Bungy, the micro diamonds is usually for drill results, bulk...

Bungy, the micro diamonds is usually for drill results, bulk sampling should produce some diamonds (if there). You would want results that are in the ballpark of what is required for mining or at least worth a further larger sample.
Usually you would want at least 10 cts/100tonnes, average around 0.25.
From memory Argyle was around 10ct per tonne and I think Mothae is less than 5ct per 100tonne.

Next measure would be your size distribution with the average diamond around 0.1ct, Argyle was closer to 0.05ct avg, Merlin, Ellendale closer to 0.4ct avg.
% Gem would be then looked at, though this can be a bit loose as there is no set standard of what is Gem quality. Colour distribution would also be looked at, generally you would want at least 1000cts of diamonds to be reasonably confident in a $/ct valuation, the biggest issue is if a large diamond is produced (or not) that can significantly affect the results.