---ADDS BROKER COMMENT---
The JORC compliant inferred resource rises 35% to 1.477mln carats, while bulk sampling has led to a 37% increase in the grade to 165 carats per hundred tonnes.
Meanwhile, the diamond price model now puts the value of stones unearthed at between US$145 and US$270 per carat and values the resource at up to US$290mln.
Broker Daniel Stewart said: “It is unquestionable that the increase in contained carats will have a positive impact upon Tongo’s economics.”
Chief executive Karl Smithson pointed out that further potential exists as the project also encompasses three parallel kimberlite dykes which form part of the Tongo dyke swarm.
This includes the one-kilometre long Dyke-4, which has previously been bulk sampled and returned a diamond grade estimate of 110 carats per hundred tonnes and an estimated average diamond value of US$140 per carat.
Last month Stellar said trial mining of its Baoulé kimberlite pipe in Guinea had exceeded hopes with a number of large stones uncovered.
The first ore processed yielded 196 carats in total, or 17 carats per hundred tonnes – which was well ahead of the minimum expected grade of 13 carats per hundred tonnes.
Within that Stellar unearthed octahedrons of 5.5 carats and 5.1 carats alongside stones of 3.1, 1.9, 1.3 and 1.2 carats. Overall, half of the diamonds found were of gem quality.