A preliminary economic assessment on Karelian Diamond Resources Plc's Lahtojoki diamondiferous kimberlite pipe in southeastern Finland estimated that 2.11 million carats are recoverable, giving it a gross value of US$211 million.

The study, using a price of US$100 per carat, pegged a net present value, discounted at 8%, of US$39.1 million, a 55% internal rate of return, and a nine-year life of mine.

The capital cost is estimated at US$22 million, including process plant costs of US$14 million, infrastructure costs of US$3 million and working and sustaining capital costs of US$5 million.

The payback period is anticipated to be two years, the company said Aug. 1.

Based on the results, the company is recommending the development of an open pit operation.