坑内 こうない 炭鉱 たんこうではありませんでした
kō nai horitankōdewārimasendeshita

Noun
Desu Copula

The polite, past negative form of 坑内掘り炭鉱

1. Was not a pit coal mine.; Was not a coal mine dug in a pit.

Past/Perfective
Negative
Polite
Formal Register