Botswana Diamonds said sampling work at its Thorny River project in South Africa has failed to produce enough diamonds for an economic modelled diamond valuation.
“We recovered insufficient diamonds, particularly the bigger sizes, to produce a valuation which could be used in economic modelling,” said company chairperson John Teeling.
“This will be addressed. The next work programme will include options to determine the economic viability of the resource.”
Botswana Diamonds said a sample equivalent to 305.38 dry tonnes of kimberlite and host rock was taken late last year from a 42-metre trench on Frischgewaagt, along the strike of the dyke.
A total 512 diamonds weighing 62.883 carats were recovered from the sample following treatment through an independent integrated processing facility, it said.
The company also said that the parcel average to be $89 per carat in the +11-diamond sieve class, which compared favourably with the $77 per carat achieved in the same diamond sieve class from a 2015 sampling campaign.
However, the diamonds recovered were not sufficient to produce a modelled diamond valuation, and thus the 2016 valuation of $259 per carat continues to apply, it said.
Botswana Diamonds said that gem quality diamonds comprised about two thirds of the value of the parcel and less than 40 percent of the parcel illustrated medium or high fluorescence.
Also less than 10 percent of the stones were chipped or broken.