stope
noun
ˈstōp 
: a usually steplike excavation underground for the removal of ore that is formed as the ore is mined in successive layers
Example Sentences
Recent Examples on the Web That’s often the most unstable part of the stope, and generally higher on the mountain. 
National Geographic, 19 July 2019
National Geographic, 19 July 2019 Word History
Etymology
probably from Low German stope, literally, step; akin to Old English stæpe step — more at step
First Known Use
1747, in the meaning defined above