Which of the following is a cause of fly rock?

• A. Using low-quality blasting caps
• B. Excessive explosives
• C. Improper timing of detonations
• D. Poor ore grade

Answer: (B)

Excessive explosives create too much energy and gas pressure for the rock and the blast cavity to contain, so rock fragments are hurled outward beyond the intended breakage area. When the charge is larger than necessary, the unleashed energy pushes pieces of rock away from the face, producing fly rock. The other factors listed—initiation reliability, timing, or ore grade—don't directly cause rock to be projected like this; they can affect detonation and fragmentation in different ways but not the core mechanism of overloading the blast with energy. To prevent fly rock, use the minimum effective charge, proper stemming, correct burden and face geometry, and adequate blasting mats and safety distances.