Origin of name
The Guinness Emerald Crystal discovered in the Coscuez emerald mines is one
of the largest gem-quality emerald crystals in the world, and is the largest
emerald crystal in the collection of emeralds belonging to the Banco
Nacionale de la Republica in Bogotá, the capital city of Colombia. The
origin of the name Guinness is not known, but the elongated, 1759-carat,
bright green crystal undoubtedly had all the credentials to enter the
Guinness book of world records as the largest gem-quality emerald in the
world at least for some years until it was surpassed by other larger natural
emerald crystals.
Characteristics of the gemstone
The 1759-carat "Guinness Emerald Crystal" was at one time the largest
natural emerald crystal in the world, and is still preserved in its natural
crystalline state, at the Banco Nacionale de la Republica in Bogotá.
Emeralds crystallize in the hexagonal crystal system resulting in elongated
or flattened hexagonal prisms with pinacoidal terminations. But, the
"Guinness Emerald Crystal" is an exception, as it is dihexagonal or
twelve-sided, also known as dodecahedral. The exact dimensions of the
crystal are not known, but the crystal is undoubtedly elongated, with its
length between 2 to 2½ times greater than its diameter.
The color of the emerald is a bright green color with a slightly yellowish
undertone, characteristic of emeralds from the Coscuez emerald mines. The
diaphaneity of the emerald is translucent, and some cracks and
fissures are visible at the lower end of the crystal. Emeralds from Coscuez
are generally more included than those of Muzo and Chivor mines.
Crystal characteristics of
Coscuez emeralds
Certain characteristic features of the crystals and the matrix in which they
occur can be used to identify the source of the emeralds from the three main
mines of Colombia, the Muzo, Coscuez and Chivor mines.
The most characteristic feature of the Coscuez emerald crystals is their
frequent occurrence in aggregate type of formations with multiple
terminations. The aggregates have a step-like appearance and sometimes a
tabular appearance. It is not known whether the "Guinness Emerald Crystal"
of Coscuez origin, is also a constituent part of a larger aggregate of
crystals. The emerald crystals from Muzo and Chivor do not form
clusters or aggregates, however the Muzo emeralds tend to be shorter, while
the Chivor emerald crystals are much longer in length.
Color differences and inclusions in the
emeralds from the three sources
Muzo emerald crystals tend to have a more saturated color than either
Coscuez or Chivor emeralds. Muzo emeralds have a deep herbal-green color.
The Coscuez emeralds are generally yellowish-green in color, whereas the
Chivor emeralds have a bluish-green color. The Chivor emeralds have a
lighter color than either Coscuez or Muzo emeralds. But, using color alone
one may not be able to predict the source of the emeralds correctly.
The Chivor emeralds generally have much less inclusions than either Coscuez
or Muzo emeralds. The Coscuez emeralds have diffused gardens and inclusions,
but have good color and brightness. The Muzo emeralds also have inclusions
but are less apparent due to the deep herbal-green color. Muzo emeralds with
less inclusions have good transparency.
Matrix characteristics of the three different
sources
The matrix in which the emerald crystals occur in the three different
sources have common constituents. These constituents are black and grey
shale, white and grey calcite, and pyrite. But these constituents are found
in different combinations in the matrix of different sources.
In the Coscuez matrix black shale is found in combination with either grey
calcite or a brown layer of iron oxide, or sometimes only a grey calcite
matrix. Thin veins of pyrite run through the black shale. However, the most
predominant characteristic of the Coscuez matrix is the presence of grey
calcite.
In the matrix of Muzo emeralds black shale is combined with pure white
calcite, crystallized pyrite and sometimes clear quartz. White calcite and
crystallized pyrite are the identifying characteristics of this matrix.
In the matrix of Chivor emeralds grayish shale is combined with grey calcite
and layers of iron oxide and crystallized nodules of pyrite. The matrix is
fragile and has brown stains caused by iron oxide. Because of the fragility
of the matrix, fewer specimens with the matrix still intact are found in
Chivor.
History of the gemstone
The Coscuez emerald mine -
source of the Guinness Emerald Crystal
The Coscuez emerald mine where the "Guinness Emerald Crystal" was discovered
is one of the three ancient and historic mines of Colombia, which were
exploited long before the arrival of the Spanish Conquistadors, the other
two being the Muzo and Chivor mines. Both the Coscuez and Muzo emerald mines
are situated in the Boyaca district at the northwestern end of the NW-SE
emerald belt of the Andes mountains known as the "Cordillera Oriental." The
Coscuez mines are situated just 10 km north of the Muzo emerald mines, and
share many geological features, even though the Muzo mines are the best
known, with an international reputation as one of the most prolific emerald
mines in the world. The output of the Muzo mines declined over the years,
and today the Coscuez mines have taken the place of the Muzo mines producing
almost 60% of the annual emerald output of Colombia.
Coscuez is an emerald city, nestling between the craggy mountain peaks of
central Boyaca State. Both the Muzo and Coscuez emerald mines are exploited
by the open-cut mining methods creating open-shafts and open-pit mines. The
Coscuez mines had produced some of the world's significantly large emerald
crystals, such as the 7,000-carat "Emilia Emerald Crystal," perhaps the
largest emerald crystal ever discovered in the world, and the 1,759-carat
"Guinness Emerald Crystal," the subject of this web page. Coscuez, is also
the home of Victor Carranza, the renowned emerald mogul who is one of
Colombia's richest men and discovered his first gem at the age of 10 years.
Factors that militate against the development
of the emerald industry in Colombia
Colombia, which is undoubtedly the world's leading producer of high quality
emeralds, had produced over 60 % of the World's annual output of emeralds.
About 1.6 million acres of mountainous land have been identified by
geologists as having potential emerald veins, but only about 7,000 acres of
this land had been mined since ancient times. Among the factors that
militate against a more comprehensive and scientific exploitation of these
deposits, are the unstable political climate created by left-wing guerilla
activities, that discourage foreign investment, the interference of
left-wing guerillas and drug traffickers in mining activity, more as a means
of laundering drug profits than a desire for the potential wealth that
emerald mining could generate. The legal miners led by Victor Carranza
fought back after forming private armies, that led to the death of more than
3,500 people during the so-called "green wars" which eventually ended
after the declaration of an informal truce in 1990. Major foreign investment
is needed for the development of Colombia's emerald industry, and so far
only the Canadian companies have invested heavily to develop the ancient
Chivor mines using state-of-the-art mining techniques. Another factor that
had discouraged new investment is the speculative nature of emerald
mining, in which it has been impossible to confirm the presence of emeralds
without a major excavation. Thus the risk factor involved in mining seem to
have discouraged major investment. The use of satellite technology to map
out potential gem-bearing areas seem to be a possible answer to this
dilemma.
Even the limited mining activity that had taken place in Colombia so far,
doesn't seem to have benefited the country so much, as billions of dollars
worth of emeralds had been smuggled out of the country without taxes being
paid. Besides, most of the gemstones exported legally out of the country are
in the rough form which is less profitable than exporting cut and polished
stones either as loose emeralds or set in different forms of jewelry.
Strip mining in Coscuez replaced by tunneling
The Muzo and Coscuez emerald deposits have been found to be around 32
million years old, and are much younger than the deposits found in Chivor
which are around 64 million years old. In both Muzo and Coscuez mines strip
mining and open-shaft mining have been replaced by tunneling. The Coscuez
mines are situated in the same mountain range as the Muzo mines. The main
material found in the mines is gray shale, unlike the Muzo mines, where it
is black shale. Tunneling in the Coscuez mines starts 500 meters below the
peak of the mountain, and the main tunnel travels about 1,500 meters
straight into the mountain, with side shafts following the indicators of
albite. The output from Coscuez has many fissures that might require oil
treatment, a condition referred to as "porus."
Emerald output for Colombia for the year 2000
Colombia is the world's major source of high-quality emeralds producing
50-60 % of the world's total exports. For the year 2000 the total emerald
production in Colombia was 8.45 million carats, which represented an
increase of 24 % compared with that of 1999. The total value of the exports
was $94.3 million.
Preservation of the Guinness
Emerald Crystal by the Banco de la Republica of Colombia
The Banco de la Republica which was constituted as the
Central Bank of Colombia on July 25, 1923, plays the role of banker to the
banks, as any other central bank in any part of the world. Besides
performing normal functions of a central bank such as the issue of legal
tender, foreign exchange functions, administration of international
reserves, serving as the government banker, fiscal agent and trustee,
certain credit functions as laid down by Law 31, the bank also performs
the crucial function of promoting scientific, social and cultural
development of the country through the creation of foundations designed to
select, finance and otherwise stimulate investigations in the field of
science, technology, anthropology, archaeology, education, health and
humanities. In keeping with this objective the bank has played a part in
efforts to rescue and preserve the cultural patrimony as well as in efforts
to stimulate its continued development through the creation and
administration of libraries and specialized museums through out the country.
Two such institutions are the the internationally renowned Gold Museum known as "Museo de Oro" and
the "Luis Angel Arango Library." The acquiring and preservation of
significantly large emerald crystals discovered in the mines of the emerald
belt of Columbia, such as the "Guinness Emerald Crystal" is undoubtedly in
conformity with the policy of the bank in rescuing and preserving the
cultural and natural heritage of the country. It is said that five unnamed
large emerald crystals from Muzo have also been acquired and preserved
by the Banco de la Republica weighing between 1,100 carats and 1,796 carats.
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References
1.The Coscuez Mine - A Major Source of Colombian Emeralds
- Ron Ringsrud, Gems & Gemology, The Quarterly Journal of GIA, 1986, Volume
22.
2.Colombain Emeralds - by Gary Roskin - JCK Jewelers
Circular Keystone, Jan. 1998.
3.Website of
the Banco de la Republica
4.The Mineral Industry of Colombia - by Omayra
Bermudez-Lugo.
5.The Emerald Deposits of Muzo Colombia -Joseph E. Pogue. Transactions of
the American Institute of Mining Engineers, Vol LV, 1917.
