A competent mine geology department does three reconciliations...

A competent mine geology department does three reconciliations based on mill actuals (the truth machine): Resource vs mill; Reserve vs mill; grade control (or mine claimed) vs mill. In doing this, the Resource (long term), Reserve (medium term) and short term (grade control) models are compared and various factors (or calls) are determined. In a well performing operation, grade control and Reserves should be within around 10% of actuals. It's not unusual for Resources to be waaay out. Call factors emanate from a variety of sources - survey misclosure, bulk density estimates, face sampling bias and what have you. If the grade control model is consistently out, that's a big problem. Usually there's time to fix Reserve misclosure and almost always time to fix Resource errors (unless it's a gross blunder), if mine staff are proactive enough. Gotta know when to hold and when to fold and be tough enough to issue corrections. But I bain't been underground at Abra and haven't been following it, so I dunno.