Origin of name
"Lua de Maraba" in the Portuguese language means "The Moon of Maraba."
Maraba is one of the biggest cities in the State of Para, the second largest
state area wise situated in the northern region of Brazil in the lower
Amazon basin. Maraba, whose
name is derived from the Tupi language, spoken by Tupi Indians of Brazil, is
situated by the Tocantins River one of the three main tributaries that join
the mighty Amazon River on its right bank before it joins the Atlantic. The
Tocantins from Maraba downstream is fairly navigable, and therefore a new
river port has been constructed at Maraba mainly for the use of smaller
boats.
"Para" which in the Indian language means "river" is mostly covered by the
tropical rain forests of the Amazon, and the state is still very
underpopulated. But the state is very rich in mineral resources, and other
resources of the forests such as timber. Exploitation of the resources of
the state had led to conflicts between Ecologists and the Indians on the one
hand and Government and Private agencies, both legal and illegal, on the
other. Today more than 50% of the rain forests of Para are protected either
in Government or indigenous Indian reservations. The rich mineral resources of the state include iron, copper,
manganese, nickel, aluminum, tin, gold and gems and minerals. The types of
gemstones found in Para include the following :- diamond, emerald,
aquamarine, tourmalated aquamarine, chromin, chrysoberyl, citrine, topaz,
amethyst, opal and helvite. Except for diamond about which details of
reserves are available information concerning other gemstones are not
available.
Minas Gerais had been the main source of imperial and precious topaz in the
world, but small deposits of low grade topaz have also been found in the
Northern Brazilian State of Para. Thus the "Lua de Maraba" most probably
originated either in Maraba or in an area closer to the city of Maraba,
and hence was named the "Moon of Maraba" in order to reflect the origin of
the gemstone.
Characteristics of the gemstone
The original weight of the rough stone is not known, but when cut and
polished the finished gemstone had an enormous weight of 25,250 carats,
making it the second largest faceted topaz, as well as the second largest
faceted gemstone in the world.
Please click here to see the
list of famous faceted topaz greater than 1,000 carats in weight, arranged
in descending order of weights.
The cut of the stone is a perfect octagonal-cut, with dimensions of 18 x 15
x 10 cm. The stone is of perfect flawless clarity, and its color is a rare
gray color, making it perhaps the only one of its color and size in the
world.
©
Programa Royal Collections. Agrupación Europea de Interés Económico 2006
Color in topaz
Topaz occurs in a variety of colors such as colorless, gray, yellow, brown,
yellowish-brown, pale blue, light green, orange, pink and red. The
commonest colors in topaz occurring naturally are colorless, yellow,
yellow-brown, and pale blue and the rarest colors are pink and red. Except
in pink and red topaz where trace quantities of chromium act as a
chromophore absorbing light at a specific frequency and imparting color, all
other colors in topaz is caused by color centers. But, even for the
formation of color centers trace quantities of some impurities such as iron,
must be present. The iron atoms form an unstable species in the crystal,
which can absorb a visible photon of light and jump to an excited state. The
return of the unstable species from the excited state to the ground state
emits light in different regions of the visible spectrum, depending on its
frequency and wavelength. Such unstable species created are known as color
centers.
The presence of color centers in topaz make it ideal for color change either
by irradiation or heating. Pink and red topaz can be obtained by the heat
treatment of brown, yellow or orange topaz that contains trace amounts of
chromium or iron as impurity. Dark blue shades of topaz are produced by
irradiation followed by heating of colorless, pale blue, and yellowish
brown, and greenish-brown crystals. Smokey-grey, cinnamon-brown and
yellow-orange colors can also be produced by irradiation by controlling the
time of exposure to radiation. The "Lua de Maraba" however appears to be a
naturally formed enormous grey topaz as there are no reports to the
contrary.
History of the "Lua de Maraba" topaz
Origin of the topaz and its processing
The "Lua de Maraba" topaz was probably discovered in one of the topaz mines
in the northern Brazilian State of Para, in and around the city of Maraba.
The date of discovery, the weight of the rough stone and other details are
not known. The rough stone was cut into a perfect octagonal-cut, flawless,
gray-colored topaz weighing 25,250 carats, the second largest faceted topaz
and perhaps the second largest faceted gemstone in the world.
The topaz enters the Special Exhibition Gems
Collection of the Programa Royal Collections
After the Programa Royal Collections was inaugurated in Madrid, Spain in
1997, as an initiative of an European Economic Interest Grouping, and
regulated by the European Union, the "Lua de Maraba" topaz was purchased by
the PRC, and entered the Special Exhibitions Gems Collection, which consists
of 20 outstanding gems, brought together mainly because of their
extraordinary size, and exceptional quality. This collection has a total
weight of 117,000 carats, inclusive of the weight of the "Lua de Maraba"
which weighs 25,250 carats.
"Lua de Maraba" sometimes included in the
"Imperial & Noble" Monographic Exhibition
The "Lua de Maraba" while being a permanent part of the Special Exhibitions
Gem Collection, is sometimes included in the the Single Theme Exhibitions
under the category "Imperial & Noble" if a specific request is made by the
organizers for such a monographic exhibition. The "Imperial and Noble" is a
topaz collection under the Programa Royal Collections and perhaps the largest and most
comprehensive collection of topaz in the world. The collection consists of
54 gemstones of all sizes, cut and colors, with a total weight of over
90,000 carats. The collection also includes eight enormous topazes of more
than 1,000 carats in weight, varying in weight from 1,800 carats to 31,000
carats. The eight topazes in descending order of weights are 1)
El-Dorado-31,000 carats, 2) Lua de Maraba-25,250 carats, 3) Topaz
Amarelo-9,600 carats, 4) Topaz Azuli-8,225 carats, 5) Unnamed-4,202 carats
6) Unnamed-2,915 carats 7) Unnamed-1,833 carats 8) Unnamed-1,800 carats. The
"Imperial & Noble" single theme exhibition is accompanied by educational
display panels containing a wealth of information about the origin and
sources of topaz in the world, their chemical, physical and optical
properties, the different color varieties of topaz and their abundance in
nature, treatment of topaz to obtain rare color varieties such as intense
blue, pink and red, various uses of topaz throughout history, and
information on the background of each of the main gems in the collection.
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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
