This is the 7127th most frequent French word.
mines
"Faces" or "expressions" (plural of "mine").
Here, 'mines' refers to excavations in the earth where minerals are extracted, specifically coal.
Les mines de charbon sont dangereuses.
Coal mines are dangerous.
In this usage, 'mines' refers to facial expressions or demeanor.
Ses mines étaient très joyeuses aujourd'hui.
His expressions were very joyful today.
Here, 'mines' refers to explosive devices buried in the ground designed to cause harm.