Da Wikipedia, l'enciclopedia libera.
Lo smeraldo è una varietà del berillo caratterizzata da un intenso colore verde dovuto probabilmente alla presenza di cromo (fino al 0,19%) e/o di vanadio. Ha la lucentezza di tipo vitreo e presenta lieve pleocroismo, con ω verde e ε verde-azzurro.
Nel Buddhismo è considerato uno dei sette tesori e equiparato alla saggezza. La parola "smeraldo" deriva dal latino smaragdus, proveniente dal greco smaragdos e la sua fonte originaria è un termine semitico, izmargad oppure un termine sanscrito, maragata, che letteralmente significa "smeraldo" o "verde" .
* 1 Abito cristallino
* 2 Colore
o 2.1 Integrità
* 3 Origine
* 4 Giacitura
* 5 Note
* 6 Voci correlate
o 6.1 Altri siti
* 7 Altri progetti
FONTE IMMAGINE: http://it.wikipedia.org/wiki/File:%C3%89meraude_%28Colombie%29.jpg
È di gruppo cristallino dimetrico e sistema esagonale. La sua formula chimica equivale a Be3Al2Si6O18, cioè berillio, alluminio, silicato e ossigeno insieme a cromo. Gli smeraldi sono graduati usando quattro parametri basilari: colore, taglio, integrità e trasparenza. L'aspetto della gemma più importante è sicuramente il colore, seguito dalla trasparenza. Un buon esemplare deve infatti avere non solo una pura tonalità verde, ma anche un elevato grado di trasparenza per essere uno dei migliori al mondo.
Il colore si può suddividere in 3 componenti: tonalità, saturazione e luminosità. I colori giallo e blu, le tonalità che si trovano adiacenti al verde nello spettro, sono i colori secondari che è possibile vedere negli smeraldi. Quello primario è, ovviamente, il verde. Solo le gemme dal colore scuro però, possono essere considerate smeraldi; gli esemplari chiari sono semplicemente berilli verdi. Il grigio è la naturale saturazione visibile in uno smeraldo. Una tonalità grigia di verde è semplicemente un verde opaco.
Gli smeraldi tendono ad avere numerose inclusioni e fessure sulla loro superficie. Diversamente dai diamanti, dove l'integrità è misurata usando una lente con ingrandimento standard 10x, negli smeraldi essa è misurata ad occhio nudo. Così, se uno smeraldo non ha crepe visibili ad occhio nudo, è considerato impeccabile. Pietre che mancano di superficie con delle crepe sono estremamente rare e pertanto quasi tutti gli smeraldi sono "oleati" per migliorare la loro integrità apparente. A causa di questo trattamento non resistono alle temperature estreme. Smeraldi integri ad occhio nudo hanno una tonalità vivida di verde con non più di un 15% di un qualunque colore secondario (o blu o giallo) con una medio-scura tonalità affinché abbiano i prezzi migliori. Questi aspetti non uniformi fanno sì che gli smeraldi siano più simili ad altre gemme nel tagliarli nei cabochon, piuttosto che con sfaccettature.
Di solito la genesi è pegmatica-pnemautolitica . In genere si trova in graniti o rocce metamorfiche (scisti) .
I più antichi giacimenti sono quelli egiziani, vicino alla costa del Mar Rosso nell'Alto Egitto a sud di Kosseir. Quelli degli Urali furono scoperti solo nel 1830 e si trovano nei pressi di Ekaterinburg, dove si trova nei micascisti insieme a fenacite ed acquamarina, così come nella giacitura egiziana. I giacimenti dell'America meridionale furono noti nel '500: i principali (e tutt'ora produttivi) giacimenti sono quelli della Colombia e del Brasile (stati di Goias e Minas Gerais). La miniera più grande al mondo è attualmente quella di Santa Terezina nel Goias dove vengono cavati a cielo aperto. La roccia madre è anche qui uno scisto.
In Europa sono famosi dal medioevo i cristalli dell'Habachtal in Austria. In Italia ottimi campioni (da taglio e grandi fino a 5 cm) sono stati trovati negli anni settanta su alcuni massi abbandonati presso la stazione di Domodossola. In seguito si è trovato un piccolo giacimento (ormai esaurito) nei pressi del Pizzo Marcio.
1. ^ Fernie M.D., W.T. (1906). Precious Stones for Curative Wear. John Wright. & Co.(En)FONTE
From Wikipedia, the free encyclopedia
Emerald is a variety of the mineral beryl (Be3Al2(SiO3)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 toughness (resistance to breakage) is classified as generally poor.
* 1 Etymology
* 2 Properties determining value
o 2.1 Color
o 2.2 Clarity
o 2.3 Treatments
* 3 Emerald localities
* 4 Synthetic emerald
* 5 Emerald in different cultures, and emerald lore
* 6 Notable emeralds
* 7 Gallery
* 8 See also
* 9 References
* 10 Further reading
* 11 External links
The word "Emerald" is derived (via Old French: Esmeraude and Middle English: Emeraude), from Vulgar Latin: Esmaralda/Esmaraldus, a variant of Latin Smaragdus, which originated in Greek: σμάραγδος (smaragdos; "green gem"); its original source being either the Hebrew word אזמרגד izmargad meaning "emerald" or "green" or the Sanskrit word मरग्दम् marakata meaning "green." The name could also be related to the Semitic word baraq (בָּרָק ;البُراق; "lightning" or "shine") (cf. Hebrew: ברקת bareqeth and Arabic: برق barq "lightning"). It is the same source for the names Persian (زمرّد zomorrod), Turkish (zümrüt), Sanskrit (मरग्दम् maragdam), Georgian (ზურმუხტი; zurmukhti), Russian (изумруд; izumrud) and Armenian zmruxt.
Properties determining value
Emeralds, like all colored gemstones, are graded using four basic parameters – the four Cs of Connoisseurship: Color, Cut, Clarity and Crystal. The last C, crystal is simply used as a synonym that begins with C for transparency or what gemologists call diaphaneity. Before the 20th century, jewelers used the term water as in "a gem of the finest water" to express the combination of two qualities, color and crystal. Normally, in the grading of colored gemstones, color is by far the most important criterion. However, in the grading of emerald, crystal is considered a close second. Both are necessary conditions. A fine emerald must possess not only a pure verdant green hue as described below, but also a high degree of transparency to be considered a top gem.
In the 1960s the American jewelry industry changed the definition of 'emerald' to include the green vanadium-bearing beryl as emerald. As a result, vanadium emeralds purchased as emeralds in the United States are not recognized as such in the UK and Europe. In America, the distinction between traditional emeralds and the new vanadium kind is often reflected in the use of terms such as 'Colombian Emerald.'
Scientifically speaking, color is divided into three components: hue, saturation and tone. Yellow and blue, the hues found adjacent to green on the spectral color wheel, are the normal secondary hues found in emerald. Emeralds occur in hues ranging from yellow-green to blue-green. The primary hue must, of course, be green. Only gems that are medium to dark in tone are considered emerald. Light-toned gems are known by the species name, green beryl. In addition, the hue must be bright (vivid). Gray is the normal saturation modifier or mask found in emerald. A grayish green hue is a dull green.
Emerald tends to have numerous inclusions and surface breaking fissures. Unlike diamond, where the loupe standard, i.e. 10X magnification, is used to grade clarity, emerald is graded by eye. Thus, if an emerald has no visible inclusions to the eye (assuming normal visual acuity) it is considered flawless. Stones that lack surface breaking fissures are extremely rare and therefore almost all emeralds are treated, "oiled", to enhance the apparent clarity. Eye-clean stones of a vivid primary green hue (as described above) with no more than 15% of any secondary hue or combination (either blue or yellow) of a medium-dark tone command the highest prices. This relative crystal non-uniformity makes emeralds more likely than other gemstones to be cut into cabochons, rather than faceted shapes.
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. Other liquids, including synthetic oils and polymers with refractive indexes close to that of emerald such as Opticon are also used. The U.S. Federal Trade Commission requires the disclosure of this treatment when a treated emerald is sold. The use of oil is traditional and largely accepted by the gem trade. Other treatments, for example the use of green-tinted oil, are not acceptable in the trade. The laboratory community has recently standardized the language for grading the clarity of emeralds. Gems are graded on a four step scale; none, minor, moderate and highly enhanced. Note that these categories reflect levels of enhancement not clarity. A gem graded none on the enhancement scale may still exhibit visible inclusions. Laboratories tend to apply these criteria differently. Some gem labs consider the mere presence of oil or polymers to constitute enhancement. Others may ignore traces of oil if the presence of the material does not materially improve the look of the gemstone.
Given that the vast majority of all emeralds are treated as described above, and the fact that two stones that appear to be similar in quality may actually be quite far apart in treatment level, a consumer considering a purchase of an expensive emerald is well advised to insist upon a treatment report from a reputable gemological laboratory. All other factors being equal, a high quality emerald with an enhancement level graded moderate should cost 40–50% less than an identical stone graded none.
 Emerald localities
Emeralds in antiquity were mined by the Egyptians and in Pakistan and Austria.
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. Emeralds come from three main emerald mining areas in Colombia: Muzo, Coscuez, and Chivor. Emeralds are also found in other countries, such as Afghanistan, Australia, Austria, Brazil, Bulgaria, Cambodia, Canada, China, Egypt, Ethiopia, France, Germany, India, Italy, Kazakhstan, Madagascar, Mozambique, Namibia, Nigeria, Norway, Pakistan, Russia, Somalia, South Africa, Spain, Switzerland, Tanzania, United States, Zambia and Zimbabwe. In the US, emeralds have been found in Connecticut, Montana, Nevada, North Carolina and South Carolina. In 1998 emeralds were discovered in the Yukon.
 Synthetic emerald
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 was 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, a typical seven-month growth run producing emerald crystals of 7 mm of thickness. Gilson sold his production laboratory to a Japanese firm in the 1980s, but production has ceased since; so did Chatham's, after the San Francisco earthquake in 1989.
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, 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 to prevent nucleation and confine growth to the seed crystals. Growth occurs by a diffusion-reaction process, assisted by convection. The largest producer of hydrothermal emeralds today is Tairus in Russia. They have succeeded to synthesize emeralds that have similar chemical composition as emeralds in alkaline deposits in Colombia, hence they are called “Colombian Created Emeralds” or “Tairus Created Emeralds”. 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.
 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, D.C.
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Gachala_Emerald_3526711557_849c4c7367.jpg
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 Brantôme, who referred to the many impressive emeralds the Spanish under Cortez had brought back to Europe from Latin America. On one of Cortez's most notable emeralds he had the text engraved Inter Natos Mulierum non sur-rexit mayor ("Among those born of woman there hath not arisen a greater"; Man. XI, 11) which referred to John the Baptist. Brantôme considered engraving such a beautiful and simple product of nature sacrilegious and considered this act the cause for Cortez's 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 of France who died soon after.
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.
The Authorized King James Version of the Bible, in Exodus 28:18 and 39:11, lists "emerald" as one of the precious stones in the breastplate of the high priest of the Jews; but modern consensus is that this is probably a mistranslation. (See Hoshen.)
Ireland is often referred to, especially in America, as the "Emerald Isle".
In L. Frank Baum's The Wonderful Wizard of Oz, the city where the wizard rules is made of emerald and is called the Emerald City. The sixth book in the series is named after it.
 Notable emeralds
Chalk Emerald Colombia
Duke of Devonshire Emerald
Mogul Mughal Emerald
Bahia Emerald Brazil
1. ^ a b c "Emerald at Mindat". Mindat.org. 2010-07-19. http://www.mindat.org/min-1375.html. Retrieved 2010-07-30.
2. ^ a b Hurlbut, Cornelius S. Jr, & Kammerling, Robert C., 1991, Gemology, p. 203, John Wiley & Sons, New York ISBN 0471526673
3. ^ Fernie, William Thomas, MD (1907). Precious Stones for Curative Wear; and other remedial uses; likewise the nobler metals. Bristol: John Wright & Co..
4. ^ Harper, Douglas. "emerald". Online Etymology Dictionary. http://www.etymonline.com/index.php?term=emerald.
5. ^ Tavernier, J. B. (1925) Travels in India by Jean Baptiste Tavernier, Baron of Aubonne; translated from the original French edition of 1676 with a biographical sketch of the author, notes, appendices, &c. by V. Ball. 2nd ed., edited by William Crooke; Vol. II, pp. 44, 58
6. ^ a b Wise, R. W. (2001) Secrets of the Gem Trade: the connoisseur's guide to precious gemstones. Brunswick House Press ISBN 0972822380; p. 108
7. ^ Read, Peter (2008) Gemmology 3rd rev. ed. NAG Press; p. 218
8. ^ "Guides for the Jewelry, Precious Metals, and Pewter Industries". Ftc.gov. 1996-05-30. http://www.ftc.gov/bcp/guides/jewel-gd.shtm#%A7%2023.22%20Deception%20as%20to%20gemstones. Retrieved 2010-07-30.
9. ^ Giuliani, G. (2000). "Oxygen Isotopes and Emerald Trade Routes Since Antiquity". Science 287: 631. doi:10.1126/science.287.5453.631. http://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_7/b_fdi_53-54/010020866.pdf.
10. ^ Emerald Mining Areas in Colombia, with location map of these three districts.
11. ^ Nassau, K., 1980, Gems Made By Man, Gemological Institute of America, ISBN 0873110161
12. ^ U.S. Patent 3,567,642
13. ^ U.S. Patent 3,567,643
14. ^ Karl Schmetzer, Dietmar Schwartz, Heinz-Jurgen Bernhardt, Tobias Hager “A new type of Tairus hydrothermally-grown synthetic emerald, colored by vanadium and copper” Journal of Gemmology of Gemmological Association of Great Britain, September, Vol. 30 (1–2) 2006–2007, pp. 59–74
15. ^ Hurlbut, Cornelius S. Jr, & Kammerling, Robert C., 1991, Gemology, p. 81, John Wiley & Sons, New York ISBN 0471526673
16. ^ "Guides for the Jewelry, Precious Metals, and Pewter Industries". Ftc.gov. 1996-05-30. http://www.ftc.gov/bcp/guides/jewel-gd.htm. Retrieved 2010-07-30.
17. ^ Kunz, George Frederick (1915). Magic of Jewels and Charms. Philadelphia: Lippincott Company. p. 305. ISBN 0766143228. http://books.google.com/?id=uj8vr0RC_EQC&pg=PA305.
18. ^ "The men of the Emerald Isle" is a phrase in William Drennan's "Erin". Oxford Dictionary of Quotations; 2nd ed. Oxford University Press; 1953; p. 189FONTE:
Ci sarebbe molto da parlare su questa pietra, per esempio che il vaso del Santo Graal, che sappiamo tutti conteneva il sangue di Cristo, fosse intagliato con lo smeraldo sceso dalla fronte di Lucifero, inoltre, questa fantastica pietra ha dato il nome alla Tabula Smeragdina di Ermete Trismegisto, dove si parla della creazione dell’universo. Anche questa viene posta sul pettorale del prete ebraico e tra le pietre dell’Apocalisse che si trovano nelle fondamenta della nuova Gerusalemme.
Il verde dello smeraldo crea quiete e attenzione, aumenta le facoltà celebrali, è la clorofilla che si unisce al sangue rosso dell’essere umano e rappresenta l’energie solari, facendo riposare e rigenerare lo spirito.
Il simbolismo della pietra è la purezza, fedeltà e speranza nell’immortalità, inoltre è legato al segno della vergine ed al Pianeta Venere.
La strega o il magista indosseranno lo smeraldo su di un anello durante le operazioni della mattina.
Fonte: Magia Sperimentale Gian Piero BonaFONTE:
Emerald is a variety of Beryl colored green by inclusions of Chromium. This vivid and beautiful gem is sacred to Venus, Goddess of Love & Fertility, and is the birthstone for the month of May & sign of Taurus.
Beryllium Aluminum Silicate, Be3 Al2 (SiO3)6
Crystal System: Hexagonal
Cleavage: Poor, Basal
Hardness: 7.5 - 8
Refractive Index: 1.576 - 1.582
Birefringence: 0.004 - 0.008
Specific Gravity: 2.70 - 2.78
Emerald (beryllium aluminum silicate) is a variety of the mineral Beryl with a vivid green color caused by Chromium, and occasionally Vanadium inclusions. This exceptionally beautiful crystal has a long history, befitting one of the world's oldest gems. Emerald is formed by traumatic events in the earth's crust (more on this below), and the age of deposits can vary widely - at one end of the scale are African crystals, notably from Zimbabwe, which formed at least 2,600 million years ago and at the other end, Pakistan's relative youngsters are 'just' 9 million years old.
Emerald could be called a freak of nature, or at least of geology. Beryl is naturally colorless, with color variations caused by chemical impurities present while the crystal is forming. Emerald takes its color from chromium and vanadium, but in nature these elements don't form anywhere close to deposits of Beryl, so the only way to make genuine Emerald is to smash the Earth's crust violently enough to throw Chromium, Vanadium and Beryl together, muddle them up, bury the lot and let nature take its course.
This traumatic birth means that Emerald is a highly included gem - almost all natural stones will have scratches, flaws and inclusions to some degree. Large pieces of Emerald crystal are very rare indeed and large fine pieces are more valuable than Diamond by weight. Marks and inclusions that would affect the value of other gems are tolerated in cut Emeralds. Small, fine inclusions don't affect value as much as the intensity of color, and an included dark Emerald will be more valuable than a flawless, pale one. In the gem industry each stone's collection of flaws is endearingly known as its jardin (garden). Gemologists and magic users both share the sentiment that an Emerald's flaws are part of its beauty, adding to its charm like laughter lines on a face.
Emerald can form in a wide range of green and green-blue shades, and generally the greener the stone the more valuable it is. The world's finest come from Columbia, and their exceptional transparency, fire and color set the standards that other Emeralds are judged by. Columbian Emerald has a unique color, a fine, shining green with no hint of blue that is so highly valued that even obvious flaws are acceptable in a cut stone. The country's mines also produce rarities like Trapiche Emeralds (trapiche is a grinding wheel), with a 6-rayed star emanating from the center of the stone that is caused by dark carbon impurities.
Columbia boasts at least 150 deposits, the best known being Muzo and Chivor, both of which have been mining gems since precolumbian times and were a source of Emerald to the Inca. The most commercially important mine, Coscuez, produces about three quarters of the country's supply. Columbia's neighbor Brazil produces fine crystals, with occasional cat's eye and 6-ray stars. Outside South America and Africa, where recent new finds are keeping the market well stocked, Emerald deposits are also found in Madagascar, Pakistan, India, Afghanistan, Australia and Russia.
Emerald, with its rich green color and scintillating sparkle, has always been a very popular and precious gemstone. In the ancient world it was sacred to Goddesses of love and nature, and the Romans record it as the sacred stone of Venus. This tradition continues today, with Emerald still being a favorite stone for love and sex magic. It is believed to be especially useful in spells to encourage faithfulness or bring home a straying lover. If your lover gives you an Emerald as a gift it is said the stone will crack or fade if he or she is ever unfaithful to you.
Emerald is used in sex magic to encourage passion and arousal, overcome shyness and inhibitions and increase fertility. When worn as a talisman it is said to protect against violence, abuse and rape and Emerald is a powerful healing stone for the trauma of such attacks. Emerald also has a special link with the Crone Goddess, and when worn by a woman who has passed the menopause it is said to help her develop her psychic, magical and artistic abilities.
Magically, Emerald also represents time and the astral planes. Most of us have trouble living in the magical moment of 'now' because we are too busy remebering the past or dreaming about the future. Emerald can teach you to focus your attention in the present and live each moment to the fullest. Meditation and magical work with the crystal is believed to help you remember that you can move through time with ease, allowing you to work more effectively on the astral planes, access the Akashic records (the 'imprint' that all living things have made on the Universe through time) and meet with beings that inhabit other worlds.
In ancient Egypt Emerald was sacred to the Goddess Isis and symbolized resurrection. In many cultures it was buried with the dead or placed among their funeral wrappings in order to ensure a safe passage through the other-worlds and a fortunate reincarnation.
Working with Emerald can help enhance your intuitive and prophetic powers, memory, eloquence and communication skills. It is said to develop inner strength and wisdom and help you make the most of your unique skills and talents. As a charm, Emerald is said to draw good things to its bearer, including happiness, friends, good fortune, creativity and energy. Wearing the stone or drinking an Emerald gem elixir will help you get the best results from any psychic or magical work you are performing.FONTE
Propizio per le relazioni affettive, simboleggia la libertà e l’amore assoluto, ha qualità divinatorie, e in passato veniva impiegato per aiutare nella ricerca di oggetti perduti. Rafforza la memoria, e combatte febbre e anemie.