Hey Crusty,Concentrate grade can be the same, but unlikely IMO....

Hey Crusty,

Concentrate grade can be the same, but unlikely IMO. It all depends on the metallurgical recovery during flotation. They have published 91%. By my calcs this should be 4% up (from 87%) if it means same volume of concentrate at same grade.

6.337Mtpa/[email protected]%=92kt Zn @91% recy=84ktpa contained Zn.
Working backwards from 84ktpa of recovered Zn to estimate original recovery:
5.856Mtp/[email protected]%=96kt Zn
To maintain grade the original recy must have been 87% to get 84ktpa of contained Zn.

I'm not sure what the original published recy was, but I just found this (Gunslung Nov 2006):

Mine life 12 years
Ore Reserves 6.3Mt
Ore per Vertical Metre 10,000 t
Plant Throughput 525,000 tpa
Head Grade 14.5% Zn!!!!!!!!!
Concentrate Production 132,000 tpa
Concentrate Grade 53%
Zn Recovery 92%!!!!!!!!!!!!
Metal Production 70,000 tpa Zn

In November 2007 more slinging with a 12.5 years mine life.

Anyway - you might be right DC, if the recovery was always 92%, then the product grade should be up to 56.5% not 53.8%.

Can anyone confirm the last published recovery at less than 91%?

Oh well back to the day job........