Open Pit Gold Mine Depth

Originally posted by jezzathegeo ↑

No, read what I wrote. You're talking about mill constrained operations - the orebody is too small to sustain the fixed and operating costs of the mill that some idiot has built. Somebody hasn't followed the SS, PFS and FS process and if they have, then they've "tried to make it work".

There's a spectacular train wreck in progress at the moment where a 3Mtpa mill with one chingon weird configuration was constructed without a FS on a 30Mt @ 1% (and that's being chingon generous!!) orebody. Apparently the Board thought it would be really groovy to have a 10 year mine life - without any evidence. A vanity project. When eventually released, the "Reserve" estimate indicates that the thing don't makea da money for six of those ten years. This lot haven't yet released last years' financials, but it looks like it ain't never madea da money.

It's all about scale. The Yanks have what's called Taylors Law, an empirical regression published by the USGS and updated from time to time that relates mill size to orebody size. It's skewed toward Nth American operations, which run in different geology to that in Oz, but it's not a bad start. I prefer to take tonne-grade curves (preferably optimization results) and add in capital and operating cost, varied against mill size and capital. Simple if you know how on an Excel spreadsheet.

There's a really good reason why off-the-shelf mills come in 1, 1.5 and 3Mtpa flavours - its because the capital and operating costs of these plants suit most economic orebodies. If you want something bigger or with a weird configuration, then it's exponentially more expensive - just ask CITIC Pacific.

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Yep I keep wondering how the 1 gram a tonne mines will work , Evolutions Cowal mine seems to do ok , which seems to be what Golden road is modelling their remote WA mine on 270k oz per year at 1.2 gram a tonne feed that means around 7.7mtpa but no AGL grid energy supply to rely on and yet are expecting AISC of $950.00 , developer Echo also with the Bronzewing plant also have a similar low grade mine analogue which hs failed at that plant about 3 times now (View , Navigator ) since the the Rabbi Gutnick found the ore body .
Yes with the ginormous plants up you can not find an old Allis chalmers 7mtpa ball mill off the shelf , if needing a replacement for a ring gear fracture so plant is dead for 3 months waiting for a replacement ring gear , but if looking for a 1 mtpa ball/SAG mill they are available and can ship it in one piece out of bone yard in Kal , there are dis-economies to scale when it comes to maintenance on large plants .