanzanite, halted tanzanite sales. Tanzanian officials reported a 70% decline in industry and miner earnings. In February 2002, at a tanzanite dealer summit, a U.S. State Department said the U.S. had no evidence of current al-Qaeda funding through tanzanite sales, and Tanzanian officials announced police sweeps to remove illegal miners, and a plan to track gems from miners to traders to retailers. As confidence was restored, Zale announced a resumption of tanzanite sales in May, 2002, and was gradually followed by other marketers.

Recent developments

In mid-2002, efforts were begun to include tanzinite as an approved birthstone by U.S. gem associations. By October 2002 the AGTA.org made the first change in more than 90 years to the "modern birthstone chart" and crowned Tanzanite as the December birthstone. Most organizations do not recognize tanzanite as a December birthstone, however, and the AGTA's move to make it a December birthstone has generally been viewed as a marketing ploy.

Natural tanzanite cut and set into a bracelet.

In June 2003, the Tanzanian government introduced legislation banning the export of unprocessed tanzanite to India (like many gemstones, most tanzanite is cut in Jaipur ). The ban has been rationalized as an attempt to spur development of local processing facilities, thereby boosting the economy and recouping profits. This ban was phased in over the next two years, until which time only stones over 0.5 grams were affected.

This is a serious situation for the city of Jaipur, as one-third of its annual gem exports are of tanzanite. Some members of the industry fear the ban will set a precedent, leading Tanzania to ban the export of all raw gem material, including the country's production of tsavorite , diamond and ruby.

In April 2005, a company called TanzaniteOne Ltd. publicly announced that they had taken control of the portion of the tanzanite deposit known as "C-Block" (the main deposit is divided into 5 blocks). Over the next year, this company established a De Beers -like control over the tanzanite market, restricting distribution to a handful of processors referred to as "SightHolders" The company is also increasing its control of all newly mined tanzanite by purchasing a large portion of the production coming from the operations of the independent miners working in the area. This is the first time that a colored gemstone has been controlled in this way. Prices for rough on the open market have increased steadily for the last several years as the company has solidified its control of the market. In August 2005, the largest tanzanite crystal was found in the C-Block mine. The crystal weighs 16,839 carats (3.4 kg) and measures 22 cm by 8 cm by 7 cm.

The mining of tanzanite nets the Tanzanian government approximately USD $20 million annually, the finished gems later being sold mostly on the US market for sales totaling approximately USD $500 million annually.

A rough sample of tanzanite.

2.Prices

The prices of Tanzanite have historically been volatile but TanzaniteOne's SightHolder system is keeping prices firm. Wholesale prices for top quality tanzanite gems were just $225 per carat in the year 2000, to $3500 to $5000 per carat in late 2007.

3.Grading

There is as yet no universally accepted method of grading for tanzanite. TanzaniteOne has introduced plans to remedy "price distortion". The company, formerly called Afgem, has established the nonprofit Tanzanite Foundation, which has developed a quality-grading system that justifies a wider range of prices.

The new system's color-grading scales divide tanzanite colors into two different hues, blue violet and violet blue.

Each has 10 saturation levels :

1 - Vivid Exceptional. 2 - Vivid 1. 3 - Vivid 2. 4 - Intense 1. 5 - Intense 2. 6 - Fancy 1. 7 - Fancy 2. 8 - Light 1. 9 - Light 2. 10 - Pale.

This grading system is not as yet accepted throughout the trade. The world's most prestigious laboratory, the GIA, still uses a different system. The world's most recognised laboratories have yet to reach consensus on terms used for grading tanzanite although the top gradings on most systems will be similar.

4.Simulants

A lab-created simulant of tanzanite is called tanzanique . It closely mimics the color of natural tanzanite however it does not display the same pleochroism . Tanzanite is the mineral zoisite , while tanzanique is fosterite. A periwinkle blue/lavender colored cubic zirconia has also recently come into general use as a tanzanite simulant.

Topaz Author Ganesh

Topaz

a group of topaz crystals on matrix General Category Silicate mineral

Chemical formula Al 2SiO 4(F,OH) 2 Identification Clear (if no impurities), blue, brown, orange, Color gray, yellow, green, pink and reddish pink. Crystal system orthorhombic Fracture conchoidal Mohs Scale hardness 8 Luster Vitreous/glossy Specific gravity 3.4–3.6

Topaz is a silicate mineral of aluminium and fluorine with the chemical formula

Al 2SiO 4(F,OH) 2. It crystallizes in the orthorhombic group and its crystals are mostly prismatic terminated by pyramidal and other faces, the basal pinacoid often being present.

It has an easy and perfect basal cleavage, meaning that gemstones or other fine specimens have to be handled with care to avoid developing cleavage flaws. The fracture is conchoidal to uneven. Topaz has a hardness of 8, a specific gravity of 3.4–3.6, and a vitreous luster. Pure topaz is transparent but is usually tinted by impurities; typical topaz is wine or straw- yellow. They may be made white, gray, green, blue, pink or reddish-yellow and transparent or translucent.

Contents

• 1 Treatments • 2 Localities and occurrence • 3 Etymology and historical and mythical usage

1.Treatments

When heated, yellow topaz often becomes reddish-pink. The color change upon heating was first discovered by a Parisian jeweler around 1750. In particular the yellow Topaz of Brazil has been known to be treated frequently, by wrapping Topaz in Asbestos . Only stones of a brown-yellow color yield the pink; the pale yellow ones usually turn white. The pink color is stable. Topaz can also be irradiated, turning the stone blue, ranging from a light pure color to very dark almost electric blue. A recent trend in jewelry is the manufacture of topaz specimens that display iridescent colors, by applying a thin layer of titanium oxide via physical vapor deposition, this stone is then sold as 'mystic topaz'.

2.Localities and occurrence

Topaz is commonly associated with silicic igneous rocks of the granite and rhyolite type. It typically crystallizes in granitic pegmatites or in vapor cavities in rhyolite lava flows like those at Topaz Mountain in western Utah. It may be found with fluorite and cassiterite. It can be found in the Ural and Ilmen mountains, Afghanistan, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico, and the United States.

Topaz crystals from Brazilian pegmatites are up to 80 cm x 60 cm x 60 cm in size. The biggest topaz crystal ever found, named "El Dorado", was found in Brazil in 1984. It weighs 6.2 kg and belongs to the British Royal Collection. The famous Braganza diamond is in most likelihood a Topaz. The Topaz of Aurungzebe, observed by Jean Baptiste Tavernier measured 157.75 carats.

3.Etymology and historical and mythical usage

Colorless topaz, Minas Gerais, Brazil

The name "topaz" is derived from the Greek Τοπάζιος (Τοpáziοs), which was the ancient name of St. John's Island in the Red Sea which was difficult to find and from which a yellow stone (now believed to be chrysolite: yellowish olivine) was mined in ancient times; topaz itself (rather than topazios ) wasn't really known about before the classical era.In the Middle Ages the name topaz was used to refer to any yellow gemstone, but now the name is only properly applied to the silicate described above.

Many modern English translations of the Bible, including the King James Version mention topaz in Exodus 28:17 in reference to a stone in the Hoshen: "And thou shalt set in it settings of stones, even four rows of stones: the first row shall be a sardius, a topaz, and a carbuncle: this shall be the first row." However, since these translations as topaz all derive from the Septuagint translation tòpazi[òs] , which as mentioned above referred to a yellow stone that wasn't topaz, probably chrysolite, it should be borne in mind that topaz is not meant here.The masoretic text (the Hebrew on which most modern bible translations of the Old Testament are based) has pitdah as the gem the stone is made from; pitdah is of unknown meaning, though scholars think it is related to an Assyrian word meaning flashed . There is a wide range of views among traditional sources about which tribe of the Israelites the stone refers to.

Yellow topaz is the traditional November birthstone, and the state gemstone for the US State of Utah.