136
interval. The Qa/Qc protocol consists of 5% samples inserted in all batches, such as: blanks,
standards, duplicates and includes both DDH and RC. The grade control drilling usually
covers up to 12 months in the mine plan.
Checking whether both datasets have similarity in terms of Nb 2 O 5 grade, P-P plot was
used to compared both distributions in an area predefined covered by exploration and grade
control drilling. The results show that both distributions have a very similar shape, despite
the DDH and RC have a quite different sampling support.
Figure 1. (Left) P-P Plot compares the two distributions, (Center) Nb 2 O 5 sample histogram for DDH,
and (Right) Nb 2 O 5 sample histogram for RC, all in the same predefined area.
Figure 2. Sample histogram of the target variable Nb 2 O 5 , Fe 2 O 3 and TiO 2 , DDH and RC data.
Figure  3. Cell de-clustering results for Nb 2 O 5 data for the Boa Vista fresh rock samples within the
mineralized envelope.
Table 1. Matrix correlation between the interest target
variable Nb 2 O 5 , Fe 2 O 3 and TiO 2 , DDH + RC data.
Variable
Nb 2 O 5
Fe 2 O 3
TiO 2
Nb 2 O 5
1
0.73
0.45
Fe 2 O 3
0.73
1
0.65
TiO 2
0.45
0.65
1
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