A mass of unmineralized wall rock that has broken off and become incorporated into a vein or fault zone. When a vein bifurcates around this barren rock and rejoins on the other side, the vein is said to take horse. Miners must often drill and blast through a horse, which dilutes the ore grade and complicates extraction.
The main lode splits around a massive limestone horse on the fourth level, dropping our recovery grade for the week.
Hitting a horse usually means a temporary drop in production, as the crew has to move barren waste rock to get back into the pay dirt.
Also heard as
- horse of rock
Related terms
Country rock
The pre-existing, non-mineralized rock that surrounds and encloses an orebody or igneous intrusion.
Lode
A defined vein or tabular deposit of valuable metallic ore embedded within barren rock.
Gangue
The commercially worthless rock or mineral matter mixed with valuable ore.
Fault
A planar fracture in a rock volume across which there has been significant displacement.