noun
host rock; country rock; parent rock
Geological term for the rock surrounding or containing a mineral deposit, ore body, or intrusion. 'Gangue' refers specifically to the valueless material in an ore deposit.
この鉱床の母岩は花崗岩である。
The host rock of this ore deposit is granite.
母岩と鉱脈の境界を調べる。
Examine the boundary between the country rock and the vein.