From Exploration Insights (https://www.explorationinsights.com/pebble.asp?relid=3577)

Watch for high grade smearing across low grade rock. Many companies that are having a hard time stringing together high grade continuity will push those grades out into waste, hoping to bulk up the deposit (on paper at least). Use the Drill Interval Calculator to check on the residual grade. I also find it useful to calculate what percentage of the grade is carried by what percentage of the rock.

http://www.corebox.net/drill_interval_calculator?data=8m,60 g/t,,,,2.25m,212.48,,,,

Residual Grade - 5.75m @ 0.334 g/t