AGTA GTC's Laboratory Update for November 8, 2005
In this message…
- Colombia's La Pita Mining District, October 2005
- Heat Seeker: UV Fluorescence as a Gemological Tool
- AGTA GTC on the Web
Figure 1. A small slice of paradise Rough and cut Colombian emeralds. Stones such as these have made Colombian emerald the standard by which all others are compared. Photo: Stuart Robertson/The Guide |
A visit to Colombia's La Pita Mining District, October 2005
Colombia is known as the country of the finest emeralds on earth. Long before the Spanish conquistadors arrived in the 16th century, the native peoples of Colombia mined emeralds. The first emerald that the Spanish conquerors held in their hand was from the Somondoco (now Chivor) deposit. Heavy fighting between the Indians and the Spaniards continued until 1559–60, when the Spanish conquerors finally took possession of the mines now called Muzo and Coscuez.Until 1848, only insignificant quantities of emerald were mined in Colombia. Until the middle to late 19th century, Chivor and Coscuez were closed temporarily, and anarchy reigned at the unregulated mines. In 1889 the Colombian Congress freed the slaves and nationalized most of Colombia's subsoil, and in 1905, the government declared itself owner of all mines. Licenses were individually distributed with various terms and conditions, and some mines were operated by the government. Parts of the Muzo and Cosquez Mine were reactivated, and Chivor rediscovered (Sinkankas, 1982).
In the middle of the 1990's, Colombian emerald production fell sharply due to various reasons, such as stagnant sources, the Japanese economic downturn, and the increased use of techniques to improve emerald transparency, which negatively impacted the reputation of emeralds. The La Pita deposit began significant production in 1998–99 and is being mined as a tunnel. Limiting production at La Pita itself has enabled the development of new tunnels in the same deposit such as Consorcio, Polveros, Casa de Lata, Las Cunas, Chizo and Los Totumos (Schwarz & Giuliani, 2002).
At approximately the same time, a new awareness among the Colombian emerald dealers led to many dialogues between them and major laboratories. The Colombian government aimed to open up an independent laboratory to improve the local market, improve exports and to control enhancement methods. In 1998, a World Emerald Congress with leading gemologists took place in Colombia and was deemed a success on many fronts. Since then, however, the government changed several times, a gemological lab was never opened and no other organized group of gemologists visited the Colombian mines.
Figure 2. Trip leader and emerald dealer Ron Ringsrud in his element, atop a mountain in Colombia's emerald mining district. Photo: Loretta Castoro |
Figure
3. Emerald cutting
in a Bogota workshop. |
To the mines
After a few exciting days in Bogota, where we visited museums, gemstone dealers and cutters (Figure 3) during the day and had tango lessons at night, we set off in three jeeps from one of the mine owners, Don Yesidh Nieto. Soon cold Bogota changed into a pleasantly hot and tropical landscape, and after more than seven hours, we ended up at the finca of another mine owner, Don Chepe Ortiz. His son Giovanni Ortiz attended us that evening. Early morning the drive went on for La Pita mine, another three hours from the Ortiz finca.
At La Pita, we finally had the "mining" feeling, when we entered the mine camp, got our rubber boots and hard hats, and went hundreds of meters into the tunnel of the Consorcio mine (Figures 4 and 5). An elevator brought us 60 meters under the ground to the active mining site.
Figure 4. Walking through a mining tunnel at the Consorcio mine in Colombia's La Pita district. Photo: Loretta Castoro |
Figure 5. Lore Kiefert with two miners 60 meters deep in the Consorcio mine in Colombia's La Pita district. Photo: Loretta Castoro |
Although we did not see one emerald at the mine, we were rewarded in the afternoon by being invited to attend a ‘reunion de dueños’ and a ‘remate’ – a meeting of mine owners and an auction among them for rough emeralds. We watched a ceremonial washing and display of 40 days of production at La Pita - 12,000 carats of emerald crystals. Later it sold, by sealed bid, for almost the equivalent of a quarter of a million dollars.
Next day brought a visit to the Polveros mine, smaller and also drier than Consorcio. Again we saw no emeralds in the tunnel but could sense their proximity within the fascinating alternation of shale, calcite and pyrite. After this we had to head back to Bogota, along the way visiting the picturesque village of Borbur and the town of Ubate, the latter of which is famous for its cheese.
Two more days of Colombian hospitality completed our stay with visits to Emerald Legend, a company of the Ortiz family, and another Tango evening. The next day we saw (and some rode) champion horses at Don Yesidh's ranch, followed by discussions on the emerald situation in Colombia, their need to attract foreign investment, laboratory services in their country, and about a new trust in the product – Colombian emerald.
In summary, our group spent a wonderful time in Colombia, thanks to Ron Ringsrud and his many Colombian friends. We were overwhelmed by the hospitality and never felt threatened. For us, Colombia was a safe place, and we can only hope more gemologists will experience this magical land.
Figure 6. The Gang of 10 The group assembled in Bogota. From left to right: Stuart Robertson, Robert Weldon, Loretta Castoro, Leslie Sherman, Lore Kiefert, Cindy Lawson, Starla Turner, Suzanne Martinez, Nata Schluessel, Roland Schluessel. Photo: Ron Ringsrud |
References & further reading
- Schwarz & Giuliani (2002) South America: Colombia. In "Emeralds of the World," extraLapis, English No. 2: The Legendary Green Beryl, pp. 36–45.
- Sinkankas, J., 1981. Emerald and Other Beryls. Chilton Book Co., Radnor, PA, 665 pp.
Heat Seeker: UV fluorescence as a gemological tool
Over the past few months the AGTA GTC's Richard Hughes has penned a number of short pieces discussing the use of SW UV fluorescence for unmasking heat treatment in corundum. These articles came about following RWH's plunge back into serious gemology in January 2005, when he joined the AGTA GTC.
While checking the SW fluorescence of a heated sapphire, he decided to call AGTA GTC technical advisor, John L. Emmett, to inquire about the cause of the chalky fluorescence in heated and synthetic sapphires. "Interesting that you should ask," Emmett replied. "I've been doing much thinking about that same subject of late." And so it was that RWH and JLE began sharing thoughts on this subject.
Hughes and Emmett have now produced a major stand-alone article on the subject. You can see it at the following link:
AGTA GTC on the Web
A number of clients have asked us to consider making our gemological bulletins available to a wider audience. Towards that aim, over the past few months we have built a website specifically for the AGTA Gemological Testing Center. It is now live and offers a complete archive of our e-mail bulletins, along with a full description of the lab and its services.
See it at www.agta-gtc.org or link from AGTA’s regular site, www.agta.org.
The new AGTA-GTC website offers the most up-to-the-minute gemological news, along with a full description of the lab and its services. |
