Origin of name
The "El-Dorado Topaz" discovered in Minas Gerais in Brazil, seems to get its
name from the legend of El-Dorado, the city of the legendary golden king of
South America, who at the time of his inauguration to the high office, was
completely covered with gold dust over a layer of sticky mud previously
applied on his naked body and then conveyed on a decorated raft with great
pomp and pageantry to the middle of the deep and sacred lagoon of Guatavita,
where he offered a great heap of gold and emeralds to the demon whom the
Muisca people
worshipped as their God and Lord, by throwing them overboard into the deep
lake, and perhaps also diving into the sacred lake in order cleanse himself
of the mixture of mud and gold. The offering of gold and emeralds to the God
and the dip taken in the sacred waters achieved a spiritual cleansing that
prepared the newly appointed king to the high office he was about to assume.
The legend which originated in the Andes of present-day Colombia in the
1530s enticed European explorers who undertook expeditions in search of the
legendary city for two centuries, but without any success. The most famous
of these expeditions was the one undertaken by Franciso de Orellana and
Gonzalo Pizzaro in 1541, who navigated the Amazon river all the way to its
delta. The Muisca territories eventually fell into the hands of the Spanish,
who realized that in spite of large quantities of gold in the hands of the
Indians, there were no golden cities or gold mines in these territories, as
the legends had suggested. The Muiscans obtained most of their gold by
trade. However the legends refused to die down, as some of the Indians
themselves believed in it, and some of them had in fact witnessed the
Guatavita installation ceremonies.
The name "El-Dorado" today is used metaphorically to denote any place where
wealth could be acquired rapidly. In the United States, the name was given
to El-Dorado County, California, and to various towns and cities in other
states. It has also been used metaphorically to represent something much
sought after, that may sometimes not even exist, or may not ever be found.
The "El-Dorado Topaz" discovered in Minas Gerais, Brazil, seems to have been
named as such, in order to perpetuate the memory of this undying legend that
originated in South America, where the enormous gemstone also originated.
The enormous weight of the rough stone, 37 kg. and the finished gemstone
31,000 carats, has created another legend, as the faceted gemstone has
become the largest ever faceted gemstone in the world.
©
Programa Royal Collections. Agrupación Europea de Interés Económico 2006
Characteristics of the gemstone
The largest faceted topaz and gemstone in the
world
The "El-Dorado" rough topaz discovered in 1984, in Minas Gerais,
Brazil, weighed an astonishing 37 kg. After cutting and polishing the
finished gemstone weighed only 6.2 kg. Thus 30.8 kg of the original rough
stone was lost in the cutting process, equivalent to 83% of the original
weight of the stone. This enormous loss in weight was mainly due to the poor
non gem-quality material that constituted the original rough stone, which had to
be removed compulsorily, in order to arrive at a reasonable product with
good cut, color and clarity. Indeed the removal of a large quantity of the
rough stone was justified, as the final product turned out to be an
exceptional quality faceted topaz, with a perfect cut, color and clarity.
The finished gemstone had a perfect emerald-cut, good clarity and a
desirable yellowish-brown color. The weight of the finished stone was 31,000
carats (6.2 kg), and the stone became the largest faceted topaz as well as
the largest faceted gemstone in the world. This twin distinction was
previously held by the 21,005-carat Brazilian Princess Topaz of the American
Museum of Natural History, New York, and later by the 22,892.5-carat
American Golden Topaz of the Smithsonian's National Museum of Natural
History, in Washington DC, but today they have been pushed to the 4th and
3rd place respectively.
Please click here to view the list of
famous topaz gemstones, greater than 1000 carats in weight, arranged in
descending order of weights.
Why topaz crystals can grow to enormous sizes
?
Topaz is a gemstone that had been known by mankind for well over two
millennia, and had been valued since ancient times, not only for its
ornamental properties, but also for the spiritual, metaphysical, and
medicinal powers the gemstone was purported to have possessed. Chemically
topaz is a silicate, the most abundant mineral found on the earth's surface.
It belongs to a sub-class known as Nesosilicates, having the formula Al2SiO4(F,OH)2,
variously referred to as aluminum fluorosilicate, fluoroaluminum silicate or
aluminum silicate fluoride hydroxide. The topaz crystal consists of chains
of aluminum octahedra, formed by octahedrally co-ordinated aluminum cations
linking together. The aluminum octahedra can be AlO4F2
or AlO4(OH)2. The long chains of
aluminum octahedra are cross linked by the negatively charged silicon-oxygen
tetrahedral units (SiO4)‾
This type of structure is very stable and the chains can grow to enormous
lengths producing giant crystals. Thus topaz is one of the few gem minerals
that can grow into incredible sizes such as the 37 kg El-Dorado rough stone.
An enormous topaz crystal in the AMNH, New York, weighs a whopping 273 kg
equivalent to 600 lbs. Topaz crystallizes in the orthorhombic crystal system
forming long to short vertically striated prismatic crystals terminated by
pyramidal or dome-shaped faces.
The high density, refractive index and
hardness of topaz
The strong bonds and close packing of atoms and ions in the topaz crystal
structure impart a high density, refractive index and hardness to the
gemstones. The specific gravity of topaz is 3.4 to 3.6. The refractive index
varies between 1.61 to 1.63. The chemical formula of topaz is Al2[SiO4](F,OH)2.
The comma between F and OH means that the OH can
replace F or vice versa in the crystal lattice. The more OH there is in the
crystal the higher will be the refractive index and the value will be closer
to the upper range 1.63. If the quantity of F in the crystal is higher the
refractive index will be less and closer to the lower range of 1.61. The
hardness of topaz is 8 on the Mohs scale, which makes it one of the hardest
minerals in nature, and thus suitable for setting in jewelry.
The luster of topaz
The luster of a gemstone is its brilliancy, determined by the amount of
incident light reflected from its surface. The luster of topaz is adamantine
to vitreous, i.e. something between the luster of diamond (adamantine) and
ruby, sapphire and quartz (vitreous). Adamantine means resembling diamond in
luster. Vitreous means resembling glass in luster. The diaphaneity of
topaz which is the quality of being diaphanous or transparency, is
transparent to translucent. In short wave length ultra-violet light topaz
gives a golden-yellow fluorescence and in long wave length ultra-violet
light a cream colored fluorescence. Cleavage is the tendency of crystals,
minerals and rocks to break in preferred directions, known as cleavage
planes, so as to yield more or less smooth surfaces. The cleavage of topaz
is perfect and basal.
The dispersion of topaz
Dispersion is the ability of a gemstone to bend white light separating it
into the colors of the spectrum depending on wavelength of the color of
light. Dispersion is measured in terms of the difference of the refractive
index of the gemstone in violet light and its refractive index in red light,
the two colors at the extreme ends of the visible spectrum. A dispersion
greater than 0.03 is considered as high degree of dispersion. Both diamond
(0.044) and cubic zirconia (0.060) have very high dispersion, and hence
these gemstones have "fire" or "sparkle." The dispersion of ruby and
sapphire is 0.018 much less than 0.03 and as such these stones lack the
sparkle of diamonds. Likewise the dispersion of topaz is only 0.014. The
lack of "fire" in these stones is compensated partly by their good luster,
and an appropriate cut that can increase the dispersion. In rubies the red
fluorescence produced in light rich in u-v rays also contributes towards the
brilliance of the stone.
Pleochroism in topaz
Pleochroism or dichroism is the change in color that can be seen when a
mineral is rotated while being observed in a petrographic microscope under
plane polarized light. Pleochroism manifests itself as a change in color, eg.
blue to red, or a change in the intensity of the color, eg. light blue to
dark blue. Pleochroism is caused by the ability of a mineral to absorb
different wave lengths of transmitted light depending upon its
crystallographic orientations. The color that is observed is usually the
complementary color of the color that is absorbed. Eg. If the wave length of
transmitted light absorbed corresponds to green color, the mineral is seen
as red, because red is the complementary color to green. Likewise if wave
length corresponding to orange is absorbed the mineral will appear
blue, as the complementary color of orange is blue.
Pleochroism depends mainly on the crystallographic nature of the minerals.
Isotropic minerals are always non-pleochroic. Hexagonal, trigonal and
tetragonal minerals are generally always dichroic. Orthorhombic, monoclinic
or triclinic minerals are generally pleochroic.
Topaz, being a orthorhombic mineral should show strong pleochroism, but the
mineral seems to be an exception.
In topaz pleochroism is weak or absent. This property can be used to
distinguish between blue topaz whether natural or treated and aquamarine.
Aquamarine belongs to the hexagonal crystal system and is therefore dichroic.
The dichroism in aquamarine is from blue to greenish-blue or bluish-green.
Color in topaz
The different colors in which topaz can be found are colorless, pale blue,
light green, yellow, yellowish-brown, orange, pink and red. Out of these the
commonest colors are colorless, yellow and yellow-brown. The rarest colors
are pink and red. The colorless variety of topaz is pure topaz without
impurities. The colored varieties of topaz contain trace amounts of
impurities such as iron. But, these impurities do not impart color directly
to topaz. The iron atoms form an unstable species in the crystal, which
absorbs a visible photon of light and jumps to an excited state. When these
excited species returns to the ground state it emits light in different
regions of the visible spectrum, giving rise to the variety of colors given
above. The unstable species formed by iron atoms are known as color centers.
Treated topaz
Natural pink topaz is very rare. There was only one source in the world that
produced fine rich pink crystals, and that source was Katalang in Pakistan.
But, today most of the pink topaz is obtained by subjecting the
brownish-yellow chrome-bearing crystals found at Ouro Petro in Minas Gerais,
to careful heat treatment. The heat-induced pink color is permanent, because
the pink color center produced by heat treatment is stable. Heat treated
pink topaz is also known as Brazilian Ruby.
Another form of treatment applied in topaz is radiation treatment.
Irradiation of colorless and greenish brown crystals can induce a variety of
colors such as smoky-grey, cinnamon-brown, yellow-orange, and blue,
depending on the time of exposure to the radiation. The most commonly used
radiation process is gamma cobalt 60 radiation. Neutron bombardment using a
linear accelerator is less used, and may leave a faint
residual-radioactivity, which however dissipates in a few days.
Greenish-brown crystals exposed to radiation treatment produces the popular
and permanent blue colors not normally found in natural topaz. Such colors
are variously known as "London blue," "Swiss Blue" and "Sky blue." Even
though it may not be possible to detect radiation treatment, it is well
known that intense blue colors in topaz are not found naturally and are
produced only by such treatment. All irradiated topaz gems in the United
States are processed in a special facility in Missouri to ensure that they
conform to strict safety standards. All imported blue topaz are also
subjected to this examination before they are released to the importers.
History of the El-Dorado Topaz
Source of the topaz
The "El-Dorado Topaz" was discovered in the year 1984, in the mineral-rich
southeastern state of Minas Gerais, of Brazil. The state had been the
premier source of enormous topaz crystals in the world. All the gemstones in
the list of 15 famous faceted topaz gemstones greater than 1,000 carats in
weight, originated in Brazil, and invariably from the state of Minas Gerais.
Please click here for the list.
Minas Gerais, the fourth largest state area wise and the second most populous state
in Brazil, had been famous throughout history because of its rich mineral
resources. Minas Gerais in the Portuguese language means "General Mines" a
reference to the gold mines discovered in 1693 and subsequently diamond
mines in the 1720s. Most of the production of these mines eventually ended
up in Lisbon, the capital city of Portugal, and served in no small measure
to boost the riches of the colonial master, helping the country to become
one of the most powerful Imperial Powers in Europe. The exploitation of the
gold mines were so exhaustive and complete that within about 200 years, in
the 19th century, the gold deposits were completely exhausted. During this
period Ouro Petro the capital city of Minas Gerais was one of the booming
capital cities in the whole of America. By the end of the 19th century even
diamond production seriously declined, and South Africa took over as the
world's leading producer of diamonds, with the discovery of kimberlite
diamond pipes in the year 1871.
After Brazil became a republic in the early 20th century, the large deposits
of other minerals and gemstones such as topaz, aquamarine, tourmaline,
kunzite etc. were exploited by the Government, with the help of foreign
participation. Today, Brazil is one of the world's largest producers and
exporters of gemstones, 80 % of which come from the state of Minas Gerais.
In Minas Gerais, Topaz is produced in the 290 sq. km. region running in the
east-west direction, west of Ouro Petro, known as the Topaz belt. Two active
mechanized mines in this belt are the Capāo mines and
the Vermelhão mines. Capāo, which is situated just outside Ouro Petro, about
5 km from the village of Rodrigo Silva, is an open pit mine. Vermelhão, the
second mechanized mine is located about 12 km east of Capão. Besides this
there are also several smaller mines in the region still employing the
traditional techniques such as manual digging and panning. It is not known
exactly in which mines the El-Dorado topaz was discovered.
Processing of the El-Dorado
Topaz
The El-Dorado rough topaz weighed a massive 37 kg when first unearthed in
1984. It is not known where the rough stone was cut and polished, but a good
part of the rough stone had to be eliminated being poor non gem-quality
material. Eventually when the processing was completed only 6.2 kg of the
original rough stone was left, but the finished product turned out to be an
exceptional quality topaz gemstone, with an perfect emerald-cut, good
clarity and transparency, and a beautiful yellowish-brown color. The
El-Dorado also became the largest faceted topaz in the world having a weight
of 31,000 carats
Objectives of the Programa Royal Collections
The Programa Royal Collections is a business grouping launched in the year
1997 in the form
of an European Economic Interest Grouping, regulated by the European Union
and formed of associated bodies with representations in Europe, the
Americas, and Asia. The main objective of the grouping was to build up and
maintain a comprehensive and unique collection of gems and minerals that was
representative of all varieties and classes, and also precious-metal and
gemstone artwork, and then display them to the public or make available for
display to the public on a hire basis, in exhibitions, in order to bring
natural and cultural heritages to a wider audience. The grouping brought
together business institutions specializing in gemology. geology, art, the
management of cultural tourism projects, and international trade and
communication.
The display of a wide variety of rare gemstones and artwork based on
precious metals and gemstones, is a culturally enriching experience for the
people. The aim of the PRC does not end by providing this experience
to the visitors, but continues further in trying to convert these
experiences into a discovering and learning process that goes beyond mere
passive observation.
The El-Dorado Topaz enters the Programa Royal
Collections
Within a short period of its inception, the Programa Royal Collections was
successful in assembling the world's largest collection of gems, with a
total weight of over 500,000 carats, and consisting of thousands of
individual faceted gemstones, from all corners of the world, representing
all classes and varieties of gemstones, some of which were the largest and
most exceptional in their class, that was ever discovered. The
El-Dorado Imperial Topaz, is one such exceptional quality topaz, that became
famous as both the world's largest faceted gemstone and also the world's
largest faceted topaz.
Three main categories of the collection
The collections of the PRC are assembled under three categories :- Precious
Stones, Art, and Natural Sciences.
The Precious Stones Collection consisting of thousands of faceted gemstones,
totaling over 500,000 carats, is said to be the largest collection of gems
in the world.
The Art Collection consists of several exquisitely carved masterpieces of
sculpture from classical to contemporary, using precious metals and
gemstones as the working material, perfected by internationally renowned
artists such as Picasso, Dali and Gaudi. It also includes an original
precious stones art gallery known as "Art & Gems" representing all five
continents.
The Natural Sciences section is devoted to mineralogy and other related
sciences. It includes a representative collection of minerals, bringing
together specimens from all corners of the world.
Educational value of the collections
As pointed out earlier the aim of the PRC sponsored exhibitions
is not only to provide the common people a rich cultural experience,
but also help them to use these experiences to discover and learn more about
gemstones and minerals. The twofold experience of enjoying and learning is
the main philosophy of holing these exhibitions. In the case of gemstones,
every exhibit is accompanied by educational display cases, containing
gemological maps, rough gemstones, cutting and polishing equipment etc. A
wealth of information in respect of the gem variety is provided in different
languages and different levels of specialization, in the form of posters,
information panels, photographs, fact files, brochures, catalogues etc. Thus
visitors are able to discover for themselves all aspects of the gem
industry, starting from the formation of the mineral in the earth's crust,
mining, cutting and polishing, the chemical, physical and optical properties
of gemstones, testing and authentication of gemstones, differences between
original and synthetic gemstones etc. A visitor who had gone through any one
of the tailor made exhibition programs of the PRC, might have acquired
sufficient knowledge to make confident purchases of gemstone jewelry in the
future, without being cheated.
The three categories of gem collections
The Programa Royal Collections contain the world's largest gem holdings
weighing over 500,000 carats. This enormous collection of gems is organized
into three categories.
1) Treasures of the Earth - This is the main collection consisting of 15,000
gems, weighing 250,000 carats, classified according to their classes or
varieties.
2) Special Exhibition Gems - This constitutes a collection of 20 outstanding
gems, brought together mainly for their enormous size and quality. The
collection weighs 117,000 carats. The 31,000-carat El-Dorado Imperial Topaz
belongs to this collection, which also includes several other enormous and
famous gemstones.
3) Single Theme Exhibitions - Single theme collections specializes on a
single class or variety of gems. The names given to some of these
collections are :-
Imperial and Noble - This collection specializes only on topaz, consisting
of 58,000 carats of topaz gemstones of all sizes and colors, such as
colorless, blue, yellow, lilac etc.
Brilliant Rainbow - This is a diamond collection consisting of over 300
carats of diamonds of various colors such as blue, green, yellow, black and
grey etc.
Other single theme exhibitions include "Water Flames" which is a collection
of opals, "Organic Gems"- a collection of gems of organic origin such as
pearls, corals, nacre, ivory, amber etc. "A Universe of Color" - a
collection of tourmalines of all varieties, "Fire Born Gems"- a collection
of garnets of all varieties, and other similar gems like olivine and spinel,
"Princes of the East" - collection of corundum including rubies, blue
sapphires and fancy colored sapphires, "Her Highness the Beryl" - a
collection of beryls such as emeralds, aquamarines, morganite, and goshenite,
and "Everything about the Citrine" - a collection of citrine weighing 50,000
carats.
Hiring of exhibitions to organizations in
countries and cities
The exhibitions of the Programa Royal Collections are given out on hire
under various terms and conditions set by the PRC, to organizations in
different countries and cities, that may desire to hold these exhibitions.
Such exhibitions are tailor-made to suite the requirement of the hosting
organizations, such as available exhibition space, theme requirements,
exhibition style, target audience etc. The PRC's experts also provide
support and advice during the whole exhibition process, beginning from the
designing, transportation, installation, security, promotion and the
formulation of educational programs and catalogues.
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References
1. Website of the Programa Royal Collections
2. Topaz - A Neosilicate - Edna B, Anthony - The New
Mexico Facetor.
3. Gem & Crystal Treasures - Peter Bancroft.
External Links
Website of
Programa Royal Collections
