Whaler,

I believe the standard pattern is a core every 25 meters. In a grid that give each core an area of 25x25. That area times the concentratins and footages from the core gives the estimate for that core.

Standard practice prbably doesn't allow for an area greater than that to be asigned to a core if there is no adjoining core.

May be a little overstated in the case of cores closer than 25 meters.

Still a good exercise for an estimate.