Nevsun gets high gold grades at Bisha, but steady on guidance
Nevsun published production figures today that suggest gold grade from mining and milling in transitional ores is stronger than it had anticipated.
Author: Kip Keen
Posted: Monday , 09 Jul 2012
HALIFAX, NS (MINEWEB) -
Nevsun Resources (TSX, AMEX: NSU) once again credited higher than expected grades in transitional oxide gold ore at its Bisha gold-copper-zinc mine Eritrea for strong production.
It is a welcome bit of good fortune for Nevsun, which earlier this year had to cut guidance at Bisha in half to around 200,000 ounces gold before readjusting it back up.
In the last quarter Nevsun said it had started to mine transitional ore between gold-rich oxides and copper-rich supergene zones at Bisha and that the gold grade therein was much higher than expected.
It had been tough for Nevsun to model grades in the the transitional zone in past resource estimates at Bisha because the in-between-ore was not drill friendly. Core recovery in the transition zone was poor, making it difficult to accurately estimate grade. Further, there was also the question of how easy it would be to recover the gold in the transitional ore, which Nevsun describes as "acidic" or "soap" ore.
But this year Nevsun is showing that grades and recovery are good in the acidic/soap ore. "In last quarter we had positive reconciliation from acidic/soap ore that were not in resources due to their sandy, irregular nature," said Cliff Davis, Nevsun President and CEO, in an email. "This quarter we confirmed metallurgical recovery of acidic/soap ore."
Thanks in part to this development, in the first quarter this year Nevsun made a nice looking readjustment to the then just diminished gold guidance, boosting forecast production in 2012 to between 240,000 ounces to 260,000 ounces gold. In the first quarter Nevsun produced 82,000 ounces gold, milling 430,000 tonnes _at_ 6.58 g/t gold and mining 349,000 tonnes _at_ 4.71 g/t Au.
Now production figures are in for the second quarter and they are even better than those in the first. Nevsun produced 87,000 ounces gold, milling 465,000 tonnes _at_ 6.93 g/t Au. It mined 500,000 tonnes _at_ 6.04 g/t Au.
Nevsun isn't, however, making any more changes to its 2012 gold outlook - at least not yet. Nevsun said it would revisit guidance in August after July production figures are in and it releases financial results for the second quarter.
One thing to watch for this month is a resource update. Expected out this month, Nevsun said it will report for the first time resources from the Harena satellite deposit, which is near to Bisha. Importantly, Nevsun said it now has a mining license for the deposit, which has gold in oxides, and that it planned to mine Harena and blend material from it with Bisha ore throughout 2012.
The resource should help answer the question, how much will Harena contribute to Nevsun gold production?
To give a general picture of the deposit, Nevsun has said it drilled Harena oxide and sulphide mineralization over widths between 5 and 35 metres over a 400-metre strike length. Among numerous sub-gram hits over intercept widths in the 5- to 10-metre-long range, there have been some eye-catching drilling results including 24 metres _at_ 1.63 g/t Au and 31 metres _at_ 2.41 g/t Au.
Of course, in the grand scheme Bisha is really about copper and zinc. Mining of gold rich oxides at Bisha Main is winding down as Nevsun moves into a copper production phase, slated to begin mid-2013 (prestrip is well underway). Mining of zinc-rich ore will follow suit from deeper sulphides.
Received on Mon Jul 09 2012 - 13:54:17 EDT