At the Fazenda Marques property, the first of seven trenches is being dug along 2.7 km of the river bank. Each trench will be 5 metres wide, and together they will provide 26,000 cubic metres of basal gravels for processing in a new 15-tonne-per-hour heavy media separation plant.
Drilling in 1999 outlined 1.1 million cubic metres of basal gravels, while suggesting the potential for an additional 400,000 cubic metres.
The program is expected to take six months to complete.
At the adjoining Estaca property, farther upstream, large-diameter auger drilling is testing preserved meanders and terraces believed to host as much as 6.5 million cubic metres of the prospective gravels. The estimate is based on preliminary drilling carried out in 1999.
Once complete, the program will be followed by bulk sampling and trial mining to test for diamond content.
Meanwhile, trial mining is about to resume at Gamelas, the farthest-downstream of the three properties. This project is also the most advanced in Black Swan’s portfolio.
The company has received environmental permits to construct and operate a plant capable of treating 2,000 cubic metres of gravels per day — four times more than the pilot plant used in 1999.
Drilling last year delineated 3.6 million cubic metres of basal gravels in two paleo-channels with a combined length of 800 metres and a width of 150 metres. However, Black Swan says the property may host as much as 6.6 million cubic metres of the gravels.
Between September and December, Gamelas yielded 758.4 carats from 5,190 cubic metres for an average grade of 15 carats per 100 cubic metres. The stones averaged US$500-700 per carat (with one fancy weighing 16 carats, and another, 26 carats) and fetched an average US$8,125 per carat.
This followed the sale of 18 diamonds earlier in the year, when trial mining began. That parcel weighed 32.38 carats and included a 6.85-carat fancy that sold for US$5,000 per carat.
Black Swan can acquire a 51% interest in the Gamelas property by advancing it to commercial production and issuing shares plus warrants to the owner. The deal also provides for 90% of future cash flow to go toward repaying Black Swan’s costs, and entitles the company to 20% of the gross value of diamond sales in the meantime.
Elsewhere in the Coromandel region, small-scale bulk sampling is testing gravels overlying the Spider 1 kimberlite. The samples will be analyzed for indicator minerals in an attempt to identify the source of alluvial diamonds discovered a short distance downstream of a nearby river.
Meanwhile, in the Serra da Canastra kimberlite province, in the southwestern part of Minas Gerais, Black Swan is following up on the discovery of several indicator mineral anomalies with geochemical sampling. A few of the anomalies are near alluvial workings, and one recently yielded a pyrope garnet with a geochemical signature similar to diamond-bearing kimberlites found elsewhere in the province. Based on its physical characteristics, the garnet is thought to be within 3 km of its source rock.
In 2000, Black Swan plans to spend $3 million exploring its various diamond properties throughout Minas Gerais.
In related news, Black Swan has been unable to recover the proceeds from a 79-carat pink diamond sold earlier this year for US$2.2 million. A partnership in which the junior had invested US$2 million to acquire and market the stone is disputing the original deal and says it owes nothing to the company.
However, a director of Black Swan has agreed to pay the full amount by July 31 should the dispute remain unresolved. The director is the company’s largest shareholder and has pledged 23.1 million of his own shares as part of the payment.
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