Etruscan overcomes Tirisano problems

Although it is still behind schedule, the fledgling Tirisano alluvial diamond mine in South Africa appears to have turned the corner.

Etruscan Resources (EET-T) advanced Tirisano to production in November 2002 and expects to process 100,000 tonnes of gravel monthly, resulting in a projected 19,200 carats in each of the next 10 years. Just over a month’s worth of gravels had been processed by the end of March 2003.

The delays stem from difficulties in treating the deposit’s volumous clay-rich yellow gravels. Yellow gravels make up 85% of the known resource of 10.4 million cubic metres.Modifications to the plant were completed in February 2003, and it is now running smoothly. More scrubbers will be added over the remainder of the year to increase throughput and availability rates.

As part of the teething process, Etruscan mined 100,000 tonnes from the eastern margin of the deposit in 5,000-tonne stages. The average head grade was 2.72 carats per 100 cubic metres, which compares favourably with the resource grade of 2.9 carats per 100 cubic metres.

The process also has helped confirm life-of-mine predictions for realized price and revenue: 1,754 carats sold to the end of March fetched 7% more than expected, averaging US$429 per tonne, and mining revenue is up 14% from expectations, at US$6.49 per tonne. Some material was mined outside the control block, and 259 carats mined inside it were to be sold in early April.

Meanwhile, Etruscan has begun final engineering and design studies on the feasibility of twinning the existing plant. The existing one can handle 4,000 tonnes of gravel per day.

According to Gordon, the known resource is sufficient to feed both plants for eight years. The original resource of 8.2 million cubic metres grading 2.9 carats per 100 cubic metres was expected to feed the existing plant for about 10 years (T.N.M.,, March 10/03).

Meanwhile, drilling in the Blue Gum Tree area, where a separate operation is envisaged, has outlined two sinkholes similar to the one hosting the Tirisano deposit. Sinkholes are topographic depressions in the underlying karst bedrock formed by groundwater flow; they provided natural traps for subsequent fluvial gravel deposition.

A resource estimate is expected in the coming months, as is an updated resource and initial reserve estimate for Tirisano.

When the mine opened, Etruscan predicted Tirisano would generate about US$77 million in revenue and US$27 million in after-tax income over 10 years. Since then, an additional 4 million cubic metres have been outlined.

Etruscan has a 75% stake in Tirisano, with the remainder held by Mountain Lake Resources (MOA-V).