The mass rock is in general hard and requires breaking prior to handling by mining equipment. ANFO provided by
CADEX is the main explosive used to blast overburden. The powder factor (PF) varies from 0.25 to 0.50 lb./yd3 (150
- 350 g/m3) depending on rock’s properties. Two initiation methods are used: by detonating cord (0.026 lb./m) and by
electrical sequential method for area subject to environmental constraints. The delays are of 25 ms between blast holes
and about 100 ms between rows. The stemming is performed with the drilling cuttings on about 3.5 m (11.48 ft) length
from the top. A typical overburden blast is shown at Figure 5.