So far, a total of 20,047 tonnes of 35,688 tonnes of diamond bearing gravels mined have been processed yielding 47.64 carats.
Based on what's been processed so far, the grade was 0.278 carats (ct) per hundred tonnes (cpht), while the NI43-101 estimate was for 0.12 cpht with an average stone size of 1.22 carats.
Meanwhile, the firm's first diamond sale closed on July 28 and the precious gems were sold at an average of US$2,480 per carat, while the highest price received was USD$6,016 per carat and the average stone size was 3.28 carats.
To give some idea of carat size and rarity, fewer than one in a million mined rough stones are large enough to produce a finished 1 carat diamond.
The Toronto-listed mining group said it was "pleased" with the higher than expected grade and average stone size recovered.
Risks to advancing the project, in addition to grades recovered and the chance of theft, is the ability to maintain the tonnage throughput target set of 122,000t per month but Tango said it could mitigate this by using another technology and additional earthmoving and mining equipment.
Oena is a 8,800 hectare mining right along the Orange River in a well-established alluvial diamond-mining province known to produce high quality and large sized diamonds.
Shares are unchanged at C$0.02.