The original carats per hundred tons projections were based on the 218 drill cores carried out by the Brazilian state company around 1989 and the activity of the local miners.
The processing of that info indicated a range of 10cpht - 25cpht but I notice that the newstrack announcing the start of mining at Melgueira says the average is expected to be 20cpht.
As a ball park comparison, John Teeling at AFD says that 10cpht would make for a commercial diamond mine at their latest sight.
