A localized area in an underground mine where the roof and floor rock converge, pinching the mineral seam to a fraction of its normal thickness or extinguishing it entirely. This is usually caused by structural squeezing from tectonic forces or ancient stream channels scouring away the peat before it became coal.
We hit a nip-out on panel four and had to drive through fifty feet of barren rock to find the seam again.
Also heard as
- pinch-out
Do not mix it up with
- Washout: A washout specifically implies erosion by an ancient stream, while a nip-out can also be caused by structural squeezing.
Related terms
Thill
The layer of rock or clay lying immediately beneath a coal seam.
Roof
The layer of rock located immediately above an underground excavation or mineral seam.
Washout
A channel in a coal seam or orebody where the original deposit was eroded and replaced by barren sediment.
Pinch-out
A geological formation where a rock layer or orebody tapers until it disappears.