Cluff said the recently discovered layer of higher grade gravels has been further sampled with 80 tonnes of unscreened gravels yielding a grade of 53 carats per hundred tonnes.
"This is twice the concentration of diamonds previously reported," Cluff said.
A total of 419 gem quality diamonds were recovered, with an average of eight stones to the carat.
The stones are mostly yellows, with the largest being a 0.75 carat pale yellow triangular stone (macle).
Cluff said four of the stones have gold grains growing on them, one grain being about half a carat in weight.
In addition, 1.8 grams of gold were recovered from the sample, all grains greater than 1.2 mm in size, as any finer gold would not have been captured in the concentrates tested, it said.
Cluff Resources shares were 0.2 cents higher at 4.3 cents in afternoon trading.
